Alewives Alosa pseudoharengus preyed upon larval yellow perch Perca flavescens during late April and early May in a Lake Ontario embayment. Based on stomach analyses of 1,308 alewives collected during the springs of 1984–1986, predation on larval yellow perch occurred primarily at night in littoral areas during the 2 weeks immediately following peak hatch of yellow perch. Among stomachs of all alewives caught at night in littoral areas, 30% in 1985 (N = 43) and 41% in 1986 (N = 71) contained yellow perch larvae. Mean numbers of whole larvae per alewife stomach were 3.8 in 1985 and 32.6 in 1986. As many as 361 intact larval yellow perch were found in one stomach. Mean total lengths of yellow perch consumed on two dates in mid‐May 1986 were 7.3 and 7.6 mm, compared to mean sizes of 8.0 and 8.6 mm of larvae living within the bay. We suggest predation by alewives on yellow perch larvae may reduce yellow perch recruitment in Lake Ontario as well as in other Great Lakes.

Copulatory responses to a variety of decoy objects baited with synthetic 15,19,23-trimethylheptatriacontane were induced in adult male Glossina morsitans morsitans Westw., provided the object was of similar shape and size to a female fly. Chemical and configurational (shape and texture) stimuli were important in eliciting and maintaining copulatory behaviour of males. A dose/response relationship was obtained from 7-day-old test males, with an EDg5 of 2 p g using as decoys solvent-washed dead males baited with 15,19,23-trimethylheptatriacontane. The quantity of this compound in 5-day-old adult females is more than 4.0 pg; in males, only 0.6 pg. It is considered to have the characteristics of a true contact sex pheromone for the species, and does not act synergistically with other less stimulatory synthetic compounds. Gas chromatographic analysis of adult female cuticular paraffins of G.m.morsitans showed the presence of two large peaks between C3, and C38 which were virtually absent in males. Young adults of both sexes possessed a series of hydrocarbons below CZ9 which disappeared during the first few days of adult life. The natural pheromone appears on the pharate adult female about 2 days before emergence from the puparium and is present throughout life. This suggests it is a component of the surface cuticular waxes. Responsiveness of males to pheromone-baited decoys increased to a maximum 3 -4 days after emergence in regularly fed flies and only declined during the 24 h prior to death from starvation.

Adult maleG. pallidipes attempted to copulate with decoys treated with a branched paraffin obtained from laboratory-reared female flies. The compound causing maximal response was isolated and identified as 13,23-dimethylpentatriacontane. The synthesized compound elicited increasing responses with increasing doses. This sex- and species-specific compound was always present in physiological amounts in females, as it increased from 2 μg at emergence to 10 μg per female at 14 days. It was present in wild-caught females from a wide geographical range.