Movement Behavior of the Pine Needle Gall Midge (Diptera: Cecidomyiidae)

The movement behavior of the pine needle gall midge (Thecodiplosis japonensis Uchida Et Inouye (Diptera: Cecidomyiidae)), an invasive species in China, was determined by using a tethered flight technique and digital videography in the laboratory. The flight distance, duration, and speed of females were compared at different ages (2–10 h) and ambient temperatures (17, 21, 26, and 30°C). Female flight distance and duration at 26°C were significantly greater than those at 17°C and 21°C. The age of T. japonensis did not significantly affect the three flight characteristics. For females at 2–10 h of age at 26°C and 70% RH, the maximum flight distance was 667.59 m; the longest flight time was 6,222.34 s; and the fastest flight speed was 0.44 m·s−1. For larvae wetted with water, the highest jump was 5.7 cm; the longest jump was 9.6 cm; and the greatest distance moved in 5 min was 27.13 cm, which showed that the active dispersal potential of larvae was very low.

Structural dynamics in the host-parasitoid system of the pine needle gall midge (Thecodiplosis japonensis) during invasion

The structural dynamics of host–parasitoid populations play a key role in the mechanism of natural community development with invasive species. Species invading new habitats experience coevolution with their newly acquired natural enemies, and their population dynamics are driven by a complex interaction between biological and environmental factors. We examined the biological and environmental factors which potentially influence a community of parasitoids throughout the 25-year invasion history of the pine needle gall midge (PNGM), Thecodiplosis japonensis, an important pest of pines in eastern Asia. We found that differences in establishment sequence and competitive ability among the parasitoids attacking this species determined the parasitoid community’s structure and dynamics. In particular, the timing for the initial establishment of the host–parasitoid association, incomplete superiority in competition among parasitoids, and indirect competition by a combination of the parasitoids were important factors for determining community’s structure and dynamics. Finally, the history of change in the community composition could be explained by the phenology differences in its member species, mediated by environmental factors.