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.

Carabid beetles were collected using pitfall traps and tree bands in forest stands in southwestern Pennsylvania subjected to defoliation by gypsy moth for the first time. Some of the stands were treated aerially with Bacillus thuringiensis Berliner (B.t.). The guts of all carabids collected were tested for the presence of gypsy moth proteins using the ELISA technique. Twenty-seven of the 33 species (82%) collected from pitfall traps, and four of the seven species (57%) collected under tree bands, tested positive. Of the 1142 individuals from pitfall traps and 73 individuals from tree bands, the percentages positive were 45 and 38%, respectively. Calosoma frigidum Kirby had the highest percentage positive (78%) of any species. Statistically significant differences in percentages positive between B.t.-treated and untreated plots were found only for Pterostichus mutus Say and P. coracinus Newm., and when all species were combined. The presence of nucleopolyhedrosis virus in the gypsy moth population was unanticipated and may have influenced these results through increased feeding on carrion.

Earlier attempts to correlate spruce budworm, Choristoneura fumiferana (Clem.), outbreaks and weather conditions were usually carried out by comparing seasonal data and spruce budworm outbreak development in broad terms: it was found that warm, dry weather favored outbreak development, while cool, wet weather retarded development. In this paper, laboratory experiments and historical data are examined to determine the effect of temperature and precipitation on second-instar larvae, just prior to and after spring emergence. Results tend to show that prolonged rain and freezing temperatures during and shortly after emergence are detrimental and may, in some cases, have a profound impact on outbreak development.

Insects cause considerable loss of seed in white spruce, Picea glauca (Moench) Voss, and Engelmann spruce, P. engelmannii Parry, in British Columbia. The most important species are a maggot, Hylemya anthracina (Cz.), and a seed moth, Laspeyresia youngana (Kit.). Other insects are: a seed chalcid, Megastigmus piceae Roh., a cone axis midge, Dasineura rachiphaga Tripp, a gall midge, D. canadensis Felt, a seed midge, Mayetiola carpophaga Tripp, and a scale-feeding midge. These insects also occur in cones of Sitka spruce, P. sitchensis (Bong.) Carr., and black spruce, P. mariana (Mill.) BSP.

The systemic insecticides dimethoate and formothion proved to be effective against these insects when applied as sprays following pollination in mid-June.

The immature stages of Lexiphanes saponatus (Fabricius) are the first members of Nearctic Cryptocephalinae to be described as well as to be studied. The egg is coated with oblique ornamentations as in other Cryptocephalinae. The larva shows several resemblances with that of the Palearctic genus Suffrianus from which it is distinguished mainly by its large papillate frontal setae. The pupa resembles in general those of Chlamisinae but bears very distinctive projections on the seventh and ninth abdominal segments. The life cycle of L. saponatus is also very interesting. Unlike most other cryptocephaline larvae which live in the leaf litter and are unable to climb on plants, the larva of L. saponatus moves easily on its host plant (Cassandra calyculata) and mimics perfectly the plant buds, becoming almost invisible to the human eye. Although me information is incomplete, it is evident that L. saponatus overwinters in the larval stage, in the first or second instar. It is not known if the larva completes its development during the following warm season or overwinters twice as in other Cryptocephalinae.

A method is described for sampling aquatic insects using black light. Trap design, description of its placement, and conversion to a fumigator is explained. Total numbers of emerging insects captured by aquatic light trap are given and compared with catches in surface and bottom cone traps. Overall effectiveness of the black light trap is discussed.

In all but the flattest terrain, differences in relief produce recurrent and consistent patterns of cloudiness during turbulent or convective weather. The basic patterns consist of fixed patches or lines of low clouds that persist in an otherwise clear sky. But their outlines may even appear in the higher layers of cloud that cross the region during the passage of larger weather systems. Consequently, the areas beneath them experience predictably higher frequencies of cloudiness and rainfall than the terrain outside their borders. Thus their outlines can be used to draw boundaries that separate areas with different climates.

The information above can be used to develop a system of direct observations of changes in local weather that can be applied in several ways during studies of natural populations. Visual methods of observing the weather are always simpler than methods that involve instruments. Where population phenomena are concerned, they also may be more meaningful; and they leave more time free for biological observations. Instruments are essential, however, in any investigation of the properties or requirements of individuals; e.g., in physiological or behavioral studies.

Mites of the family Phytoseiidae, most of which are at least partially predacious, have received considerable attention from fruit entomologists since Parrott et al. (1906, pp. 302-303) stated that they feed extensively on phytophagous mites. This has resulted in much interest in the taxonomic status of Phytoseiidae and several papers on this subject have appeared in recent years.

The feeding habits of nymphs of Perla marginata (Panzer) and Dinocras cephalotes (Curtis) were investigated in the Rio Orbarina (northwestern Italy). These species are among the largest European carnivorous freshwater invertebrates and they play an important role in the trophic structure of small, fishless Apennine streams. We examined the gut contents of 60 P. marginata and 60 D. cephalotes nymphs to characterize the diets and evaluate possible feeding differences between the species. In both of these predaceous stoneflies, the diet included vegetable detritus, mainly in the smaller instars. Both species showed trophic preferences, since only a few taxa constituted most of the ingested prey items, independently of their availability in the substratum. Interestingly, there were no clear differences in prey selection between nymphs of the two species.

Brown larval morphs, diagnostic of Choristoneura occidentalis Freeman, and green larval morphs, diagnostic of C. retiniana (Walsingham), were found on both Douglas-fir and white fir in mixed stands in south-central Oregon. The rank proportion of brown morphs in stands was strongly correlated with the rank proportion of Douglas-fir in host species basal area component. Despite considerable overlap in most phenotypic characters, differences in phenotypic frequencies between sympatric green and brown morphs were found in larval head capsule pigmentation, thoracic shield pigmentation, pupal coloration, and adult forewing ground color. In laboratory matings, neither larval host nor larval color morph influenced the mating success, as assessed by the production of viable eggs. Crosses between females reared from brown larval morphs and males from green morphs produced a slightly lower proportion of viable eggs when compared with intramorph matings. Larval host had little effect on either the fecundity of females or the viability of their progeny. Females reared from brown larval morphs produced significantly more eggs than their green counterparts from the same stand. The occurrence of intermediates in all mixed stands and the production of families with anomalous morph frequencies indicate that these two species hybridize in nature. The lack of much structural differentiation and varying efficacy of reproductive barriers indicate that relatively little differentiation of the regulatory genome has occurred between these two species.

A survey of the phytophagous arthropod fauna of the introduced legume crownvetch, Coronilla varia L., was conducted in Pennsylvania during 1971–73. Samples were taken from large forage fields, highway plantings used for erosion control, and greenhouses. Emphasis was placed on determining what known pests of other forage legumes are associated with crownvetch and on clarifying the relationship of the species to the host plant. Species were categorized as primary, secondary, and incidental according to their intimacy with the host. Biological notes, known host plant range, and association with other legumes are presented for 19 of the 33 primary species. The grasshoppersMelanoplus differentialis (Thomas) and M. femurrubrum (DeGeer) and the gelechiid moth Stomopteryx palpilineella Chambers caused defoliation in several highway plantings. Other abundant species were the alfalfa plant bug, Adelphocoris lineolatus (Goeze); potato leafhopper, Empoasca fabae (Harris); clover stem borer, Languria mozardi (Latreille); and nitidulid beetle Meligethes nigrescens Stephens. The similarity of the phytophagous fauna of crownvetch to that of alfalfa is discussed. Alfalfa pests found not to breed on crownvetch were the meadow spittlebug, pea aphid, alfalfa weevil, clover leaf weevil, clover root curculio, and alfalfa seed chalcid. As yet pest problems on crownvetch are few when compared with those of alfalfa and other forage legumes.

In southwestern Quebec, cereal aphids started to infest cereals in the first week of June, and reached their peak on the second and third weeks of July. There was a significant correlation between the number of alate aphids produced and total number of aphids per colony for R. padi and M. avenae but not for R. maidis. The percentage of alate aphids in colonies of all three species increased as cereals matured. The index of aggregation (b) showed M. avenae was distributed randomly in the field while R. padi and R. maidis were distinctly aggregated.

This paper deals with two sawfly species, Neodiprion americanus banksianae Roh. and N. lecontei (Fitch), important defoliators of pines in eastern North America. It is concerned chiefly with the reactions of the larvae to light and forms part of an investigation of their behaviour in response to physical factors of the environment.

Local dispersal and survival of male spruce budworm, Choristoneura fumiferana (Clem.), moths under field conditions was determined by mark, release, and recapture in pheromone-baited traps. Recapture rates and distance of recapture were dependent upon height of traps and proximity of traps to the release point, but over 65% of those recaptured were caught within 50 m. With traps 20 m apart, 30% of the recaptures were in traps farthest from the release point (50–70 m), a fact which suggests that male spruce budworm may disperse beyond this distance at low densities. Males were recaptured up to 7 days after release, and had a daily survival rate averaging 67%.

Observed and expected frequencies with which fir engraver (Scolytus ventralis) attacks contacted resin blisters or canals in the cortex of white fir (Abies concolor) stems were compared. Cortical regions of the stems were sampled by single bolts sawn from each of 24 firs which had been attacked after felling. Expected frequencies were based on mean proportions of bole surface occupied by the resin structures at attack sites on the bolt. Frequencies were compared on a per-bolt basis and results were combined for χ2 tests. Blister contact (6.5% of attacks sampled) was less than expected (14.0%). Canal contact (17.4%) exceeded the expected (8.2%). Contact frequencies varied directly with percentages of bole surface occupied by the resin structures, and the latter varied significantly among sample bolts. Among-bolt variations in the resin structures were not related to diameters, radial growth rates, or ages of the sections of stem included in the bolts, except that bolts with greater diameters and radial growth rates tended to have lower percentages of bole surface occupied by canals. Almost all beetle attacks that contacted the resin structures failed to produce larval galleries. Results indicate that unless firs are more heavily blistered or canalled than those sampled, the cortical resin system alone is apparently inadequate to protect the trees against the beetles.

Feeding by aphids during 11 days decreased plant weight between 4.7% at an initial density of 5 aphids/plant and 63.9% when the infestation began with 50 aphids/plant. At this infestation level, plant surface area was decreased by 54.3% after 10 days. Both soluble carbohydrate and total protein were reduced by aphid feeding but caloric equivalent of pea tissue was not significantly affected. Extraction by aphids of up to 3.5 cal/plant day was offset by a compensatory increase in production by the plant. Extraction of about 32.7 cal/plant day, equivalent to 0.46 adult aphids/cm2 of plant surface, completely eliminated pea net primary productivity. The relation between energy extracted by aphids, X, and % reduction of plant NPP, Y = 5.54 X−0.058 X2−19.17. Aphid consumption affected pea production directly by removing the amount actually ingested and indirectly because of lost production that would have resulted from the consumed material. Maximum sustainable efficiency of utilization of pea NPP by aphids was between 41% and 47% and maximum sustainable efficiency of transfer of pea NPP to aphid biomass was between 20% and 23%. These high utilization and transfer efficiencies probably would be reduced under field conditions by factors which limit aphid numbers.

Several parasites were surveyed for their ability to develop to pupation in virus-infected hosts. The tachinid Compsilura concinnata (Meigen), the ichneumonids Campoletis sonorensis (Cameron) and Hyposoter exiguae (Viereck), and the braconid Cotesia marginiventris (Cresson) developed to pupation in the armyworm, Pseudaletia unipuncta (Haworth), infected with either the Hawaiian strain of granulosis virus (HGV) or the hypertrophy strain of nuclear polyhedrosis virus (HNPV). The braconid Chelonus insularis Cresson died after its HGV- or HNPV-infected host P. unipuncta died. On the other hand, the braconid Glyptapanteles militaris (Walsh) died in HNPV-infected P. unipuncta before the host died. Some of these parasites had tissues that were melanized and some were encapsulated by the host. The ichneumonid H. exiguae and the braconids Chelonus insularis and Cotesia marginiventris developed to pupation in HGV-infected Spodoptera exigua (Hübner). In some cases, developmental time of parasites in virus-infected hosts was longer than in control hosts.

Small numbers of larval wheat midge, Sitodiplosis mosellana Géhin, survived and matured in each of five field seasons in a plot of spring wheat carrying the Sm1 gene for antibiosis resistance against this insect. Wheat midge developing on resistant wheat had higher survival in the laboratory than in the field, but survival was always very low compared with that of larvae developing on susceptible wheat. The mass of these larvae and their survival during diapause were approximately half those of larvae developing on susceptible wheat in both the laboratory and the field. The survival of some wheat midge larvae on resistant wheat, and their reduced mass, is consistent with the hypothesis that a virulence allele allowing adaptation to Sm1 is present in the population. Assuming this to be the case, the frequency of the allele in the population was estimated to be between 0.8 × 10−4 and 1.6 × 10−2, if surviving larvae are heterozygous for the allele. Although rare, a virulence allele occurring at this frequency would likely allow the wheat midge to overcome the resistance gene Sm1 once resistant wheat is grown over a wide area.

The compatibility of Bacillus thuringiensis (B.t.) with 27 chemical insecticides representing organophosphorus and carbamate insecticides, pyrethrins, chlordimeform, urea derivative, and antifeedant were studied by way of their effects on germination of the bacterial spores, replication of vegetative cells and spore staining, and refractive index characteristics.

The results showed that: (1) Carbamates were generally more compatible with Bacillus thuringiensis than were the other insecticide groups tested. (2) Technical formulations were less harmful to the bacteria than wettable powders which were less harmful than emulsifiable concentrates. (3) Of the 27 pesticides, those most compatible with B.t. were Orthene®, Dylox®, Lannate®, Sevin®, Zectran®, and Dimilin®. These insecticides are considered recommendable for use in integrated control operations with Bacillus thuringiensis if the target insects are susceptible to them and provided that due regard is given to the environmental implications of their use.

Before atten~pting to determine the nutritional requirements of Rhodnius prelixus Stål, a blood-feeding reduviid bug, it was necessary to build a feeding apparatus that would permit the insects to feed normally on various artificial diets. Since it was expected that large numbers of animals would have to be fed individually, practical considerations demanded that the feeding apparatus be easy to service and maintain. Some of the experimental diets would be extremely expensive and radioactive and consequently an apparatus that would permit the use of small volumes of diet was required.