Influence Of Photoperiod And Food On The Growth, Development And Reproduction Diapause Of Harmonia Axyridis (Pallas)

Harmonia axyridis (Pallas) (Coleoptera:Coccinellidae), native to a large part of Asia, is an important predatory lady beetle as natural enemie attacking agricultural and forestry pests such as aphids, scale insects, whiteflies, spider mites and so far. At present, H. axyridis is already imported to many other major agricultural regions as an efficacious biological control agent. Through the test, at 20℃combined with thirteen treatments of photoperiod (DD, 2L:22D, 4L:20D, 6L:18D, 8L:16D, 10L:14D, 12L:12D, 14L:10D, 16L:8D, 18L:6D, 20L:4D, 22L:2D, LL), the influence of photoperiod on the growth and development of pre-imagine, pre-oviposition time, percentage of oviposition, percentage of diapause, critical photoperiod and sensitive stage of the lady beetle were analysised. The results were as follows:Photoperiod had significant influence on the growth and development of H. axyridis. The duration time on the larval stage at the long photoperiod (light hours≥14h) was significantly prolonged, and short photoperiod (2h<light hours<10h) duration time significantly shortened, the light cycle of DD, 12L:12D under conditions of H. axyridis developmental duration in a transition period. Egg hatching needed more than 4d, and under the conditions of short photoperiod (light hours between 0h and 10h) egg development was more fast; larval stage under the long photoperiod (light hours>14h) conditions, development was significantly shorter (light hours between 0h and 10h) slow; the duration of pupal stage in general was 7.1d-7.5d.Photoperiod had significant influence on the fecundity of H. axyridis, incuding inflences on the pre-oviposition period, egg number of oviposition, ovarian development and development of fat body. Under different photoperiodic conditions, spawning period in the photoperiod of 16L:8D was15.8d, mean pre-oviposition period was within 15.3d under other photoperiod, and most females did not lay egg within 30d in the photoperiod of 10L:14D. After emergence of 30d, the development of H. axyridis between photoperiodic of the photoperiod 2L:22D and 12L:12D were remarkablely lower than those between 14L:10D and DD. The ovarian development of H. axyridis under the long photoperiod (light hours>14h) level to IV, V level mostly, under the light cycle of 10L:14D, diapause rate was the highest and the ovarian of H. axyridis were mostly belong to I, II level; change of the first egg chamber longitudinal length of the fastest ovariole had had the same trend with other parameters. Under conditions of the light cycle of 10L:14D, the diapause rate of H. axyridis was up to 96.1%, in the light cycle of 0h-10h, diapause rate raised with the illumination hours increased. Under ecological light period, H. axyridis showed the typical short photoperiod diapause development type, and the diapause critical photoperiod of H. axyridis at 20℃was 11.9L:8.1D. Studying on the invarious states, different day of the adult for sensitivity of H. axyridis, then that showed the adult state was the photoperiodic sensitive stage, and after eclosion of adult 1d-4d was the most sensitive age of feeling photoperiodic response; 1st-4th instar larvae and pupae developmental stage were also existing certain sensitivity to short photoperiod, and existing effected accumulation.on the diapause of H. axyridis producing.Under the diapause photoperiodic conditions when fed with Chaitophorus populeti (Panzer), Lipaphis erysimi Kaltenbach respectively, the diapause rateof H. axyridis fed on L. erysimi Kaltenbach was significantly higher than that of fed on C. populeti, but there were no significant differences on the duration time of pre-imagine, survival rate, emergence rate, sex ratio, ovarian development.The water content of diapaused H. axyridis was much lower than that of non-diapause ladybird beetle and the ovarian development level was lower, basically no yolk deposition. The longitudinal length of the first egg chamber of fastest ovariole was 16um. H. axyridis under diapause conditions laid eggs occasionally, but the amount of eggs was very low. PAGE electrophoresis reflected the blood protein in diapaused H. axyridis were quite different with those in non-diapaused.