Biology and Host-Range Testing of Laricobius kangdingensis sp. n. (Coleoptera: Derodontidae), a Newly Discovered Predator of Hemlock Woolly Adelgid, Adelges tsugae Annand (Homoptera: Adelgidae)
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Developmental rates were studied in fall 2003 and spring 2004. Combined with data gathered previously at 12 and 15ÂºC in early 2003, the 6, 9, and 18ÂºC data were used to determine lower temperature development thresholds for the egg (2.8ÂºC), larval (1.6ÂºC), and pre-pupal (5.8ÂºC) stages. The egg and larval thresholds are lower than those observed for L. nigrinus. Laricobius kangdingensis sp. n. individuals completed development only at 12 and 15ÂºC; however, these adults did not emerge from aestivation after pupation.
Laricobius kangdingensis sp. n. appears to be host-specific. In paired-choice feeding tests, adults consumed significantly more HWA than two other adelgid species [eastern spruce gall adelgid, Adelges abietis (L.), and pine bark adelgid, Pineus strobi (Hartig)], the pine needle scale, Chionaspis pinifoliae (Fitch), and the woolly alder aphid, Paraprociphilus tessellatus (Fitch). In paired-choice oviposition tests, females laid more eggs on HWA-infested eastern hemlock than on any other test prey. In no-choice host suitability experiments larvae fed on HWA; eastern spruce gall adelgid; the larch adelgid, A. laricis Vallot; the balsam woolly adelgid, A. piceae (Ratzeburg); pine bark adelgid; and pine needle scale, but not on woolly alder aphid or elongate hemlock scale, Fiorinia externa Ferris. Although no larvae completed development in any of the bioassays, 6 out of 15 larvae (40%) in the HWA treatment reached the pre-pupal stage. One larva out of 6 reached the pre-pupal stage on pine bark adelgid.
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