Fine structure of the ovipositor and studies of feeding and oviposition site selection by the serpentine leafminer, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)

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.