Differences In The Susceptibility Of Aquilaria Sinensis To Heortia Vitessoides (Lepidoptera:Crambidae) And The Effect Of Substrate On Pupation Site Choice

Aquilaria sinensis(Lour.) is an endangered tree species in china. It can be made into medicine and is used in perfume industry. Heortia vitessoides Moor is an important defoliator and often causes complete defoliation of A. sinensis. I investigated the damage patterns of A. sinensis forests. The survey found there are significant differences in the leaf morphology of A. sinensis. Significant differences in the extent of the damage by H. vitessoides existed in the same A. sinensis forest. I collected 24 kinds of leaves with different morphological characteristics from two A. sinensis forests. Their leaf length, width, thickness, leaf fresh weight and leaf dry weight were measured in the laboratory. I conducted choice tests using 2-3 instars H. larvae to study the preference of different leaves. Two A. sinensis plants which were not favored by H. vitessoides were identified.It was observed that most of the larvae aggregate during feeding. In the 21 dual-choice tests, they usually aggregated on one A. sinensis leaf. The results partially explain why some tree leaves were seriously damaged greatly and some tree leaves were intact.To help understand humidity requirements of H. vitessoides pupae, four different substrates were tested: the natural sand, the sandy loam A, the sandy loam B and the silt loam. They are different in sand, mud, clay, and organic material content and PH. The sand content and PH are highest in “natural sand”. Sandy loam A and sandy loam B are similar. The mud content in silt loam is the highest. Six humidity(0, 20, 40, 60, 80 and 100%) of each substrate were prepared. The H. vitessoides larvae were offered each type of substrate at six humidity. Results show significantly lower number of H. vitessoides chose to pupate in substrate with 0, 80 and 100% humidity. Most preferred were 20% to 60% humidity. In the sand, sandy loam A, and sandy loam B, the survival and pupation of H. vitessoides were highest in 20% and 40% humidity substrate. In silt loam, H. vitessoides larvae were mostly concentrated in 40% and 60% humidity substrate.