The Study On Biological Characteristics Of Mycodiplosis Sp.

Mycodiplosis sp. belongs to Cecidomyiidae of Diptera. It is an enemy insect which feeds on the uredium of poplar leaf rust Melampsora larici-populina Kleb., so it has a potential value for controlling the pathogen prevalence. In this paper we studied the morphology, biological characteristics, larvae spatial distribution pattern, the effect of temperature on pupae development period and adult longevity of Mycodiplosis sp. using field investigation and lab breeding, and the research results will play an important role to further study the ecology, behavior, genetic and utility for biological control of Mycodiplosis sp..1. Morphological characteristics of Mycodiplosis sp.(1) Egg: Egg is oval, the length is 0.2-0.3 mm and width is 0.09-0.1 mm, the surface of egg is smooth and transparent. Egg dorsal is slightly uplift like arc, and ventral is straight.(2) Larva: Apodous larvae are fusiform, and the head retracted into prothorax. The results after scanning the larval body surface showed that it was very special and covered with the ossification slice like fish scale, the size and density of them is different in different parts of larval body. The prothorax, mesothorax and metathorax are all smooth film, there was one special"M"shape in prothorax venter. Serrated ossification slice of abdomen venter were sharp, long and backward, instead of pleopod. Four types of sensillums were found on the larval body surface, they are Sensillum baisconicum, Sensillum coeleoconica, Sensillum campaniform, and special Sensillum umbrella-shape located at the both sides of abdomen separately. The Sensillum umbrella-shape has not reported in other insects and its function was unknown.(3) Pupa: The pupa is exarate pupa, and the body color changed from pale yellow to russet, it has distinguished into four developmental stages such as prepupa, initial stage pupa, medium stage pupa and late stage pupa. Each segment has serrated ossification slice that evenly and backward, there is a pair of antennae and sensillum located at pupa head.(4) Adult: The length of female adults are about 1.25-1.5 mm, male adults are about 0.9-1.1 mm, and all of them covered with with densely tomentum. The moniliform antenna has 2+12 sections. Four types of sensillums were found on the antenna, and they are Sensillum micro-villus, Sensillum uncinus, Sensillum circumfila and Sensillum rattan-like. 2. Biological characteristics of Mycodiplosis sp.Mycodiplosis sp. can occur several generations one year, and has generation overlapping. It overwinters with last instar larvae in soil. Adults emergence from the soil in Apirl of next year and can last until June, the peak of emergence period is in the middle of May. The peak time of larvae is from mid August to late September, has a close phenology connection with the occurence of Melampsora larici-populina Kleb.. In mid November almost all larvae go into soil for overwintering. The adults have two peak emergence period such as 07:00-09:00 and 17:00-19:00 each day, adults can live about 2-3 days, while the last instar larva also have two peak pupation of 09:00-11:00 and 15:00-17:00.3. Temperature effect for pupae developmental and adults lifeThe developing period of pupae and adults life of Mycodiplosis sp. were studied under the five constant temperature (18℃, 22℃, 26℃, 30℃, 34℃) , analyzing the developmental threshold temperature and effective accumulative temperature of pupae. The results showed that the development period of pupae and adults life was reduced from 11.23d and 5.58d in 18℃to 5.98d and 2.98d in 30℃, and was negatively related with temperature, while the temperature had a significant influence on the developing period of its pupae and adults life(P<0.05). The development period of pupae and adults it extended a few and the developing speed became slow in 34℃. The developmental threshold temperature of pupae was 5.82±2.28℃, and the effective accumulative temperature was 142.03±17.52 day/degree.4. Space distribution of the larvaeThe larvae spatial distrbution pattern of Mycodiplosis sp. showed that Mycodiplosis sp. larvae had an aggregated distribution, this may be due to environmental heterogeneity, innate spawning behavior and aggregated behavior. A theoretical sampling model was developed by Iwao regression is N=1/D2(3.86/m+0.73).