Optimum size of a sample unit and within-branch distribution of overwintering spruce budworm were determined for black spruce in northern Maine. No significant differences in sample reliability were found between whole-branch and 45-cm branch-tip samples. Larval distribution on branches varied with total branch length and a model was developed to estimate the whole-branch population from a 45-cm branch tip. Use of a 45-cm branch-tip sample unit is recommended because it is biologically and statistically valid and reduces sampling costs.

The susceptibility of 31 species of agricultural insect pests representing 7 families of Lepidoptera, 3 of Diptera, and 3 of Coleoptera to the entomogenous nematodes Steinernema feltiae Filipjev and Heterorhabditis bacteriophora Poinar, were investigated in the laboratory. Of the 27 species found susceptible to S. feltiae, 19 are reported for the first time. Of the 21 species killed by H. bacteriophora, 15 are reported for the first time. The Lepidoptera as a group were highly susceptible to the nematodes. On the basis of larval mortality caused by the nematodes, of nematode reproduction in insect cadavers, and of the known economic importance and life histories of the test insects, S. feltiae was judged to warrant further research as a possible biological-control agent against Euxoa ochrogaster (Guenée), E. auxiliaris (Grote), Agrotis orthogonia (Morr.), Actebia fennica (Tauscher), Mamestra configurata Walker, Delia radicum (L.), D. antiqua (Meig.), and Zygogramma exclamationis (F.).

Thirty-four species of insects associated with Scolytus multistriatus (Marsham) were reared or collected from several species of elm collected throughout California. Few of these species occurred in large numbers and many of their ecological roles in this subcortical habitat are unknown. Predators were uncommon; only 6 species of parasitic Hymenoptera were reared, 3 of which were not previously known from California. One, Dendrosoter protuberans (Nees), had previously been released for biological control of S. multistriatus only as far west as Colorado. The most abundant insect associate reared from northern California, Cheiropachus quadrum (F.), exhibited a maximum percentage parasitism of 2%. Seven species of mites, including 2 new species, were also collected in association with S. multistriatus.

Predatory arthropods were sampled in high-maintenance Kentucky bluegrass lawns (lawns under commercial lawn care), low-maintenance Kentucky bluegrass lawns (under minimal care), and low-maintenance tall-fescue lawns. In general, tall fescue supported fewer predators than Kentucky bluegrass, specifically the families Erigon-idae, Linyphiidae, and Carabidae. Populations of Erigonidae, Linyphiidae, and Carabidae were lower in high-maintenance bluegrass than in low-maintenance bluegrass. The carabids Amara cupreolata Putzeys, Agonum punctiformum (Say), and Harpalus (Pseudopkonus) spp., and a staphylinid, Philonthus sp., were particularly uncommon in high-maintenance sites. Hierarchical classification of sites suggested that the structure of the staphylinid and carabid communities differs in tall fescue and Kentucky bluegrass turf, and differs in high- and low-maintenance bluegrass.

The New World species of Trissolcus, exclusive of the flavipes and thyantae species groups, are revised. This encompasses seven species: T. basalis (Wollaston) recorded in the southeastern USA, West Indies, Venezuela, and southeastern Brazil; T. cosmopeplae (Gahan) from the USA and Canada; T. erugatus n. sp. from the western USA and Canada; T. hullensis (Harrington) widely distributed throughout Canada, USA, Mexico, Dominica, and Venezuela; T. radix n. sp. from Guatemala, Costa Rica, Colombia, Venezuela, and the southeastern USA; T. solocis n. sp. from Mexico and the southeastern USA; and T. utahensis (Ashmead) from the western USA and Canada. Available host information for each species is summarized. These species are described and an identification key is provided.

Attraction of male Choristoneura spp. to various mixtures of the pheromone components of C. occidentalis Freeman and C. retiniana (Walsingham) released at various rates was evaluated at several sites in western North America. At all but 1 location, male trap capture increased with progressively greater release rates of a 92:8 mixture of (E)- and (Z)-11-tetradecenals (TDALs), previously identified as active components of the attractant pheromone of C. occidentalis. Similarly, trap catch was positively correlated with release rate of an 84:7:8:1 mixture of (E)- and (Z)-11-tetradecenyl acetates and (E)- and (Z)-11-tetradecenols (1:0.1 TDACs:TDOLs), previously identified as active components of the attractant pheromone of C. retiniana. All release rates of TDALs attracted only C. carnana (C. occidentalis and C. carnana probably are subspecies of the same species) in the central Sierra Nevada, but in the southern Cascades all but the lowest release rate of TDALs attracted significant numbers of males classified as C. retiniana in addition to those classified as C. occidentalis. At all locations, 1:0.1 TDACs: TDOLs exhibited complete species specificity, attracting only C. retiniana at all release rates tested. The 1:0.1 ratio of TDACs: TDOLs was the most attractive mixture of these components to C. retiniana. Addition of 1:0.1 TDACs: TDOLs did not significantly affect attraction of C. carnana to TDALs. However addition of TDALs significantly decreased attraction of C. retiniana to 1:0.1 TDACs:TDOLs.

Embryogenesis, embryo survival, and hatching were studied in eggs of the red turnip beetle, Entomoscelis americana Brown, incubated at 9 constant temperatures (5–35 °C) for 5–50 days before cold storage at −5 °C for 200 days during winter. Embryogenesis occurred at all temperatures tested, but the threshold and upper limit for embryogenesis were near 5 and 35 °C, respectively, and the optimum-temperature range was about 12.5–20 °C. Embryo survival was about 12–65% lower in eggs incubated at 5 °C for 50 days and at 7.5 and 10 °C for 30–50 days than in those incubated at these temperatures for shorter times, indicating that prolonged exposure to temperatures near the threshold during embryogenesis adversely affects the embryos. Embryo survival declined to low levels in eggs incubated at 25 and 30 °C for more than 30 and 5 days, respectively, and only a small number of embryos survived in those incubated at 35 °C for 5 days. The times to 50% hatch in eggs that contained late-stage embryos before cold storage and had been incubated at 25, 30, and 35 °C were 1.6, 2.6, and 6.5 times longer, respectively, than in those at 12.5–20 °C. These results indicate that embryos incubated at 25–35 °C during embryogenesis before diapause require a recovery period before initiating the normal postdiapause events, and that these events can be adversely affected by unfavorably high temperatures before diapause. The physiological and ecological significance of the data is discussed.

In laboratory colonies, 8 temperate Bombus Latreille species and the tropical montane species, B. ephippiatus Say, had significantly more first-brood workers, more rapid worker development time, and faster rates of worker production than the tropical lowland species, B. atratus Franklin. Bombus ephippiatus did not differ from most temperate species in any of the 3 characters. Differences in these bionomic characters among arctic, temperate, and tropical Bombus are assessed in terms of latitudinal trends.

Under axenic conditions, larvae of Delia antiqua develop to the adult stage on onion agar only if the agar is supplemented with mixtures of 10 essential amino acids and 8 water-soluble vitamins. The omission of the amino-acid mixture allowed no development past the first instar. When the vitamin mixture was omitted, 1 of 25 larvae developed to the pupal stage. Omission of individual vitamin supplements caused less marked effects. Omitting supplemental choline, thiamine, pyridoxine, or pantothenic acid had no significant effect on development. Omitting supplemental biotin or nicotinic acid resulted in suboptimal development to the adult stage. Omitting riboflavin or folic acid resulted in development to the adult stage, but the adults did not lay viable eggs. Presumably nutrients that are in insufficient supply in onion tissue are supplied by bacteria in nature.

The species previously recognized as Euxoa ridingsiana (Grt.) is shown to be composed of a sympatric pair of sibling species, Euxoa ridingsiana (Grt.) and Euxoa maimes (Sm.), which in the laboratory will produce viable F1 hybrids but no F2. Results of F1 sib and backcrosses show that the F1 males are fertile and the F1 females are infertile. In mating-bias tests conducted in laboratory cages, 74% of matings were conspecific and 26% interspecific. Differences in the diel periodicities of mating, which are about 2 h out of phase, may account for the mating bias. The duration of development of E. ridingsiana in the laboratory and its seasonal flight period in the field are about 2 weeks in advance of that of E. maimes. However, there is considerable overlap of the flight periods and, with the tendency of females of both species to mate several times, it is unlikely that the difference in seasonal emergence is enough to effect reproductive isolation. It is evident that, under natural conditions, reproductive isolation can be maintained entirely by species-specific sex pheromones. This mechanism of reproductive isolation is, however, apparently ineffective when moths are confined in cages in the laboratory.

Biogeographic considerations suggest that the differences in life-cycle timing and mating periodicities might have been adaptations to adjust development and reproduction to prevailing ancestral environments. If the initial differentiation of the 2 species occurred in isolation and included at least an incipient shift in the pheromonal mate-recognition system, it is possible that upon reestablishment of contact between ancestral populations the differences in life-cycle timing and mating periodicities acting in concert could have effected substantial, albeit incomplete, reproductive isolation. Subsequent selection to reinforce assortative mating to preserve coadapted gene complexes could then have resulted in differentiation of discrete pheromonal systems and attainment of species status.

The sex-pheromone components of the sibling species Euxoa ridingsiana and Euxoa maimes were identified in abdomen-tip washes and extracts of calling female moths. Both species produced the same primary pheromone component, (Z)-9-tetradecenyl acetate (i.e. Z9-14:Ac), but they produced different amounts of secondary pheromone components. In the field, male moths of E. ridingsiana were specifically attracted to a 3-component blend of Z7-12:Ac, and Z7-14:Ac, and Z9-14:Ac in a ratio of 1:2:40 at 500 μg per dispenser, and males of E. maimes were specifically attracted to a 5-component blend of Z7-14:Ac, Z9-14:Ac, Zl 1-14:Ac, Zll-16:Ac, andZll-16:OH in a ratio of 1.5:500:5:50:2.5 at 500 μg per dispenser. Both synthetic pheromone blends were competitive with conspecific females. These pheromone analyses confirm that E. ridingsiana and E. maimes are valid biological species that can maintain their reproductive isolation solely by specific sex pheromones.

The beet leafhopper, Circulifer tenellus (Baker), was found to be significantly attracted to the color yellow. Yellow, opaque plastic cards coated with a sticky substance were shown to be an effective survey tool for monitoring adult beet leafhopper. Traps with different hues of yellow (wavelengths of 510 and 588 nm) showed no significant differences between trap catches. The commonest flight strata at a host site was at ground level, where significantly higher numbers of adults were trapped than at heights of 0.3, 0.6, 0.9, 1.5, 2.1, and 2.7 m above the ground. The ground level is the optimum location for a yellow sticky trap when monitoring C. tenellus.

Vol. 116, 1984. pp. 1591-1603.

A biosystematic revision of the genus Stenonema (Bedmarik, A.F., and W.P. McCafferty.