We investigated the life history consequences of changes in diet between larval and adult life stages in the polyphagous lady beetle Coleomegilla maculata DeGeer (Coleoptera: Coccinellidae). Beetles were reared on three larval diets: greenbug, Schizaphis graminum Rondani (Homoptera: Aphididae), eggs of the flour moth, Ephestia kuehniella Zeller (Lepidoptera: Pyralidae), and bee pollen. The reproductive performance of females was then evaluated on an adult diet of either greenbug or moth eggs. Moth eggs appeared to be the most suitable diet for larvae, yielding the largest adults, and pollen the least suitable, resulting in the smallest adults and greatly extended developmental time. Pollen‐reared beetles tended to have lower fecundity and fertility than those reared on animal protein, regardless of adult diet. Female fitness was generally increased by a change in diet upon emergence to the alternative source of animal protein, suggesting that dietary complementation occurred across life stages. Among females reared on greenbug, a change of diet to moth eggs reduced the period required for production of 12 clutches and increased egg fertility compared to continued feeding on greenbug. Among females reared on moth eggs, a change of diet to greenbug increased fecundity compared to continued feeding on moth eggs. Among females fed an adult diet of greenbug, those fed moth eggs as larvae had faster production of 12 clutches and higher fecundity. We discuss these novel results in the context of coccinellid life history and ecology and their potential implications for other insects that are predatory as both larvae and adults.

Abstract. We examined oviposition decisions by Hippodamia convergens Guérin in semi-natural arenas in the laboratory. Gravid females were presented individually with an array of four young sorghum plants, Sorghum bicolor, bearing (1) no additional stimulus, (2) an established colony of greenbug, Schizaphis graminum Rondani, (3) residues of conspecific larvae, and (4) greenbugs plus residues of conspecific larvae. Females laid no egg masses on type 3 plants, significantly fewer than expected by chance on type 4 plants, and significantly more on type 1 plants, with type 2 plants receiving expected numbers. Females laid 50% of egg masses on elements of the arena other than the plants, especially the cage screen, suggesting that females sought to distance their eggs farther from larval residues than the spacing of plants in the arena permitted (15 cm). When the experiment was repeated with plants exposed to larvae of Coleomegilla maculata DeGeer, the repellency was weaker. Once again, clean plants were the most preferred and aphids did not increase the acceptability of plants with larval residues. Nevertheless, only 18% of egg masses occurred off the plants and larval residues did not reduce the acceptability of aphid-bearing plants as did conspecific larval residues. Simultaneous choice tests conducted with individual third instars of both species revealed that C. maculata larvae consumed H. convergens eggs as readily as conspecific eggs, but H. convergens larvae preferred conspecific eggs to those of C. maculata. We conclude that H. convergens oviposition decisions are shaped by the risks of both egg cannibalism and predation.

In spring 2003, several outbreaks of the Russian wheat aphid, Diuraphis noxia (Mordvilko), were reported in fields of supposedly resistant wheat cultivars ('Stanton', 'Halt', and 'Prairie Red') in eastern Colorado. We conducted two laboratory experiments to compare the biological performance of this new biotype 2 (B2) to that of two D. noxia collections of biotype 1 (B1) from western Kansas by using three wheat cultivars as host plants: 'Trego', a susceptible cultivar, and Stanton and Halt, two cultivars with different genetic sources of resistance. Survival of solitary nymphs from first instar to adult for the two clones of B1 on Trego was 96 and 90%, respectively, compared with 67 and 43% on Stanton, and 65 and 57% on Halt. In contrast, B2 had 60% survival on Trego, 43% survival on Halt, and 85% survival on Stanton. One clone of B1 required longer to mature on Halt compared with Trego or Stanton, but no other differences in developmental time among cultivars were significant. The standardized fecundity of solitary foundresses of the B1 clones was 19.6 and 20.1 nymphs on Trego, compared with 4.6 and 0.9 on Stanton, and 2.8 and 1.1 on Halt, respectively, over the same period. In contrast, fecundity of B2 was 21.1, 20.8, and 19.7 on Trego, Stanton, and Halt, respectively. When larger colonies developed on individual plants over longer periods, Trego supported the largest number of B1 aphids by experiment's end, whereas Stanton and Halt yielded the largest numbers of B2. The order of overall plant damage was Trego > Stanton > Halt when infested with B1, with no significant differences for B2. Trego had more pronounced leaf rolling than other cultivars, independent of biotype. Collectively, the results suggest that D. noxia B2 from Colorado has evolved cross-virulence to both Dn4- and Dny-based resistance sources.

Foliar and soil-drench insecticide treatments were used in attempts to manipulate infestation of cultivated sunflower plants, Helianthus annuus LeConte (Asterales: Asteraceae) by Dectes texanus LeConte, (Coleoptera: Cerambycidae) a serious pest of sunflowers in the High Plains of the USA. Seed yields were assessed on a per-plant basis for both oilseed and confection type sunflower hybrids in two years. Both insecticide treatments (foliar ë-cyhalothrin and soil-drench carbofuran) improved yield of oilseed sunflowers in 2004, but not in 2005. Yield of confection hybrids was improved by a systemic fungicide (thiophanate methyl) in 2005, but insecticides did not improve yield in either year. Both insecticide treatments gave good control of various stalk-boring insects such as Cylindrocopturus adspersus (Coleoptera: Curculionidae), Mordellistena sp. (Coleoptera: Mordellidae), and Pelochrista womanana (Lepidoptera: Tortricidae), but neither gave better than 50% control of D. texanus. Plants were sorted according to the presence or absence of D. texanus larvae and no reduction was found in total seed weight, seed size, or oil content as a result of infestation. However, mature larvae of D. texanus girdle stalks at the base in preparation for overwintering, a behavior that reduced stalk breakage force by 34–40%, leading to yield losses through lodging. At harvest in 2005, there were differences between cultivars and among treatments in the proportions of D. texanus larvae that had girdled their plants at harvest. It was concluded that further research aimed at reducing crop losses to D. texanus should focus on means of delaying stalk desiccation and/or deterioration, factors that appear to trigger girdling behavior.

Biotype 2 of the Russian wheat aphid, Diuraphis noxia (Mordvilko), is virulent to both sources of resistance presently available in commercial wheat, Triticum aestivum L. The performance of biotype 2 was compared with that of biotype 1 on eight wheat cultivars at two constant temperatures, and the plants were evaluated for overall damage and leaf rolling. Colonies of biotype 2 grew an average of 2.3 and 24.9 times faster in the first and second generation, respectively, than did their biotype 1 counterparts at 20°C, reaching 80 to 125 aphids per plant after 20 d, compared with 10 to 31. The no. of aphids per plant at 10 and 20 d after infestation displayed a significant biotype–temperature interaction. There was also a biotype–temperature interaction for plant damage at 10 d, and for damage and leaf rolling at 30 d. After 20 d at 24°C, damage ratings ranged from 7.3 to 8.6 on a scale of 1.0 to 9.0, and leaf rolling ranged from 2.4 to 2.9 on a scale of 1.0 to 3.0 for biotype 2, whereas values for biotype 1 ranged from 2.8 to 5.1 and 1.4 to 2.2, respectively. There were no differences among cultivars in plant damage or leaf rolling induced by biotype 2, and ratings of both were higher than for biotype 1 in all cultivar–temperature combinations. Biotype 2 D. noxia has overcome both Dn4‐ and Dny‐based sources of resistance, was more virulent than biotype 1 to all the cultivars tested, and induced plant injury more rapidly than biotype 1, especially at higher temperatures.

The cabbage maggot, Delia radicum (L.) is an important insect pest of eruciferous crops in upstate New York. This species causes considerable damage to seedlings and young plants by feeding on roots and stems, resulting in plant stand loss and yield loss. Five crucifer accessions (Brassica oleracea variety italica L.,'Green Comet'; B. oleracea L.,'Rapid Cycling' [Crucifer Genetics Cooperative 3-1 ]; B. oleracea variety botrytis L., a standard cauliflower cultivar'Amazing'; B. carinata L.; and Sinapis alba L., 'Cornell Alt 543') were evaluated to identify sources and mechanisms of resistance for D. radicum. Of the accessions tested, S. alba Cornell Alt 543 demonstrated reduced oviposition by D. radicum, reduced weights and survivorship of larvae, pupae or adults, and reduced damage to plants. Thus, S. alba Cornell Alt 543 could be a potential source for resistance to be bred into cruciferous crops for control of D. radicum.

A 2 yr (1999–2000) study using water-pan traps in the field indicated four generations, including the spring generation, of cabbage maggot adults, Delia radicum (L.), in upstate New York. On average over the 2 yrs, an accumulation of 160.7 ± 8.1 degree-days and 120 ± 3 Julian-days was required for the first adult emergence of flies from overwintered puparia (spring generation). The emergence of 10% of the population required a mean accumulation of 176.6 ± 3.8 degree days and 122.0 + 1.0 Julian days, 25% emergence required 204.2 ± 2.3 degree days and 125.0 ± 1.0 Julian days, 50% emergence required 251.3 ± 3.5 degree-days and 129.3 ± 1.5 Julian days, 75% emergence required 297.6 ± 30.4 degree-days and 132.0 ± 0.0 Julian days, and 95% emergence required 390.9 ± 10.1 degree days and 141.0 ± 3.0 Julian days. From the emergence of the first adult flies, the population required a mean accumulation of 449.2 ± 1.4 degree days to complete the spring emergence. For complete emergence of flies, the F1 generation required a mean accumulation of 508.4 ± 32.9 degree days, the F2 generation required 465.3 ± 21.5 degree days and the F3 generation required 399.1 ± 3.1 degree days. With the help of a degree-days model, it is possible to predict fly emergence in the spring and succeeding generations. This model can help growers minimize insecticide use through better timing of treatments or adjustment of planting dates. In addition, this model will be useful in developing sampling plans and control strategies for immature stages of cabbage maggot.

Changes in Þtness parameters as a function of colony size (one versus 10 aphids) were measured in two biotypes (RWA1 and RWA2) of the Russian wheat aphid, Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), feeding on three cultivars of wheat, Triticum aestivum L., at two temperatures. ÔTregoÕ is a cultivar with no speciÞc resistance to D. noxia, whereas, ÔStantonÕ and ÔHaltÕ express Dny and Dn4 resistance sources, respectively. Feeding in a group accelerated the development of RWA1 on Trego and Stanton at 20ЊC, but not at 24ЊC, whereas grouped RWA2 developed faster than solitary RWA2 on all three cultivars at 24ЊC, but not at 20ЊC. Survival (Þrst instarÐadult) of RWA2 also was improved by grouping on Stanton and Halt at 24ЊC, but solitary RWA2 survived better at 20ЊC on all three cultivars. The reproductive rate of RWA1 was improved by grouping on Trego and Stanton at both temperatures, but only on Halt at 24ЊC. Lifetime fecundity of RWA1 also was increased by grouping in all cases except for Trego at 20ЊC. Grouped development increased the reproductive rate of RWA2 on all three cultivars at 24ЊC, but had no effect at 20ЊC. Grouped RWA2 developed and reproduced faster than grouped RWA1 on all three cultivars at 24ЊC. Thus, the Þtness of D. noxia was positively correlated with group size during colony establishment, but the effects were sensitive to temperature, being more pronounced at 20ЊC for RWA1 and at 24ЊC for RWA2.