The solitary, pupal parasitoids Spalangia spp. Muscidifurax raptor oviposited supernumerary eggs on house-fly pupae exposed at 3 poultry farms in north central Florida. The percentage total parasitoidism at the 3 sites was 23.7%, 33.6%, and 77.5%, while the percentage of the hosts containing supernumerary parasitoids was 6.2%, 10.7%, and 55.8%, respectively. The average number of parasitoids found per parasitoidized pupa ranged from 1.45 to 2.96. The parasitoids did not show a density-dependent response to spatial variation in host density. Among aggregates of hosts that contained at least 1 parasitoid, percentage total parasitoidism either decreased as host density increased or was unrelated to host density. When total parasitoidism was low, females tended to avoid already parasitoidized hosts. When total parasitoidism was high, more of the hosts contained multiple parasitoids than a single parasitoid.

Three native species of parasites and 3 hyperparasites were reared from pupae of the European winter moth, Operophtera brumata (L.), and the Bruce spanworm, O. bruceata (Hulst), collected in the Victoria area of Vancouver Island, British Columbia, in 1981. Two of the pupal parasites also attacked other species of Geometridae. Two species of hyperparasites attacked Cyzenis sp., and the third parasitized ichneumonid primary parasites of Operophtera spp. The hyperparasites may have a negative impact on the biological-control agents, Cyzenis albicans (Fall.) and Agrypon flaveolatum (Grav.). Total parasitism by pupal parasites of the Operophtera host complex was about 4%. Descriptions and illustrations of cephalic structures of final-instar larvae of the parasites and a key for their separation are given.

The numbers of larvae and pupae of the gypsy moth, Lymantria dispar L., were monitored in southwestern Quebec from June through August 1980 at 13 sites. In 10 sites, the proportion of male pupae was significantly different from an expected proportion of 0.5. Linear-regression analyses of the proportion of male pupae on larval density showed a significant increase in the number of male pupae with increasing larval density. Changes in the sex ratio could be an important indicator of the dynamic state of a population, and should be considered in modeling the population dynamics of gypsy moth.

Microctonus vittatae Mues. oviposit in the hemolymph of flea beetles, Phyllotreta striolata (F.) and Phyllotreta cruciferae (Goeze), by inserting the ovipositor into the host's mouth and occasionally, membranous areas between body segments. Some of the eggs are transported in the hemolymph posteriorly from the head to the thorax or abdomen, and some laid in the thorax are carried into the abdomen, but eggs hatch in all 3 body regions of the hosts. First-instar larvae that eclose in the head and thorax disperse into the abdomen where they develop. Egg and larval dispersal into the abdomen increase the probability that the parasite has adequate space for development.

During 1983, collections and observations of the half-wing geometer, Phigalia titea (Cramer), were made in 2 counties of eastern West Virginia where the species had caused heavy defoliation of hardwoods in the previous 2 years. Larvae were observed on 41 species of host plants in the field. Host–plant evaluations for 69 species were made in the laboratory with 1st-instar larvae. According to criteria of response/developmental time of larvae, 33 plants were categorized as highly acceptable, 12 as acceptable, 20 as unacceptable, and 4 as toxic.

The calling of female blueberry spanworms occurs primarily during the first few hours of the photophase under controlled laboratory and field conditions. Peak calling occurred 2 h after lights-on at laboratory test temperatures of 20,15, and 10 °C under a light:dark regime of 16:8; duration of calling was prolonged at 10 °C. Under continuous scotophase, female calling activity free-runs at a natural periodicity of ca. 27 h. However, under continuous photophase the circadian rhythm is damped to a low level of activity but maintains a ca.24-h periodicity.

Development rates of the parasitoid, Trichogramma minutum Riley, were studied to provide information required in timing field releases of T. minutum for suppression of egg populations of the spruce budworm, Choristoneura fumiferana (Clemens). Development was observed in eggs of 2 host species, C. fumiferana and Sitotroga cerealella (Olivier), at constant temperatures of 14, 21, and 27 °C. Parasitoid development varied directly with temperature. Parasitoids developed more rapidly in eggs of S. cerealella than in those of C. fumiferana. Parasitoid males developed faster than females in some host-temperature treatments. Development of T. minutum is apparently rapid enough to allow progeny of parasitoids released early in the spruce budworm's oviposition period to mature and be available to oviposit in budworm eggs deposited later in the budworm oviposition period. Potential release strategies are discussed.

Using a slide-dip bioassay, Psylla pyricola Forester from intensively sprayed, minimally sprayed (IPM), recently abandoned, and long-abandoned pear orchards in the Hood River, Rogue River, and Willamette valleys of Oregon were surveyed for resistances to azinphosmethyl, endosulfan, Perthane®, and fenvalerate. Lethal-concentration (LC50) values showed resistance levels from 12- to 41-fold to azinphosmethyl and 5- to 12-fold for endosulfan in selected populations. Resistance patterns did not correlate with orchard-treatment histories in the Hood River and Rogue River valleys, where even long-abandoned orchards harbored resistance psylla. There was better association between treatment histories and resistance levels in populations from the more widely scattered orchards in the Willamette Valley. A regional analysis of mean LC50 values indicated that psylla resistance was significantly higher to azinphosmethyl in the Rogue River Valley and to endosulfan in the Hood River Valley. Regional resistance levels for these compounds reflect differences in intensity of past use. A regional hypothesis is proposed to explain the patterns of resistance developed in the Hood River and Rogue River Valleys, where pear production is intensive as opposed to the more localized patterns of resistance in the Willamette Valley. Applications of results to the management of resistance are discussed.

To assess whether canola seed is more susceptible to infestation than rapeseed, the food preferences, survival, and development of 4 major insect pests of stored products were tested in the laboratory on seeds of 10 cultivars of rapeseed and canola. Adults of the merchant grain beetle, Oryzaephilus mercator (Fauvel), the sawtoothed grain beetle, O. surinamensis (L.), and the red flour beetle, Tribolium castaneum (Herbst) preferred cereal diets on which they are normally reared to any of the rape or canola cultivars. The rusty grain beetle, Cryptolestes ferrugineus (Stephens), preferred wheat kernels of 15% moisture content to these cultivars. Insects did not prefer any one of the rape and canola cultivars, and attempted to avoid them. Survival of the 4 species was higher and developmental time shorter on control diets than on the rape and canola cultivars. Oryzaephilus mercator produced only a few progeny on cv. Zephyr, and T. castaneum on cvs. Midas and Tower. No correlations were found between survival or development time and glucosinolate or erucic-acid content. Much higher survival of O. mercator occurred when tests were started with newly emerged larvae than with eggs. Survival was substantially lower on ground than on whole seeds. No evidence was found to indicate that canola seed is more susceptible to infestation than rapeseed.

From 1981 to 1984, a low-spray management program was employed against injurious arthropods on the 40 disease-resistant apple trees in my experimental orchard in Massachusetts. The program consisted of an annual early-season application of petroleum oil followed by 2 applications of phosmet (1 at petal fall and another 10–14 days later). Visual traps were used to suppress Rhagoletis pomonella flies. For all years combined, a mean of 89.7% of fruit sampled at harvest in this orchard was free of insect injury compared with 0% uninjured fruit on neighboring unsprayed trees. Populations of foliar-feeding pests never reached injurious levels.

The efficacy of Bacillus thuringiensis was evaluated against the large aspen tortrix on trembling aspen in Alaska. A concentration of 4 × 109 IU per 378.5 L of water was applied to infested trees using a hydraulic sprayer. Treatments with Dipel 4L and Thuricide 32LV resulted in population reductions of 69 and 76% respectively. Both products provided significant foliage protection. Timing of treatment is critical to successful population suppression and foliage protection.

Losses in yield of spring wheat due to infestations of Sitodiplosis mosellana (Géhin) were determined for 700 000 ha of arable land in northeast Saskatchewan, Canada in 1983. The proportion of kernels infested (y) was a power function of the number of wheat-midge larvae (x) (y = 35.3x0.725). One, 2, 3, and 4 larvae per kernel resulted in a level of infestation of 38, 58, 78, and 96%, respectively. There was no significant difference between infestation levels from fields sampled at the heading stage of crop growth and the estimates of infestation levels for these fields at harvest time. Yield of grain (y) was negatively exponential to an increase in level of infestation (x) (ln y = 5.7−0.017x). Infestations of 30, 60, and 90% reduced yields of spring wheat by 40, 65, and 79%, respectively. The average decrease in crop yield in the study area was about 30%, which resulted in estimated losses in total gross revenue of about $30 million.

The genus Zacremnops Sharkey & Wharton is erected to include 2 New World species formerly placed in Megagathis Kriechbaumer. Phylogenetic relationships between Zacremnops and selected genera of Agathidinae are briefly discussed.

Females of the polyphagous ichneumonid parasitoid, Exeristes roborator (F.), that were conditioned for 10 days to hosts in a specific habitat demonstrated associative learning by responding with ovipositor probes into the habitat alone. Females conditioned immediately after eclosion showed a higher participation rate, intensity, and duration (approximately 7 days) of learned behavior than those conditioned 5 or 10 days after eclosion, despite the fact that newly eclosed females did not probe for hosts with their ovipositors until 4 or 5 days after eclosion. The reduction in the learning ability of females within a short time after eclosion may impart a selective advantage to E. roborator by reducing the costs of learning. It could also reflect developmental constraints on the process of learning. The results suggest that carefully controlled associative learning could be exploited to improve the efficiency of host location by parasitoids released in biological-control programs.

Mathematical discussions of models of functional response (predation rate as a function of prey density) have usually emphasized description of the shape of the functional-response curve. However, lack of congruence between experimental design and data analysis and under-utilization of appropriate statistical methods of analysis have hindered an empirical synthetic treatment of such feeding behavior. Here we review existing experimental and statistical procedures with reference to Holling's generalized model of functional response, and describe: (1) an experimental design compatible with the assumptions of the model; (2) a maximum-likelihood method for fitting the model; (3) several methods for statistical comparison of sets of functional-response curves; and (4) an exploratory graphical method for examining patterns of variation among larger numbers of samples.

The Holling disc equation (Type-II functional response) for predation, which is mathematically equivalent to the Michaelis–Menten enzyme-kinetics and to the Monod microbial-growth equations, has been used in several linear transformations for parameter estimation. The most commonly used is the Lineweaver–Burk double reciprocal. We compare 4 linearizations of the disc equation and a direct nonlinear fit to stimulated predation data. We conclude that (1) the best parameter estimates are obtained by the direct nonlinear method and (2) the Lineweaver–Burk is the worst of the (all unsatisfactory) linearizations. We propose a new nonparametric technique to use when nonlinear methods cannot be used.

On 2 occasions in August 1983, during the course of a study of the arthropod community associated with collards (Brassica oleracea L. [Cruciferae]) in central New York State, the pentatomid bug Euschistus servus euschistoides (Vollenhoven) was observed feeding on larvae of the imported cabbage butterfly, Pieris rapae (L.). The individuals making the attacks, both adults, were discovered on the upper surface of a collard leaf with 4th-stage caterpillars firmly impaled on their rostra. Both caterpillars appeared lifeless. In 1 case, the P. rapae larva appeared somewhat shrunken, indicating that the bug had probably removed some body fluids from it. Voucher specimens of the bug have been deposited in the Cornell University Insect Collection (lot #1137). This note constitutes another record of predatory behavior exhibited by this nominal phytophage (Esselbaugh 1948; McPherson 1982).

The peach-twig borer, Anarsia lineatella (Zeller), is one of the most important pests of peaches, almonds, and other stone fruits in the western United States (Bailey 1948), with larvae infesting both twigs and fruit. Infested fruit cannot be marketed and twig injury is damaging to young trees because the young worms burrow into the tender terminal growth of the twigs and cause the rapidly growing twigs to wilt. In this way, infestations by the peach-twig borer interfere with development in young orchards (Newcomer 1966).