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Can. Ent. 113: 127-131 (1981) The life history of Plutella xylostella (L.) was studied in plantings of Brussels sprouts at Cambridge, Ontario in 1977 and 1978. Adults were monitored by using sticky traps constructed of bristol board; eggs, larvae, and pupae were monitored by sampling plants.In both years in the spring, some of the first eggs were found before adults were caught in the traps. The trap collections indicated four periods of adult flight each year. During the last period of flight in 1977 eggs were laid; however, the fifth generation was not completed. Day-degree analyses of the populations indicated that 293 day-degrees (C) above a threshold temperature (7.3"C) were required to complete one generation. Using day-degree accumulations it was possible to predict accurately the periods when various stages of the pest were dominant even though there was considerable overlap of various stages in the field. I977*Following a decrease in the number of pupae per plant. tPeak numbers of moths trapped on sticky boards. $Based on 283 day-degrees above a threshold of 7.3"C (Harcourt 1954). §Estimated on the basis of eggs found.

Can. Enr. 111: 1389-1393 (1979) A modified Ladell apparatus is described which offers a low cost and efficient method of wetland macroinvertebrate extraction. Soil and leaf litter samples, immersed in Mg,SO, solution, are subjected to agitation and bubbling to promote the extraction of macroinvertebrates. A further modification provides salt solution recycling. Fourteen floodplain taxa were recovered with extraction efficiencies ranging from 80 to 100% at a cost of 15-20 cents (U.S.) per sample.

The cabbage maggot, Hylemya brassicae (Bouché), had three generations per year from 1970 to 1973 inclusive, a partial fourth was noted in most years. A small proportion of first generation pupae entered aestivation in 1971.Thermal units required for fly emergence from overwintered pupae fell within a narrow range (174 to 199), but there was little correlation between thermal units and fly emergence in subsequent generations. Lack of adequate moisture delayed establishment of larvae in roots in some generations. Lack of adequate soil moisture delayed establishment of larvae in roots in some generations, and this appeared to be the chief reason for the lack of correlation between thermal units and fly peaks.Throughout this investigation the over-all population remained remarkably constant. Parasitism by a staphylinid, Aleochara bilineata Gyll., and a fungus, Strongwellsea castrans Batko and Weiser, and soil moisture were the most important biological and climatic factors affecting survival. Parasitism of the adult by a nematode, Heterotylenchus sp., was recorded for the first time.Although large numbers of seed maggot adults, Hylemya florilega (Zett.) and H. platura (Meig.), were recorded, few infested rutabaga. Other species trapped included Euxesta notata (Weid.) and Muscina spp.