Feeding and associated behaviour of the adult cabbage root fly Erioischia brassicae (Bch.) (Dipt, Anthomyiidae) under laboratory conditions

Abstract

AbstractAdults of the cabbage root fly (Erioischia brassicae (Bch.)) reared in culture were inactive on the day of emergence but they fed on carbohydrate (sucrose) and protein (Yeastrel) on day 2. Without food, the egg follicles increased to approximately one-third of their maximum size and were then resorbed. When food was available, females ingested sucrose on days 2 and 3 to mature the first batch of eggs, without any stimulus from mating. Without either a mate or a suitable oviposition site, females retained most of their eggs. Females obtained sufficient food for egg maturation by day 4, when their egg follicles were 400 μm, approximately half the size of the mature eggs. Only females mating on day 4 laid eggs at the expected time 6±0·3 days after emergence. With a suitable oviposition site, these females laid 299±48 eggs, approximately twice as many as any other females, and ten times as many viable eggs. When males were not allowed to mate, peak ingestion was delayed from days 8–12 to days 14–18. Mated females provided with an oviposition site laid most eggs on days 5 and 6 and fed again on day 7. This second peak of feeding was delayed until day 9 when mated females were denied, or unmated females were given, an oviposition site. Similar volumes of sucrose were imbibed by females whether they laid or retained their eggs. Females denied both a mate and a suitable oviposition site laid less than 1% of the expected eggs.