Trigonopeltastes thomasi sp.nov. from Sumidero Canyon National Park, Chiapas, Mexico, is described and figured. Unusual characters of the new species that relate to generic placement are discussed.

In a survey of predaceous phytoseiid mites from 65 apple blocks in the Hood River Valley, Oregon, Metaseiulus occidentalis (Nesbitt) and Typhlodromus pyri Scheuten were the principal species present. Metaseiulus occidentalis predominated over T. pyri by a ratio of about 2:1 in 1984 mites collected during 1985. In experimental, commercial, and integrated pest management blocks, M. occidentalis was present alone or predominated over T. pyri in up to 88% of the blocks, whereas T. pyri occurred alone or predominated in up to 20% of the blocks. Both species occurred in near equal proportions in a maximum of 20% of blocks. An analysis of nine factors influencing the relative abundance of M. occidentalis and T. pyri indicated that vegetation in the habitat surrounding the block and the pesticides used were most important. In 1986, seasonal distributions and proportions of predatory mites found in individual blocks were similar to those found in 1985. The feasibility of managing mixed populations of T. pyri and M. occidentalis in Hood River orchards is discussed.

A new species, Colias johanseni, is described. This species has male androconia similar to Colias meadii Edwards, 1871, and many palaearctic, neotropical, and ethiopian species, but the wing pattern is generally similar to that of Colias hecla Lefèbvre, 1836. Thus far, it has been found only on dry tundra at Bernard Harbour, N.W.T., Canada.

Controlled field studies carried out in plots within a field of NorMan flax, Linum usitatissum L., showed that the loss of flax plants caused by the red-backed cutworm was proportional to the number of cutworm larvae present. A density of 16 larvae per 0.5 m2 destroyed most plants by severing the plant stems at the soil surface. The loss of only some plants at larval densities lower than 16 larvae per 0.5 m2 resulted in a small but significant increase in per plant yield but the increase did not completely compensate for the yield reductions caused by plant loss. The larvae removed plants in blocks with the result that the density of the remaining plants was unchanged and the opportunity for compensating plant growth was limited. An equation defining this relationship between larval densities and yield is presented. Ancillary experiments in which the population of cutworm larvae was sequentially sampled showed that, after an initial loss of about 20% when the plots were established in the field, the larval population remained constant. The proportion of the larvae found around damaged plants also remained constant until the larvae became immobile through preparation for pupation. Because of this stable relationship, reliable estimates of potential crop loss from cutworm larvae in flax should be possible by sampling for cutworms only around damaged plants within a specified row length.

Five species of Limnoporus Stål (L. canaliculatus [Say], L. dissortis [Drake and Harris], L. nearcticus [Kelton], L. notabilis [Drake and Hottes], and L. rufoscutellatus [Latreille]) were each sampled at 20 electrophoretic loci. Twofold differences among species in mean heterozygosity appear to be unrelated to presence of wing dimorphism. Low heterozygosity in some populations within species may reflect geographic isolation. There were substantial differences in allele frequency among, but not within, species. Limnoporus rufoscutellatus from western Europe and L. nearcticus from Alaska were the most similar pair of species, with a Nei’s standard genetic identity that is generally found only between populations of the same species. Limnoporus canaliculatus was the most divergent species, and the relationship among L. dissortis, L. notabilis, and the L. rufoscutellatus – L. nearcticus pair is resolved as a trichotomy.

A mark–recapture study examined Trypodendron lineatum (Olivier) spring flight dispersal in a coastal forested valley in British Columbia. Pheromone-baited traps were placed throughout the valley in five separate experiments. Recapture patterns of marked beetles were related to weather, topography, vegetative cover, and source of attractants.

Wind direction within the forest setting, 350 m from the closest open site, was quite variable with a beetle recapture pattern mat was non-directional. At a forest setting less than 50 m from an open site and road, diurnal up-valley winds resulted in an upwind beetle recapture pattern at 25 m from the release site. Beetles were recaptured at distances as far as 1.9 km downwind and 1 km upwind from the release site. Most beetles were recaptured within 2 h of release at distances up to 50 m. In traps at distances of 350–700 m, similar numbers of beetles were recaptured on the day of release as were recaptured during the following week. At distances greater than 1 km, almost all beetles took longer than 1 day to be recaptured.

Adult corn rootworm beetles, Diabrotica virgifera virgifera LeConte, were maintained at five fluctuating temperature regimens with daily average temperatures of 16.0, 19.5, 23.0, 26.5, and 30.0°C. The mean number of eggs laid per female was greatest (602) at 26.5°C and least (295) at 16.0°C. The median length of life decreased with increasing temperature from 13.8 weeks at 19.5°C to 7.9 weeks at 30.0°C. Parameters were estimated for nonlinear functions relating age-specific fecundity and age-specific survival to physiological age.

Experiments were conducted using balsam fir twigs treated with Bacillus thuringiensis Berliner to examine the influence of temperature and exposure time on mortality of spruce budworm, Choristoneura fumiferana Clemens. Twigs were sprayed with a commercial formulation (8.4 BIU/L) using droplets of 40–70 μm diameter at densities, ranging from 0.5 to 5.5 droplets per needle. Temperature affected progression but not the level of cumulative mortality during 14 days of feeding on sprayed foliage. The LT50 decreased from 12–17 days at 13°C to 2–4 days at 25°C, depending on droplet density. Temperature between 13 and 25°C had a limited effect on dose acquisition because 40–60% of the larvae were able to acquire a lethal dose within 1 day of feeding on foliage with 0.5–1.5 droplets per needle, regardless of temperature. Under these conditions dose acquisition was not limited by temperature-dependent consumption of foliage, but rather by feeding inhibition associated with the dose initially ingested. This also limited the influence of exposure time; a 7- or 14-fold increase in exposure time increased larval mortality at most by 25%. Implications of these findings for improving efficacy of B. thuringiensis in forestry applications are discussed.

Larvae of Arrenurus bartonensis Cook, Arrenurus birgei Marshall, Arrenurus neobirgei Cook, and Arrenurus rotundus Marshall are described for the first time. Larvae of A. rotundus can be distinguished reliably from the other three by differences in morphology. Larvae of A. bartonensis, A. birgei, and A. neobirgei are very similar, but can be separated by comparing shape and size of the excretory pore plate, and by measurements of the dorsal plate and the tarsus of the third leg.

Two exotic species of Xyleborus (Coleoptera: Scolytidae) of Asian origin have recently been detected in the United States. Xyleborus pelliculosus Eichhoff has been collected in Pennsylvania and Maryland, and X. atratus Eichhoff from Tennessee, Georgia, Maryland, Virginia, and West Virginia. Descriptions of both species and a revised, illustrated key to members of the genus Xyleborus in eastern North America are presented. An explanation is proposed for the large numbers of recent introductions of exotic ambrosia beetles from eastern Asia into eastern North America.

Cymodusa borealis sp.nov. (Hymenoptera: Ichneumonidae) is described from the Canadian arctic. This species belongs to the cruentata group of Cymodusa Holmgren (sensu Sanborne 1986).

Sinophorus wushensis sp.nov. (Hymenoptera: Ichneumonidae) is described from Taiwan. This is the first verified record of Sinophorus from Taiwan.

A non-pest population of Colorado potato beetle, Leptinotarsa decemlineata (Say), was monitored in the field and in the laboratory to define some cultural and host plant factors that might prompt increased use of potato by a population locally adapted to a wild host species (Solanum sarrachoides Sendt.). This study tested whether elimination of the beetle’s natural host from plots of potato would result in increased densities of beetles on potato, and examined whether beetles showed differences in performance on and in preference for S. sarrachoides or potato. In 2 years of study, egg densities on potato were higher in weed-free than weedy plots; paired preference tests in the laboratory also indicated that beetles deposited the most egg masses (92%) on S. sarrachoides. Densities of larvae and adults on potato were not affected by weed density. Growth rates of larvae were significantly faster on S. sarrachoides than on potato for both early-season (pre 7 July) and late-season (post 21 July) foliage. Survival and adult size were not affected by host species. In choice tests, late-instar larvae preferred S. sarrachoides to potato. Host preference of larvae varied with age of foliage, and S. sarrachoides became increasingly preferred later in the growing season.

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.

The Nearctic species of the subgenus Anomophagus Reitter of the genus Rhizophagus Herbst are revised. Four taxa are recognized: R. brunneus brunneus Horn 1879, R. brunneus fenyesi Méquignon 1913a, R. pseudobrunneus sp.nov., and R. galbus sp.nov.

For the other Nearctic species of the genus, a diagnosis, a type material section, and distributional notes are provided. Two new taxa are described, R. minutus rotundicollis and R. pusillus. Seven specific names are treated as new junior synonyms, namely (with the valid name in parentheses): R. longiceps Casey 1916 and R. rectus Casey 1916 (= R. cylindricus LeConte 1866); R. minutus quadriguttatus Méquignon 1913b (= R. minutus minutus Mmnerheim 1853); R. remotus luteus Méquignon 1913b (= R. remotus LeConte 1866); R. sculpturatus horni Méquignon 1913b (= R. sculpturatus Mannerheim 1852); R. dimidiatus testaceus Méquignon 1913b and R. dimidiatus assimilis Méquignon 1913b (= R. dimidiatus Mannerheim 1843). The subgenera name Syringobidia Casey 1916 (type species: R. cylindricus LeConte 1866) is treated as a new junior subjective synonym of Rhizophagus s.str. A key to all Nearctic species of Rhizophagus is provided with distribution maps of the species.

Centroptilum infrequens McDunnough, 1924 was found to be widespread in Canada and was described in detail at the 5th International Ephemeroptera Conference, Marysville, Australia, 1987 (Lowen and Flannagan 1989). At that time, similarities between C. infrequens and published accounts of Pseudocentroptilum pennulatum (Eaton 1870) were noted and it was suggested that these species are conspecific. We have recently compared specimens of C. infrequens with specimens of P. pennulatum from western Europe, and have noted no discernable differences at any life stage. We therefore conclude that Centroptilum infrequens McDumough, 1924 is a junior synonym of Pseudocentroptilum pennulatum (Eaton) 1870. This is the first record of Pseudocentroptilum in North America and the first record of a holarctic Pseudocentroptilum species, as P. pennulatum is also known from the arctic Ural and Pacific Coast regions of the Soviet Union.

The Colorado potato beetle is a major worldwide pest of potato and several other solanaceous plants. Insecticidal resistance is a serious problem in the northeastern and mid-Atlantic regions of the United States and a developing problem in other potato production areas of the United States and Canada (Forgash 1985; Johnson and Sandvol 1986; Boiteau et al. 1987). In the northwestern United States, insecticides applied to control the green peach aphid also control Colorado potato beetle, but these insecticides are likely to become ineffective due to the development of resistance or unavailable because of restricted use and environmental concerns. Biologically based management strategies are needed to reduce dependency on insecticides; these strategies require new basic knowledge including understanding prolonged diapause in populations of the Colorado potato beetle. Krysan et al. (1986) established that the occurrence of prolonged or repeated diapause can influence management strategies for insects, especially with respect to crop rotation.