LIFE HISTORY AND BIOLOGY OF EINFELDIA SYNCHRONA (DIPTERA: CHIRONOMIDAE)

Abstract

Einfeldia synchrona Oliver is univoltine in a small, shallow, highly eutrophic pond near Ottawa (45°N.). Adult emergence is synchronized with slight protandry in May, and from this small pond exceeded 145,000 individuals in 1970. Emergence is inhibited experimentally at short photoperiods. More than one egg mass is produced, during a period of several days following emergence. First instar larvae, which lack ventral tubules, are at first pelagic but build cases before moulting. The remaining three larval instars possess 1 pair of ventral tubules. Larvae show a preference for central areas of the pond over 40 cm deep, and show some mobility in response to seasonal depth changes. There are arrests in the development of larvae both in winter and during summer, with cessation of feeding, penetration into the mud, and construction in winter of special sealed cocoons. Marked year to year differences in the stage reached by winter, and in the larval population level, were detected. Many of these biological features are probably widespread in Chironomini and hence of some importance in the interpretation of studies of the bottom fauna.