VTechWorks Repository :: Browsing by Author "Eaton, John L."

Browsing by Author "Eaton, John L."

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Aspects of Hylotrupes bajulus (L.) biology in Virginia (Coleoptera: Cerambycidae)
Cannon, Kevin Francis (Virginia Tech, 1979-04-09)
The significant results of this research were: 1) A laboratory colony of H. bajulus was established and information on the N. A. biotype was collected. At this time it is too early to make any significant statements of comparison between European and N. A. biotypes. However, preliminary results indicate that the mean number of eggs per female, and the size and longevity of N. A. adults appear different than European beetles; 2) Outdoor survival studies of the larvae indicate that H. bajulus can live under natural conditions in Virginia's varied climatic regions. Over the course of two years 27 adults have been collected in such field conditions as fence posts, outhouses, screen windows, building exteriors, and free flying in open fields. This information, along with survival studies, strongly suggest the presence of natural populations; 3) The environment in which H bajulus larvae are located greatly affects its chances of survival. Larvae in attics can survive the fluctuating environmental condition, but growth and development are prolonged and potential structural damage minimal. Under these conditions H. bajulus larvae are more likely to undergo natural mortality over several years. In optimum (stable) conditions H. bajulus will increase their feeding and development. Under these conditions infestations that are left unchecked may lead to serious structural damage and reinfestations.
Aspects of the biology, behavior, and economic importance of Camponotus pennyslvanicus (Degeer) and Camponotus ferrugineus (Fabricius) (Hymenoptera: formicidae)
Dukes, John (Virginia Tech, 1982-05-12)
Aspects of the behavior, biology, and economic importance of carpenter ants were examined. The overall objectives of this study were to determine the economic importance of carpenter ants, and to extend the data currently available on two of the most common and economically important species in the U.S. A survey for the economic importance of carpenter ants indicated that carpenter ants are considered a serious pest by homeowners. The results show that 90% of the homeowners who requested control for carpenter ants during 1980, paid more than $25 for carpenter ant control. The presence of detectable damage was not the definitive factor in the decision to request control. Camponotus ferrugineus and C. pennsylvanicus are similar in their colony foundation and biology. C. ferrugineus required 54 days to produce the first brood and there were 18 workers, including one intermediate worker, in the first brood. Queens of C. pennsylvanicus required an average of 46 days to rear the first brood. Ad libitum feeding did not have a significant effect on colony founding in C. pennsylvanicus. Two queens reared their first brood under artificial light. Food preference studies of C. pennsylvanicus and C. ferrugineus indicated that these two species have similar food preferences. Although honey was preferred to most foods tested, it may not supply sufficient nutrients to ensure proper colony nutrition. C. pennsylvanicus has become well adapted to man-made structures. Some foraging ants are present year round. C. pennsylvanicus optimizes its foraging by exploiting indoor and outdoor foraging sites. The division of labor during nest construction may be based on subcaste. Major workers appear to be responsible for most nest-building in mature colonies.
Aspects of the morphology of the ovipositor of Hylotrupes bajulus (L.) (Coleoptera: cerambycidae)
Mares, Joseph Thomas (Virginia Tech, 1984)
Hylotrupes bajulus (L.) is a serious pest of seasoned softwoods. The female oviposits in the cracks and crevices of the wood, and the larvae can survive and feed in the wood for 2-10 years. The female H. bajulus has an elongated ovipositor comprised of the modified abdominal segments 8 and 9, intersegmental membrane 8/9, and pair of distal gonostyli. When not in use, the ovipositor is retracted within abdominal segment 7. The 8th abdominal segment forms the proximal end of the ovipositor. An internal apodeme attached to the base of the 8th sternite allows for extension and retraction of the ovipositor. The intersegmental membrane 8/9 makes up half the length of the ovipositor. The 9th abdominal segment, along with the gonostyli, comprise the dist3 l part of the ovipositor. The 9th sternum is split along the midline to form a pair of hemisternites. The gonostyli are comprised of basal coxites and apical styli. The gonostyli are the only remnants of the appendicular oviocsitor. Several types of sensory receptors are found on the ovipositor. Segment 8 has both long tactile hairs and short trichoid sensilla. Intersegmental membrane 8/9 has no vi sible sensory receptors. Segment 9 has campaniform receptors and short trichoid sensilla. The gonostyli have several types of sensory receptors including long tactile hairs, medium trichoid ser..silla, short trichoid sensilla, and basiconic receptors. The long tactile hairs and campaniform receptors are innervated by a single dendri te, thus functioning as mechanoreceptors. The medium trichoid are innervated by three dendrites, two of which extend into the lumen of the receptor. The short trichoid sensilla are innervated by five sensory neurons. The basiconic receptors are innervated by 1-3 dendri tes, depending on the type and location of the receptor. All three types of sensilla function as contact chemoreceptors, and may provide information on the suitability of the oviposition substrate.
Biological control agents of soybean insect pests in the Tidewater area of Virginia
Eaton, Alan Tucker (Virginia Tech, 1975-01-05)
The species of biological control agents which affect soybean pests in the Tidewater area were investigated, and their relative values were determined. Two pentatomids, Podisus Macu1iventris Say and Stiretrus anchorago F., were the only significant bio-contro1 agents which attacked the Mexican bean beetle, Epi1achna varivestis Mulsant. Thesepredators were not able to hold the pest population in check. A parasitic fly, Trichopoda pennipes F. was the only important biological control agent which attacked the green stinkbug, Acrosternum hilare (Say). Host and habitdt preferences of the fly suggested the presence of two strains in Virginia. Distribution of the fly was very uneven. Fungal disease was found to be an important control agent of many (larval) Lepidoptera. It was the most important control agent of Plachypena scabra (F.). P. scabra was also controlled by predation and parasitism. Nine parasites attacked the larvae and pupae. No effective biological controls were found for the corn earworm, Heliothis zea (Boddie). The only significant control agent, fungal disease, acted too slowly to prevent economic damage by this insect.
Biology of immature Culicoides variipennis ssp. australis (Coq.) (Diptera:Ceratopogonidae) at Saltville, VA
Vaughan, Jefferson Archer (Virginia Polytechnic Institute and State University, 1985)
The larval and pupal biology of a unique population of gulicoides variipennis inhabiting the brine ponds of Saltville, VA was studied. Developmental threshold temperatures (OC) and thermal constants (Odays) for larvae and pupae were 9.6OC and 387Odays (larval stage) and 9.6OC and 3OOdays (pupal stage) respectively. Accumulated heat units recorded in the field ranged from 366—376Odays between successive generations in the summer. Heat accumulations required for completion of immature development of Q. variipennis were found to be much greater (83lOdays) for the overwintering generation. During the summer, larval/pupal distribution within the littoral zone of a brine pond was confined to the surface cm of mud at or near the shoreline. Insects overwintered farther offshore, mostly as 3rd instars. In ear1y' March, most larvae had xnolted to 4th instars and migrated above shoreline to pupate. Adult emergence occurred in April. Three summer generations were documented for 1983-1984 at Saltville._ Life tables and survivorship curves were calculated for the overwintering generation and the first summer generations for 1983 and 1984. For the overwintering generation, there was a relatively constant mortality rate between successive ageclasses (Type II survivorship curve). During the summer, there was relatively little mortality between successive larval age—classes but a dramatic increase in mortality was evident at the pupal stage (Type I survivorship curve). Late instar larvae were found to migrate from the shoreline onto the exposed mudflats to pupate, thus becoming vulnerable to predation by ants and carabid beetles. Excellent survival rates of the larvae during the summer was attributed to habitat stability, the paucity of predators and parasites and abundant microfloral content (i.e. food} of the pond water. Intra-specific competition for food resources appeared to be alleviated somewhat by partitioning of those resources on a diurnal cycle.
Bionomics of Platynota flavedana Clemens and P. idaeusalis (Walker)(Lepidoptera: Tortricidae) in Virginia apple orchards
David, Paul Joseph (Virginia Polytechnic Institute and State University, 1985)
The effects of pheromone trap placement on male moth catches of both species were studied. For P. flavedana, traps hung at 2.1 and 3.0 meters captured the greatest number of moths. Trap heights of 1.2, 2.1, and 3.0 meters caught the greatest number of P. idaeusalis moths. The outside-the-canopy trap position captured more P. flavedana moths, while the within-canopy trap location caught the greatest number of P. idaeusalis moths. Traps placed in the west portion of the tree captured the greatest number of P. flavedana moths. P. idaeusalis moth catches were not influenced by compass quadrants. Trap design and pheromone dispenser and rate influenced trap catches of P. flavedana. Development of P. flavedana and P. idaeusalis on a meridic diet was observed at constant temperatures in the laboratory. Lower developmental threshold values for egg, larval, and pupal stages of P. flavedana were: 10.6, 8.6, 9.0°C, respectively. Lower developmental threshold values of 9.7, 7.0, and 8.5°C were estimated for P. idaeusalis egg, larval, and pupal stages, respectively. An average of 101.5 °D_10.6’, 379.6 °D_8.6’, and 126.0 °D_9.0’ were required for development of egg, larval, and pupal stages of P. flavedana, respectively. P. idaeusalis required 104.7 °D_9.7’, 442.7 °D_7.0’, and 132.2 °D_8.5’ to complete development in the egg, larval, and pupal stages, respectively. Differences in rate of development were observed between food sources for both species. Within-tree spatial distribution of egg masses and fruit damage resulting from larval feeding for both species was investigated. P. flavedana egg masses were mostly found in the southern portion of the tree below 1.8 meters. Egg masses of P. idaeusalis were observed in greatest numbers in the southern and eastern quadrants of the tree below 2.8 meters. Fruit damage caused by larvae of both species was greatest in the lower portion of the tree. Wind dispersal of first-instar larvae between trees is believed to have influenced fruit damage distribution. The seasonal activity of P. flavedana and P. idaeusalis was monitored. Degree-day accumulations for first moth catch, first and peak egg deposition, and first and peak egg hatch of both generations are presented.
A biosystematic revision of the Nearctic species of the mayfly genus Isonychia (Ephemeroptera: oligoneuriidae)
Kondratieff, B. C. (Virginia Polytechnic Institute and State University, 1982)
The Nearctic species of the genus Isonychia Eaton are revised. Eighteen species are recognized, of which three are described as new; eleven species names are placed in synonymy. Isonychia campestris McDunough is recognized as a fully valid geographically restricted species. Two subgenera, Isonychia sensu stricto and Prionoides Kondratieff and Voshell are recognized on the basis of adult and nymphal characteristics. Isonychia s.s. includes four species groups: bicolor group with four species, arida group with one species, sicca group containing five species, and diversa group with one species. The subgenus Prionoides includes seven species. A Neotype is designated for l. arida (Say). Previously undescribed characters of the nymphal gills are described and illustrated. The male genitalia and eggs are illustrated for every species. The distribution of each species is mapped. Diagnostic keys to male adults and nymphs are presented. A discussion of the nomenclatural history of the genus and each species is included. Diagnostic characters, rearing and collecting techniques are also discussed. The life histories and life cycles of two populations of Isonychia (Isonychia) bicolor (Walker) and one population of Isonychia (Prionoides) obscura Traver are presented in detail. Many features used in the past as specific criteria, especially in the bicolor and sicca Groups are found to be related to developmental periods of given populations involving geography, elevation, water temperature and stream size. The life cycle of I. bicolor is probably bivoltine at both sites. At the trout stream site there is a large-sized spring emerging generation and a much smaller summer emerging generation with considerable overlap. Isonychia obscura Traver is univoltine with adult emergence in mid-June and with egg diapause during the summer months. Additional life history information is also presented for I. (l.) tusculanensis Berner and I. (P.) serrata Traver. The evolution of the genus Isonychia and the two subgenera l. (Isonychia) and I. (Prionoides) is hypothesized. The North American biogeography of Isonychia may have included an invasion of North America via the "asiamerican" land mass of the Cretaceous. The early Isonychia mayflies may have been adapted to low order cool streams of high elevations. This lineage was probably similar to the subgenus Prionoides. Isonychia s.s. has been successful in colonizing the upper and lower austral zones and appears to be a warm water adapted group.
Catabolic substrate utilization patterns: varying humidity and dietary regimens in the American cockroach Periplaneta americana (L.) (Dictyoptera: Blattidae)
Sherertz, Peter Chamness (Virginia Polytechnic Institute and State University, 1986)
Changes in metabolic substrate utilization patterns resulting from exposure to varying humidity and dietary regimens were examined in the adult, male American cockroach. A series of respirometric experiments were conducted to monitor changes in respiratory quotient (RQ), oxygen quotient (QO₂), food and water consumption and body weight. Also, a series of radiolabel experiments, utilizing injected ¹⁴C-glucose and ¹⁴C-palmitic acid, were conducted to determine radiolabel content (after exposure to varying humidity and dietary regimens) in whole body, feces, ¹⁴CO₂, hemolymph, fat body tissue and cuticle. The results of these two series of experiments were compared to determine the overall effects of humidity and diet on catabolic substrate utilization pattern changes in the American cockroach. In these experiments, variation in dietary regimens appeared to play a more significant role than humidity variations with respect to significant differences observed in insect RQ, QO₂, body weight and radiolabel incorporation in whole body, ¹⁴CO₂ , hemolymph, and fat body tissue. However, humidity significantly affected radiolabel incorporation in fat body tissue in the glucose experiments and ¹⁴CO₂ in the palmitic acid experiments. RQ and QO₂ data from the respirometric experiments and ¹⁴CO₂ data from the radiolabel experiments suggested that cockroaches deprived of food, but provided water to drink, change their metabolic substrate utilization pattern from initial catabolic substrates such as carbohydrates to lipid-based substrates. Also, cockroaches deprived of either water (FO) or food and water (OO) appeared to change metabolic substrate utilization patterns toward carbohydrates, but the final carbohydrate metabolic substrates are still unknown. Cockroaches provided water, but no food, showed a change from initial RQ values (low humidity OW = 0.92 and medium humidity OW = 0.86) to terminal RQ values (low humidity OW = 0.71 and medium humidity OW = 0.68) representative of lipid-based substrate metabolism. There was also an unexplained decrease in QO₂ (initial low humidity OW = 0.45 ul/mg/hr and terminal low humidity OW = 0.28 ul/mg/hr; initial medium humidity OW = 0.35 ul/mg/hr and terminal medium humidity OW = 0. 30 ul/mg/hr). Also, cockroaches deprived of water (FO) or food and water (OO) showed an overall experimental rise in RQ values (initial low humidity FO = 0.87; and terminal low humidity FO = 0.87; initial medium humidity FO = 0.82 and terminal medium humidity FO = 0.85: initial low humidity OO = 0.79 and terminal low humidity OO = 0.88; initial medium humidity OO = 0. 75 and terminal medium humidity OO = 0.87). In addition, these same insects showed an overall experimental increase in QO₂ (initial low humidity FO = 0. 34 ul/mg/hr and terminal low humidity FO = 0.43 ul/mg/hr; initial medium humidity FO = 0.45 ul/mg/hr and terminal medium humidity FO = 0.49 ul/mg/hr: initial low humidity OO = 0.37 ul/mg/hr and terminal low humidity OO = 0.53 ul/mg/hr; initial medium humidity OO = 0.32 ul/mg/hr and terminal medium humidity OO = 0.45 ul/mg/hr), and in the radiolabelled glucose study OO insects showed an almost complete cessation of ¹⁴CO₂ release at 2 days (d). Terminal body weights differed significantly among cockroaches provided with both food and water (controls = FW), only water (OW), only food (FO) and no food or water (OO). Insects deprived of either water (FO) or food and water (OO) had significantly lower terminal body weights than those insects provided either water or food and water. Whole body water content increased and dry weight decreased in insects provided only water to drink.
A contribution to the knowledge of the odonata
Carle, Frank Louis (Virginia Tech, 1982-06-16)
Theories concerning the origin of insect wings and flight are reviewed and a new scenario for their origin proposed. It is suggested that environmental conditions of the small stream were responsible for the evolution of insect flight, and that thermoregulation as well as respiration was important in the preadaptation of wings. The possibility that the five paired convex-concave vein systems each represented a dorsal-ventral blood channel is suggested. Odonate wing vein homology and nomenclatural systems, and phylogeny are reviewed. The process of vein loss is evaluated in the Palaeoptera and a new system of odonate wing vein homologies proposed. The odonate wing mechanism is analyzed and the heretofore overlooked discal nodus characterized. Reevaluation of the comparative morphology of fossil and recent Odonata indicates that Protozygoptera and Protanisoptera represent evolutionary side branches, that the Anisozygoptera is polyphyletic, and that Isophlebiidae and Calopterygoidea are the most generalized Odonata known. Previous scenarios explaining evolution of the unique odonate copulatory process are reviewed. Considering the copulatory behavior of the Calopterygoidea generalized supports evolutionary trends toward male domination and in-flight completion of the process. Assuming direct sperm transfer the original odonate mode requires that originally oviposition be in tandem and that sperm transfer to and from male anterior abdominal sterna be accidental. In contrast, assuming an original indirect transfer of sperm leads to a copulatory sequence similar to that of the Odonata. The proposed scenario differs from others in that extraordinary postures are not envisioned, the process is completed at rest, and the odonate tandem hold is developed prior to copulation. Anisopteran morphology and phylogeny are reviewed and reliable dentification keys developed for North American families and genera, and for 180 anisopteran species collected in Virginia and vicinity. Each species is described and photographed, including seven new species. The biogeography of Virginia Anisoptera is best explained by overlapping biotic regions, the fauna being a mixture of eastern North American, boreal, and tropical elements. New efficient methods for collecting, preserving, and rearing Odonata are described.
The ecology and management of the oriental cockroach Blatta orientalis L. (Orthoptera:Blattidae) in the urban environment
Thoms, Ellen Mary (Virginia Polytechnic Institute and State University, 1986)
The oriental cockroach, Blatta orientalis L., was found to be an important seasonal household pest. Of 151 residents interviewed in two Roanoke apartment complexes in Virginia, 90% had seen oriental cockroaches, 60% considered one oriental cockroach indoors to be a problem, and 77% had taken steps to control these cockroaches. Monitoring oriental cockroach populations indicated when and where treatment would be necessary to reduce cockroach infestations. The adult cockroach population peaked in late June and July, and declined through August and September while the number of nymphs increased. Eighty percent of all cockroaches trapped at Roanoke apartment buildings were caught at porches, the primary cockroach harborage sites. In a mark-recapture study at four apartment buildings, 50% of the resighted oriental cockroaches remained at one porch, 36% moved along one side of a building, 13% moved between the front and back of a building, and 2% moved between two buildings. Only 1-5% of the oriental cockroaches marked outdoors were ever captured indoors. One exterior perimeter and crawlspace application of encapsulated chlorpyrifos or diazinon in early June was the most effective insecticide treatment, reducing oriental cockroach populations by at least 85% for two months. Oriental cockroaches populations were reduced 78% and 50% two months after application of Dursban 4E (chlorpyrifos) and Combat bait trays (hydramethylnon), respectively. Structurally modifying buildings, to limit cockroach access to harborage in porch and wall voids, did not significantly (P < 0.05) reduce oriental cockroach populations, even one year after treatment. Structural modification was labor intensive, requiring at least eight times more man-hours per building compared to insecticide applications. The evaniid wasp Prosevania punctata (Brullé) had been seen in apartments by 60% of the Roanoke residents interviewed. This wasp parasitizes and destroys the oothecae of oriental cockroaches. P. punctata exhibited a maximum parasitization rate of 51% for oothecae of oriental cockroaches in laboratory conditions. Three peaks of evaniid wasp field populations closely followed the rise, peak, and decline of adult oriental cockroach populations. A resident education program significantly (P < 0.05) reduced the percentage of residents in Roanoke apartment complexes who thought evaniid wasps were a problem or killed them. However, evaniid wasps parasitized only 15% of the field collected oriental cockroach oothecae, significantly fewer (P < 0.05) than the 36% parasitized by the eulophid wasp Tetrastich us hagenowii. In addition, 60% of the residents still killed evaniid wasps, despite the education program.
Effects of an insecticide on German cockroach behavior
Bret, Brian Louis (Virginia Tech, 1985-05-03)
A quantitative and qualitative study of the behavioral effects of an insecticide on various life stages of the German cockroach, Blattella germanica (L.), was conducted. Comparisons between a susceptible laboratory strain (VPI) and a resistant field strain (BP) were made to examine the relationship between physiological resistance and behavioral resistance. The effects of vapors from a formulation of 1% propoxur in oil were compared with vapors from a mineral oil control. Vapors from the control had little effect on cockroach behavior. Adult males, adult females, and middle instars were repelled from aquaria containing the insecticide vapors. Early instars sought shelter in the pores of water sponges. No differences in behavior due to reproductive state were observed as females with oothecae and females without oothecae were equally repelled. Responses by adult males included increased movement, antennal grooming, and tarsal grooming. Electroantennogram studies showed that the vapors of the propoxur formulation were detected by the antennae. Adults of the susceptible VPI strain responded more strongly to the insecticide vapors, relative to the controls, than did adults of the resistant BP strain. The negative correlation between physiological resistance and behavioral responses was not due to the development of behavioral resistance. Rather the resistance mechanism of the BP strain was probably responsible for inhibiting the behavioral response of that strain. Responses to the propoxur insecticide may have been compounded by solvents in the formulation, but differences between the two strains were probably due to the propoxur. The oil base had no effect on cockroach behavior. That wet sponges provided safe harborage for the early instars indicates the importance of even short range dispersal. Also, the use of repellent barriers to exclude cockroaches from sensitive areas may become less effective if physiological resistance in cockroach populations is accompanied by decreased avoidance responses. Knowledge of the levels of physiological resistance must be supplemented by an understanding of the behavioral characteristics of insect populations for the successful development of pest control programs.
Effects of low intensity magnetic fields on cabbage loopers
Daugherty, William Duane (Virginia Tech, 1974-05-05)
Possible effects of steady low strength magnetic fields on insects were studied using the cabbage looper moth, Trichoplusia ni (Hubner). In the first tests, adult loopers were used to determine their locational preference in response to areas of stronger or weaker magnetic field ranging from slightly above the geomagnetic field strength to a strength of 120 gauss. In a second series of tests, looper eggs were continuously exposed to steady magnetic fields of various strengths ranging from 10 to 1850 gauss. In a third series of tests t individual adult loopers were exposed to a steady 500 gauss field for five minutes. Oxygen consumption was monitored to indicate the level of moth activity before, during, and after this exposure. Results of the tests conducted revealed no effect of low magnetic fields on moth locational preference, egg hatchability, or activity level.
Evaluation of the potential of Pteromalus puparum (L.) (Hymenoptera: Pteromalidae) for suppression of the imported cabbageworm and parasitism of the diamondback moth
Lasota, Joan Ann (Virginia Polytechnic Institute and State University, 1985)
The seasonal abundance of the imported cabbageworm, Artogeia rapae (L.)), cabbage looper Trichoplusia ni (Hubner)) and diamondback moth (Plutella xylostella (L.)) was determined in 1982 to 1984 on cabbage in southwest Virginia. The imported cabbageworm was the most important pest. It had one and a partial second generation in 1982 and 1983, and two and a partial third generation in 1984. Market Prize and Green Winter varieties had lower A. rapae infestations than Abbott & Cobb #5 or Rio Verde. Two generations of the diamondback moth, which preferentially fed on cabbage leaves versus heads, were seen in 1983 and 1984. Diadegma insularis (Meus.) (Hymenoptera: Ichneumonidae) parasitized 46% and 69% of the diamondback moth in 1983 and 1984, respectively. Higher parasitization of P. xylostella was found in pupae collected from Abbott & Cobb #5. Two generations of the cabbage looper were seen in 1983 and a single generation in 1984. Pteromalus puparum (L.) (Hymenoptera: Pteromalidae) parasitized 64.1% and 32.5% of imported cabbageworm pupae in 1983 and 1984; parasitism was most pronounced in the latter part of the season. High percentages of parasites successfully emerged as adults, indicating efficient host utilization. Most parasite mortality within the host occurred in the larval stage; mean adult parasite emergence per host for 1983 and 1984 was 52.3 with a 1:1 sex ratio. P. puparum parasitized either host sex, producing equal proportions of male and female parasites. Adult female P. puparum were not adversely affected by residues of methomyl (Lannate®), permethrin (Pounce®) and fenvalarate (Pydrin®), but males showed significantly higher mortality than controls following exposure to methomyl after 12 h, and methomyl and permethrin after six days. adults were successfully refrigerated for up to 15 days at 3°C in individual gelatin capsules. Survival beyond 15 days was better at l5°C and 23°C. A. rapae larvae could be reared at densities of 30 to 60 larvae per 70±10 g on a high wheat germ artificial diet. Pupae from the lowest density were larger in length and weight than those reared at the two higher densities, and all laboratory-reared pupae were smaller than either normal or parasitized field pupae.
The evolution and ecological genetics of pupal color dimorphism in swallowtail butterflies (Lepidoptera: Papilioninae)
Hazel, Wade Nelson (Virginia Tech, 1980-06-05)
Data bearing on the evolution, environmental control and genetic basis of pupal color dimorphism was presented or discussed for six species of swallowtail betterflies. Papilla glauces and P. cresphontes produce only brown pupae while P. polyxenes, P. troilus, Battus philenor and Eurytides marcellus produce both green and brown pupae. Natural pupation sites of the species were located and results were generally consistent with the hypothesis of Sheppard (1958) which relates the evolution of the environmentally-cued dimorphism to environmental variation. The relative importance of texture, color and photo-period as environmental cues controlling the expression of pupal color was investigated and the results were discussed in relation to differences in the pupation sites of the species. The genetic basis of pupal color was investigated in E. marcellus by selecting for an increase in the tendency of larvae to produce green or brown pupae. The results were found to be consistent with the genetic basis of the trait as proposed by Hazel (1977). It was concluded that the primary factor responsible for the evolution of the dimorphism and the environmental cues which control its expression is nature of the pupation sites that a species utilizes.
Fine structure of the ovipositor and studies of feeding and oviposition site selection by the serpentine leafminer, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)
Knodel-Montz, Janet Jean (Virginia Tech, 1983-12-05)
Ovipositors of female leafminers were examined microscopically to locate and describe types of sensory receptors present. Two basic types were found: trichoid sensilla and basiconic sensilla. These receptors are believed to function as mechano- and chemoreceptors to evaluate the suitability of a host plant for feeding, oviposition, and subsequent larval development. Two greenhouse experiments were conducted to evaluate the effects of photoperiod and application of plant growth regulators on two factors: 1) feeding and oviposition site selection and 2) spatial distribution of feeding and oviposition sites on individual chrysanthemum plants. In the photoperiod experiment, leafminers fed and oviposited more intensely on chrysanthemums grown under short days (SD) than on plants grown under long days (LD). Densities of feeding punctures and larval mines on chrysanthemums grown under SD was positively related to leaf height on the plant, and negatively related to leaf trichome density. Spatial distribution of feeding and oviposition sites within plants under LD was variable, and no specific pattern of preference was discerned. An experiment to determine the effect of plant growth regulators on site selection by female leafminers revealed no significant differences (P > 0.05) in feeding and oviposition densities on chrysanthemums treated with plant growth regulators napthalene napthaleneacetic acid, gibberellic acid, and daminozide.
Group formation and dispersal in the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae)
Bret, Brian Louis (Virginia Tech, 1982-08-12)
The studies presented here are an effort toward learning about the behavior of small mixed populations of German cockroaches. Of particular interest was the effect of female cockroaches on the behavior of the group, particularly the group formation within a harborage and the dispersal from a harborage. The effect of females was looked at with respect to female density and reproductive state. Populations aggregated at low female densities. This response increased when densities of gravid females increased but decreased when densities of non-gravid females increased. The effects of female reproductive state on dispersal could not be determined as non-gravid females developed egg cases by the end of the study. Increased female density caused increased dispersal of females and mid-instars. The mid-instars were the primary dispersers in each experiment. Early instars, excluding escapees, dispersed least. The results of these studies indicate the females of a population can mediate the behavior of that population and its members. It is postulated that this may be achieved by the production and/or regulation of sex, aggregation, and dispersal-inducing pheromones by females.
Influence of flight activity and octopamine on hemolymph trehalose titers in Heliothis zea (Boddie) (Lepidoptera: Noctuidae)
Davidson, Deborah Ann (Virginia Tech, 1990-04-05)
Hemolymph trehalose concentrations of male and female Heliothis zea were quantitated by high performance thin-layer chromatography (HPTLC) at various ages and times of the day and related to flight activity. Effects of octopamine injection or stress on trehalose levels were also quantified. Flight activity was measured with a 32-channel computerized actograph that simulated sunrise at 0300 EST (Eastern Standard Time) and sunset at 1700. Males exhibited greater flight activity than females at all ages examined. Flight began near sunset, continuing through the night and ending around sunrise. Females flew continuously throughout the night, whereas males exhibited two peaks in activity: the first between 1700 and 1900, followed by a second peak between 2000 and 2400. Flight activity peaked on days 3-4 in males and days 4- 5 in females. Trehalose was the predominant hemolymph sugar, comprising 82-100% of total hemolymph sugars. Glucose was the second most frequently observed sugar. Trehalose concentrations were variable, ranging from < 1 ug/ul to 37 ug/ul. Lab-reared moths had higher and more variable trehalose concentrations than field collected (wild) moths. Trehalose levels were relatively constant several days after emergence in both sexes but decreased significantly by day 6 in males. When examined over a 24 hour period, trehalose concentrations gradually increased throughout the day in day 4 males and females, peaking one hour before sunset at approximately 18 ug/ul. This peak is hypothesized to be related to flight preparation. Females showed a second peak in trehalose levels at 1800, but males’ trehalose levels continued to decline until 1900. Males and females exhibited more similar patterns in trehalose concentrations when sampled every 15 minutes over the sunset period (1500-1900) than when sampled at hour intervals. Injections of octopamine, reputed to induce hyperglycemia in other insects, failed to elicit significant increases in trehalose levels in either fed or starved moths. Starved moths had lower trehalose concentrations than fed moths. Method of analysis (HPLC, HPTLC and anthrone) produced no differences in measured levels of trehalose or glucose. Various forms of stress (handling, shaking), also reported to induce hyperglycemia in other insects, similarly did not significantly increase trehalose titers in moths.
Investigations of the destructive behavior, and method for control of the lesser mealworm, Alphitobius diaperinus (Panzer), (Coleoptera: Tenebrionidae)
Despins, Joseph L. (Virginia Polytechnic Institute and State University, 1986)
The relationship between the types of construction of high rise caged layer houses and insulation damage produced by the lesser mealworm was examined. Polyurethane insulation which had heavy-weight paper glued to its surface and was installed with tape to seal off the seam between the insulation boards had no infestations. Structures with concrete block pit walls had lower insulation infestations than those houses with wooden walls forming the pits. Houses with a support structure set on top of the concrete block pit wall had lower infestations than houses built with the support structure set directly into the earth. The insulation installed nearest the pit was the most severely infested, and infestation intensity was inversely proportional to insulation height above the manure pit. Damage in extruded polystyrene insulation resulted in a substantial loss of volume of material in the corner areas of the insulation panels, and caused a significant reduction in insulating quality. Observations were made on the effect of manure moisture and poultry house construction materials on lesser mealworm dispersal behavior. Larvae and adults preferred manure habitats of 30 and 40% moisture, and dispersal from the manure significantly increased when manure moisture was increased to levels of 50 and 60%. Larvae climbed a significantly greater distance up a vertical wooden surface than up a vertical concrete block surface under field conditions. Results indicate that structures built with wood pit walls are predisposed to infestations, and that fluctuating manure moisture levels in these houses can indirectly contribute to accelerated infestation by driving the larvae from the manure pits into the insulation. Insecticide sprays, plastic films, paint barriers applied to the surface of extruded polystyrene, and different types of insulation were evaluated for lesser mealworm resistance. In a laboratory study, tetrachlorvinphos and pirimiphos-methyl sprayed on extruded polystyrene produced greater than 90% mortality in larval and adult populations up to 71 weeks postapplication. Larvae were unable to penetrate either chlorpyrifos-impregnated or non-insecticidal polyethylene films. Infestation intensity was inversely proportional to insulation cell size. Effective treatments identified under field conditions were permethrin and pirimiphos-methyl sprays, and two formulations of chlorpyrifos-impregnated latex paint. Insulation materials with a cell size of 1.5 mm were resistant to lesser mealworm field populations.
Life history studies of the old house borer, Hylotrupes bajulus (L.) (Coleoptera: Cerambycidae)
Cannon, Kevin Francis (Virginia Tech, 1982-03-05)
A North American biotype of the old house borer, Hylotrupes bajulus (L.) was established from field and laboratory data. This biotype is based on differences in size and longevity of the life stages and on adult fecundity. N. A. females were observed to oviposit a mean of 165.1 ± 15.5 eggs in comparison to 119.4 (South African) and 105.2 (European). Oviposition period was 5.2 ± 0.5 days for the N. A. biotype and 3.9 and 12 days for the South African and European, respectively. Eggs of the N. A. biotype were smaller than those of the South African and incubation period (8.5 ± 0.3) shorter than both South African (14.0) and European (9-12). Development and comparisons of the pupal and larval stages are presented and discussed. Comparisons of the N. A. and European biotypes under similar temperature, humidity and nutritional conditions found no significant differences between biotypes. These results indicate that the biotypes have undergone little genetic change since their separation over 200 years ago. The old house borer is quite responsive to environmental conditions and the biological variation noted in field populations is attributed to non-genetic modifications of the phenotype. The high degree of biological flexibility noted in this species allows the OHB to inhabit marginal habitats and explains its present world-wide distribution. The OHB was successfully reared from egg to adult in 9-11 months on an artificial diet. An oligidic diet was developed and was composed of ground host tissue (southern yellow pine, Pinus spp.), purified cellulose, agar, and basic nutrients. This diet provided an adequate physical and nutritional environment as noted in the reduction in larval mortality and developmental period when compared to conventional rearing methods. Comparative nutritional, physiological and behavioral studies are now possible between larvae feeding on artificial diets and conventional wooden blocks. Observations of the adult mating behavior, fecundity, oviposition period and egg viability were reported under two mating regimes: single and multiple. Fecundity and egg viability were not significantly different between regimes. However, the number of egg batches, length of oviposition period and the longevity of adult females were significantly different. Adult behavior between regimes was not noticeably different. Males actively compete for females when other males are present and aggressive interactions are common. The practical and evolutionary significance of single and multiple matings is discussed. Consumption, growth, utilization and respiration by three weight classes of old house borer larvae, under 5 constant temperatures and relative humidity were studied. Wood consumption in all larval weight classes was greatest in the temperature range of 20° to 30°C and significantly reduced below and above these temperatures. Growth rates for small larvae were not significantly different among temperatures. Medium and large larvae recorded negative growth rates at 15° and 35°C. Wood utilization was greatest at temperatures of 20° and 25°C. Respiration rates were highest for small larvae. Small larvae were apparently more efficient at converting wood ingested to biomass at all temperatures.
Megacerus discoidus, a potential biological control agent of hedge bindweed in southwestern Virginia
Wang, Ren (Virginia Polytechnic Institute and State University, 1985)
Megacerus discoidus (Say)(Coleoptera: Bruchidae), a native North American seedfeeder, has 4 larval instars and one generation a year. Overwintering occurred in the 4th instar. Larvae fed on 40-50% of the seed content before diapause and the rest of the seed in the following spring. When more than one larvae attacked a seed, only one adult emerged because of cannibalism, which was most common among 2nd and 3rd instars. Adults oviposited mainly under the bracts of host seedpods. The life cycle of the beetle was well synchronized with the host phenology. When diapause of the insect was experimentally terminated under 20°C and 28°C, there was increased mortality and prolonged adult emergence. No adult emergence occurred when infested seeds were maintained in the dark under 10°C for 200 days. However, mortality of the larvae was significantly increased. Humidity and soil coverage of host seeds had no significant impact on the beetle mortality during diapause under field conditions. Of 19 plant species tested, only hedge bindweed and wild sweet potato, Ipomoea pandurata, supported larval development to adults. Oviposition occurred only on seedpods of hedge bindweed and heavenly blue morningglory, Ipomoea tricolor. The latter did not support larval development. An infestation rate of 5 M. discoidus eggs per seedpod of hedge bindweed in the field cages was achieved by releasing the adults at a relatively high adult/plant ratio (1.2 pairs/plant) plus inoculation of eggs on all seedpods in the cages. This resulted in a high rate (ca. 70%) of seed infestation, but did not destroy all of the seeds in the field cages. Release of lower number of adults led to lower seed infestation. Seed consumption did not cause any change in reproduction and vegetative growth of hedge bindweed. I consider the use of M. discoidus to be safe but it must be combined with other stress factors to achieve effective control.

Browsing by Author "Eaton, John L."

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