Vol. 38 No. 4, 1999

Life History Studies of the Flightless Marine Midges Pontomyia spp.(Diptera: Chironomidae)

Keryea Soong*, Guo-Fang Chen and Jun-Ren Cao

Institute of Marine Biology, National Sun Yat-sen University, Kaohsiung, Taiwan 804

Keryea Soong, Guo-Fang Chen and Jun-Ren Cao (1999) The emergence of the marine midges, Pontomyia natans and P. oceana, was investigated in southern Taiwan in 1992 and 1996. P. oceana emerged after sunset and only on evenings near the new moon or the full moon, whereas P. natans emerged near dusk on every collection day. The mean emergence time of P. oceana varied by more than 3 h, being earlier in summer than in winter. The overlap in emergence times of the 2 species thus depended upon the season. Light conditions, i.e., the time of sunrise and sunset may be the proximate factors controlling emergence in P. oceana. Limiting emerging dates and times of P. oceana may be an adaptation for controlling the adults to lay eggs only during low tides at night. The tide, however, does not cue the diurnal emergence of the midges. Fertilized eggs of P. oceana were collected in the field for study in the laboratory. Larvae hatched in about 4 d at 25 °C, and 4 instars were necessary before the final emergence. The generation time was around 30 d. Males emerged about 1 h earlier than females. Since an adult remained active for only about 2 h, peak occurrence of males was found to coincide with peak eclosion of females. Moreover, the presence of males was important for the successful eclosion of females from their pupae, as demonstrated in the laboratory.

Key words: I.

*Correspondence: