Ixodes cookei Packard required ca. 14 weeks to complete development under laboratory conditions, using groundhogs [Marmota monax (L.)] as the blood meal source and off-host conditions of 25–29°C and 93–100% relative humidity. All three post-embryonic instars engorged in ca. 6–8 days. Larvae and nymphs maintained at 25°C moulted to the next instar ca. 18–20 days after detachment. Moult occurred under conditions of either a 0L:24D or a 16L:8D photoperiod. Adult females increased in weight ca. 49-fold from the unfed to the engorged state, attaining a weight of 194.1 ± 15.0 (mean ± SE) mg and producing 1281.5 ± 139.1 (mean ± SE) eggs at 29°C. The pre-ovipositional and ovipositional periods were 4.7 ± 0.3 and 20.2 ± 1.7(mean ± SE) days, respectively, at 29°C. Fifty percent of eggs were deposited within the 1st week of the ovipositional period at 29°C. First egg hatch at 29°C occurred ca. 31 days after oviposition was started. Eggs maintained at 10°C did not hatch, and the thermal threshold for egg development was calculated to be 11.2°C.

Removal sampling, sweepnet sampling, and visual count sampling conducted while walking at constant velocity through a field were used to sample populations of adults of five coccinellid species in plots established in spring wheat fields, Triticum aestivum L. Estimates of absolute population density obtained from two 20-min removal samples taken from each of six 5- by 5-m sub-plots per plot proved reliable and were used to convert estimates obtained from sweepnet sampling (180 sweeps per plot) and visual counts (36 min per plot walking at 10 m/min) into absolute estimates of population density. Population density estimates obtained by removal sampling were quite precise except for species with low capture efficiencies and low population densities.

Crop plant growth stage influenced the numbers of beetles caught in sweepnet samples and was incorporated in regression models for converting sweepnet catch to absolute density. Values of R2 of regressions ranged from 0.51 to 0.90, depending on species. Visual counts were influenced by temperature and aphid density, and these variables were incorporated in regression models. Values of R2 for regressions relating visual counts to population densities ranged from 0.63 to 0.94, depending on species.

The structure and temporal control of insect life cycles can best be understood by viewing them as pathways along which various options (e.g. develop or enter diapause; grow rapidly or grow slowly) are chosen in response to environmental controls such as photoperiod and temperature. Simple life cycles include small numbers of such options. The combination of several successive simple elements, however, can produce remarkably complex life cycle patterns, which are more prevalent than most entomologists have recognized. The ways in which these simple elements contribute to life cycle pathways are outlined and illustrated schematically. Flow charts showing the successive decision points in the life cycle then are constructed for selected species. This approach confirms the different simple elements, and shows how they are used in combination to control seasonal life cycles in nature.

When carrot rust fly, Psila rosae (Fab.), collected as mature third-instar larvae on three dates in each fall of 3 years from carrots from the Holland Marsh, Ont., pupated in the laboratory at 10°C, the intensity of the diapause induced was lower in the samples collected latest in the season. Similarly, the latest pupating cohorts of pupae formed in the field exhibited less intense diapause and developed more rapidly at 20°C in the fall or the following spring. When larvae were kept at 1 or −2°C for varying periods before pupation at 10°C, the incidence and intensity of the pupal diapause decreased with increasing duration of exposure to the low temperatures. Larvae held at 5°C pupated in less than 60 days and entered diapause. Transfer of puparia from 20 to 10°C at various stages of pupation showed that diapause was induced if pupae were transferred less than 48 h after formation of the pupa was first evident.

Larvae of one pyralid, five noctuid, and one geometrid species were exposed to six species/strains of steinernematid and two species of heterorhabditid nematodes applied to soil surface in the laboratory. The most parasitic nematodes were Steinernema bibionis Bovien for the wax moth (Galleria mellonella L.) and the bertha armyworm (Mamestra configurata Wlk.), Heterorhabditis heliothidis (Khan, Brooks, and Hirschmann) for the cereal armyworm [Pseudaletia unipuncta (Haw)], S. feltiae Filipjev Mexican for the variegated cutworm [Peridroma saucia (Hbn.)], and S. feltiae All for the red-backed cutworm [Euxoa ochrogaster (Gwen)] and the spring cankerworm [Paleacrita vernata (Peck.)]. When both LD50 values and rates of parasitism of the hosts were considered together, the most promising nematode for soil applications was S. feltiae against the bertha armyworm.

A simulation model was developed for the population dynamics of a carrot weevil, Listronotus oregonensis (LeConte), population on muck-grown carrots. The model includes mortality rates of eggs, larvae, and pupae for different sowing dates of carrots. It also incorporates the overwintered adult density, the temperature-dependent growth rates of the above-mentioned life stages, the age-, temperature-, and phenology-dependent oviposition rates, and the impact of an egg parasitoid, Anaphes sordidatus (Girault), on egg mortality rates. Model output was evaluated by comparing simulated results with observed results on the seasonal totals and time of population peaks of the egg and larval populations. The mean percentage differences between the simulated and observed seasonal egg totals were 3.1 ± 0.66 (SE) in 1987 and 1988, and 4.2 ± 0.05 in 1989. They were not statistically different. The mean percentage differences between the simulated and observed seasonal larval totals were 10 ± 3.33 in 1987 and 1988 and 29.8 ± 0.66 in 1989. Independent data sets (i.e. field data in 1989) showed a significant increase in the simulation error of the larval population. Sensitivity analysis indicated that A. sordidatus had a large influence on the population dynamics of L. oregonensis.

In laboratory tests, many miticides affected more than one life stage of the European red mite but most showed greater toxicity to one specific stage. Most were more toxic to nymphs and adults than to eggs. Cyhexatin was more toxic to nymphs whereas fenbutatin-oxide was more toxic to adults than to nymphs. Propargite, formetanate HCl, and dinocap were more toxic to nymphs than to adults. Dicofol and oxythioquinox were more toxic to adults than to nymphs. Dienochlor was the least toxic miticide tested, and was more toxic to nymphs and adults than to eggs. Amitraz, permethrin, and fenpropathrin were repellent to motile stages at low concentrations, but amitraz was also highly ovicidal. Clofentezine and hexythiazox were toxic to eggs and nymphs but not to adults. Affected nymphs developed into the deutochrysalis or teleiochrysalis stages but were unable to eclose from these quiescent stages.

In field trials, applications timed to coincide with a predominance of sensitive stages were successful. Early season applications suppressed mite numbers for much of the growing season. Populations exhibiting considerable synchrony occurred into August suggesting that susceptible stages could be targeted for control throughout the season.

A study was conducted in Butte County of western South Dakota to determine the relationships between habitat characteristics and spatial and temporal changes in community structure of grasshoppers on mixed-grass rangeland. Detrended correspondence analysis (DCA) of 29 undisturbed grasshopper communities and correlation analysis of DCA axis values and habitat variables denned specific spatial gradients underlying the community structure of grasshoppers. Results indicated that grasshopper communities changed along a primary gradient of percentage of coverage of grasses, particularly Buchloe dactyloides (Nutt.) Engelm., and a secondary gradient of percentage composition of clay and sand in the soil.

DCA of 24 grasshopper communities sampled in 1986 and 1987, multiple regression analysis, and factor analysis were used to determine the relationships between specific habitat characteristics and changes in communities of grasshoppers treated with either a nonselective insecticidal spray (malathion) or a selective insecticidal bait (bran bait with carbaryl). Results indicated that between-year change in community composition, or the difference between post-treatment communities in 1986 and 1987, was positively correlated with percentage of coverage of total grasses and forbs. Community malleability, defined as the tendency of a community to return to its predisturbed state, was greater in habitats with high coverages of Agropyron smithii Rydb. and Carex spp., low coverage of Bouteloua gracilis (H.B.K.) Lag. ex Steud., and low species richness of grasses. Our results emphasize the importance of habitat characteristics in structuring undisturbed grasshopper communities and in community change after perturbation with insecticides.

The species of the genus Spilomicrus in America north of Mexico are revised. A generic diagnosis of Spilomicrus, key to genera of Nearctic Spilomicrini, and key to Spilomicrus species in America north of Mexico are given. Four species-groups are defined, viz. distinctus, exul, formosus, and stigmaticalis. Character states, variation, distribution, and relationships of each species are discussed. Twelve of 21 species are recognized as new: S. boweni, S. crassicornis, S. distinctus, S. exul, S. inornatus, S. palustris, S. pumilio, S. robustus, S. sanbornei, S. stepheni, S. superbus, and S. sylvicola. Nine previously known species are redescribed: S. antennatus (Jurine), S. atriclavus Ashmead, S. bifoveatus Kieffer, S. brevicornis (Ashmead), S. flavicornis Ashmead, S. formosus Jansson, S. ruficornis (Provancher), S. stigmaticalis Westwood, and S. virginicus Fouts. The males of S. brevicornis and S. virginicus, as well as the females of S. flavicornis and S. ruficornis, are described for the first time. The following new synonymies are proposed: S. antennatus (= Basalys californica Ashmead), S. atriclavus (= S. foutsi Masner, S. kiefferi Fouts), and S. stigmaticalis (= S. armatus Ashmead).

The effects of Bacillus thuringiensis var. israelensis de Barjac (B.t.i.) on the feeding habits of two black fly predators, Nigronia serricornis (Say) and Acroneuria lycorias (Newman), and a detritivore, Prostoia completa (Walker), were examined. We assessed whether B.t.i.-killed and hot water-killed black fly larvae were less or more desirable to these consumers than live larvae. Nigronia larvae showed no significant differences in predation on larvae within the three categories. Acroneuria nymphs consumed more live than dead prey. Experiments with the detritivore, Prostoia, showed that they preferred dead black fly larvae to live ones. Bacillus thuringiensis var. israelensis treatment may have little direct effect on nontarget organisms, but these studies indicate that there still may be consequences for predators and detritivores when a viable population of larval black flies is transformed into dead organic matter.

The influence of temperature and larval density on the flight performance of Diabrotica virgifera virgifera LeConte was quantified in the laboratory using a tethered flight system. Temperature had a significant influence on trivial flight performance in males and in both young (5 day) and older (25 day) females. The proportion of beetles undertaking trivial flight, and trivial flight duration and frequency peaked at temperatures around 20–25°C. Generally, males were more active than females at lower temperatures. Female beetles did not display sustained flight behavior at 15 or 35°C and males did not undertake sustained flight at 30 or 35°C. Sustained flight duration was unaffected by temperature. Rearing larvae at different densities influenced adult size but had only subtle effects on adult flight performance. Larval density significantly influenced trivial flight duration and frequency of older females and flight frequency of males but had no effect on young females. In general, trivial flight performance peaked when larvae were reared at moderate densities (500–750 per primary rearing container). In young females the propensity for sustained flight, but not flight duration, declined with increasing larval density.

Encapsulation of Bathyplectes curculionis (Thomson) and B. anurus (Thomson) (Hymenoptera: Ichneumonidae) was investigated by dissecting parasitized larvae of three strains of the alfalfa weevil, Hypera postica (Gyllenhal) (Coleoptera: Curculionidae). In laboratory studies, there was no encapsulation of B. curculionis in the western strain of the weevil, a significant level of encapsulation in the eastern strain of the weevil, and nearly complete encapsulation in the Egyptian strain of the weevil. The rickettsia, Wolbachia postica Hsiao and Hsiao, found only in the western strain, was not involved in encapsulation. Variation in encapsulation was due to biological differences between weevil strains. Encapsulation rates among field populations of the western and Egyptian weevils were lower than in the laboratory. Encapsulation rates of weevil populations from zones in which western and Egyptian strains overlap in southern Utah, and between eastern and western strains in Colorado, were intermediate to rates of parental strains. These results imply that B. curculionis effectiveness against the western alfalfa weevil will decline with mixing of weevil strains. Bathyplectes anurus did not evoke encapsulation and was able to develop equally well in all three weevil strains. Our findings illustrate the importance of investigating the compatibility between alfalfa weevil strains and their parasitoids in devising a sound biological control strategy.

The within-plant spatial distribution of Limothrips denticornis Haliday eggs on spring barley (Hordeum vulgare L.) in North Dakota was examined during the growing seasons of 1987 and 1988. In both years, most eggs were found during inflorescence emergence (growth stages 10–10.5 on the Feekes scale), although eggs were detected both prior to and after these growth stages. Once inflorescence emergence was initiated, over 8.5% of the eggs were found in the top two leaf sheaths, with the majority in the flag leaf sheath. Over all barley growth stages, significantly more eggs (P≤0.05) were found in the middle third than in either the top or bottom third of the flag leaf sheath. No difference (P≥0.05) in the within-sheath location of eggs on lower leaves was detected.

The jack pine tip beetle, Conophthorus banksianae McPherson (Coleoptera: Scolytidae), has been distinguished from its sibling species, C. resinosae Hopkins, partly because immature stages were present in the field longer and because it may be bivoltine. A life history study of the tip beetle revealed it is univoitine, overwintering as an adult. The developmental period of C. banksianae from eggs to adults is about the same as that for C. resinosae. As in C. resinosae, adult C. banksianae usually mate in the spring, but some mate the previous fall. Mating occurs on or in the host. Female-biased sex ratios are found consistently throughout the life cycle of C. banksianae and in overwintering adults of C. resinosae. In Ontario, oviposition galleries are initiated in the old shoots until mid-June, thereafter in new shoots. Peak oviposition is completed before new shoots have fully elongated. The very similar life history traits of C. banksianae and C. resinosae suggest the species are closely related, if not the same species as recently proposed.

The feeding behavior of adult Colorado potato beetles has been studied on leaflets from two clones of Solanum berthaultii Hawkes (PI473340, clones #1726 and #1729) and on S. tuberosum L. var. Norchip leaflets treated with leaf extract from S. berthaultii 1726. Treatment of S. tuberosum leaflet with leaf extract from S. berthaultii 1726 (0.075 mg/cm2 of leaflet) did not modify the behavior of adult Colorado potato beetles even if consumption was reduced. On S. berthaultii 1726, consumption and consumption rate were reduced, the frequency of the “moving” behavior increased, the frequency of the “resting” behavior decreased, and the frequency of the “feeding” behavior did not change compared with S. tuberosum. The antifeedant property of S. berthaultii 1726 probably was perceived during the sampling step of the feeding behavior and prevented continuous feeding.

The beetles avoided contact with S. berthaultii 1729 leaflets, less consumption occurred, the frequency of the “feeding” and “resting” behaviors was reduced, and the “moving” frequency increased in most cases. This suggested the presence of deterrents influencing host acceptance and initiation of feeding. On S. berthaultii 1726 and 1729, the frequency of some behaviors changed during the bioassay (2.5 h in duration), probably as a consequence of food deprivation.

A mating suppression bioassay, an electroantennogram study, and a lure attractancy study demonstrated the sensitivity of the Croesia curvalana (Kft.) moth to the female sex pheromone. Mating suppression of 98% was achieved with source concentrations of 30 μg of either (E)- and (Z)-11-tetradecenal (95:5) or the natural pheromone blend of (E)- and (Z)-11-tetradecenal (90:10) + (E)- and (Z)-11-tetradecenyl acetate (85:15) (aldehyde:acetate = 9:1), and was 60% with a source concentration of 0.6 μg. Source concentrations of the minor component acetate, ranging from 15 to 0.6 μg, produced mating suppressions of from 78 to 38%. Male antennae responded to source concentrations of 2 × 10−10 mg (E)- and (Z)-11-tetradecenal (90:10) and antennal saturation occurred at 2 × 10−4 mg. Little female response was found at any age. Polyvinyl chloride lures releasing 1–2 ng/h captured males at approximately the same rate as did virgin moths. Release rates as low as 8 ng/h reduced trap capture from the 4 ng/h release rate found to be most effective under prevailing environmental conditions using Pherocon 1C traps. Results from these studies suggest C. curvalana could be a candidate for pheromone-based field mating suppression.

Early season infestations of adult tuber flea beetles, Epitrix tuberis Gentner, usually are concentrated at the edges of potato fields, and it generally has been assumed that they move into potato fields from the outside inward. This edge-effect suggests that tuber flea beetles overwinter outside potato fields, and other species of flea beetles have been reported to behave similarly (Wolfenbarger 1940; Dominick 1971; Burgess 1981). This may not be true of E. tuberis, however. Hoerner and Gillette (1928), in Colorado, noted that potatoinfesting flea beetles [probably E. cucurneris (Harris), E. subcrinata (Lec.), or E. tuberis] often congregated under piles of old potato vines in potato fields, and Hill and Tate (1942) observed flea beetles feeding on cull tubers in a potato field after harvest. These observations suggest, but do not confirm, that some flea beetles including E. tuberis may remain in harvested potato fields during winter.

The genus Dalbulus (Homoptera: Cicadellidae) consists of 11 species, 10 of which can be found in México (Nault 1990). Some members in the genus, such as the corn leafhopper, Dalbulus maidis (DeLong and Wolcott), and the Mexican corn leafhopper, Dalbulus elimatus (Ball) are serious pests of maize due to their transmission of three corn stunting pathogens: corn stunt spiroplasma (CSS; Spiroplasma kunkelii Whitcomb et al.), maize bushy stunt mycoplasmalike organism (MBSM), and maize rayado fino virus (MRFV) (Nault 1990). Due to the widespread damage that these leafhopper-vectored pathogens cause in maize-growing regions in Latin America, a search for the leafhopper natural enemies was conducted in maize agroecosystems in central México.