Vitamin D, through food fortification and supplementation, is a promising new health strategy and thus provides opportunities for food industry and nutrition researchers to work together towards determining how to achieve this potential health benefit.

Developmental rate and adult weight were studied at constant temperatures from 9.8 to 27.9°C for 18 clones from each of five populations of the pea aphid, Acyrthosiphon pisum (Harris), from locations between 39 and 53°N latitude in central North America. The response of developmental rate to temperature for each clone was accurately described by a three parameter non-linear equation. Adult weight usually decreased with increasing rearing temperature, but the shape of the response to temperature varied among clones. Variation in the developmental parameters was greater among clones within populations than among populations. No consistent trends were observed in the developmental parameters or adult weights either with latitude or the long term average temperatures at the locations. We conclude that previously reported geographic variation in the developmental threshold of this species, which was attributed to local adaptation, occurred either because the clones tested were not representative of the populations or because rearing methods differed among studies. The results are discussed in relation to the hypothesis that life history traits which are temperature sensitive are adapted to local thermal environments.

Developoment, growth, and survival of larvae and pupae of the red turnip beetle, Entomoscelis americana Brown, were studied in 10 constant and four alternating temperature regimes (10 to 32.5° C), in field-cages, and in natural populations in Manitoba. This beetle has a northtemperate distribution in North America. Larval and pupal development occurs in spring and normally is completed before the end of June. Growth and development occurred at all constant temperatures tested, but survival was low at the extreme temperatures. Therefore, the threshold and upper limit were near 10 and 32.5° C. The developmental times of the sexes did not differ and decreased with temperature, except possibly at 32.5° C. The average weight of adult females increased with temperature up to 32.5° C and those of males up to 25° C. Considering developmental rate, survival, adult weight, and incidence of malformed adults, the optimum temperature was estimated to be near 27.5° C.Development was accelerated significantly (6 to 9%) in alternating regimes with temperatures differing by 10° C, but not in regimes differing by 5 and 15° C. All alternating regimes increased adult weight, 5 to 17% for females and 2 to 10% for males. Field cage studies confirmed the increase in adult weight, but not the acceleration in development.A three-parameter normal function described accurately the relationship between developmental rate and constant temperature. A computer simulation model based on this equation estimated developmental times in field cages to within one to five days. For natural populations the model overestimated the developmental times by five to 16 days. The discrepancies between model estimates and observed developmental times in natural populations apparently were due to the elevation of larval and pupal body temperatures above air temperatures by behavioral thermoregulation. The elevation of body temperature was estimated to be equivalent to the addition of 5 to 6° C to the maximum daily air temperature. The adaptations and responses of this beetle to the cool spring temperatures of the north-temperate region are discussed.

The seasonal occurrence and number of generations of Lygus lineolaris (Palisot de Beauvois) were studied on alfalfa (Medicago sativa L.), everbearing strawberries (Fragaria × ananassa Duchesne), oilseed rape (Brassica napus L.), and stinkweed (Thlaspi arvense L.) in field plots at Winnipeg, Manitoba, and in commercial alfalfa and oilseed rape fields throughout the agricultural areas of Manitoba in 1990–1993. Lygus borealis (Kelton) was studied only during 1993. Lygus lineolaris had two non-overlapping generations in southern Manitoba. Overwintered adults migrated onto host plants during die first 3 weeks of May, and females containing chorionated eggs were found in relatively small numbers for 5–6 weeks until the last 3 weeks of June. First-generation nymphs were present from the last half of May until the last half of July. During the last 2 weeks of June, the overwintered adults disappeared suddenly and were replaced completely by first-generation adults. First-generation adults eclosed during the last 2 weeks of June and in July, and first-generation females containing chorionated eggs were present for about 6–7 weeks until mid-August. Second-generation nymphs first appeared in late July or early August and most completed development by the end of September. Second-generation adults were found from the first half of August until they hibernated in October and November. Most second-generation females contained previtellogenic eggs and. therefore, were in reproductive diapause. In 3 of the 4 years, the overwintered adults appeared to include all second-generation adults plus 0–20% of the first-generation adults. The data from commercial alfalfa and oilseed rape fields indicated that the seasonal occurrence of L. lineolaris was relatively uniform in most or all agricultural areas of Manitoba. Lygus lineolaris has one generation (the second generation) on oilseed rape, and the eclosion and dispersal of reproductively active first-generation adults were well synchronized with the bud and flower stages of this host plant in southern Manitoba. In 1993, L. borealis had two generations and its seasonal occurrence was similar to that of L. lineolaris.

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