The Canadian species of the genus Placusa Erichson are reviewed. Eight species are recorded, of which four constitute new Canadian records (P. despecta Erichson, P. incompleta Sjöberg, P. petulans Casey, and P. vaga Casey) and two are new to science (P. pseudosuecica Klimaszewski sp.nov., and P. canadensis Klimaszewski sp.nov.). Placusa turbata Casey, one of the two species previously recorded from British Columbia, is here considered a synonym of P. tachyporoides (Waltl) and is reported for the first time from eastern Canada (New Brunswick, Ontario, Quebec). New data are provided on the systematics, distribution, bionomics, and relationships of selected North American species. A key to the species occurring in Canada is presented with illustrations of the median lobe of the aedeagus, spermatheca, male tergite 8, antennae, and outline drawings of the head and adult forebody for each species. Selected Palearctic species are also illustrated for easy comparison with the closely related Nearctic species. The Canadian distribution is presented on contour maps, and world distribution is discussed for all species. The following lectotypes are designated for the Nearctic species which were described from more than one specimen without former holotype designation: Casey (1893, 1911): P. frosti, P. strata, P. tacomae, P. turbata; Erichson (1840): P. despecta; and Sachse (1852): Oxypoda minuta Sachse. Oxypoda minuta is transferred to the genus Placusa and newly synonymized with P. despecta Erichson (1840).

Five species of Trichomalopsis Crawford associated with Haematobia irritans (L.) (horn fly), Musca domestica L. (house fly), Musca autumnalis DeGeer (face fly), and Stomoxys calcitrans (L.) (stable fly) in North America are reviewed. The species Trichomalopsis americana (Gahan), Trichomalopsis dubia (Ashmead), Trichomalopsis sarcophagae (Gahan), Trichomalopsis tachinae (Gahan), and Trichomalopsis viridescens (Walsh) are described, keyed, and differentiated from other recognized North American species. Lectotypes are designated for T. dubia, T. sarcophagae, and T. tachinae. Distribution and host associations are recorded for the species. Trichomalopsis americana and T. viridescens are newly recorded as parasitoids of M. domestica; T. dubia and T. sarcophagae are also newly recorded as parasitoids of Hypoderma lineatum (Villers) (common cattle grub) and Hypoderma bovis (L.) (northern cattle grub), respectively. Some previously published host associations and parasitoid identifications are corrected based on examination of voucher specimens. The known biology of each species is reviewed. The presence of Trichomalopsis albipilosa (Gahan) in North America is considered to be erroneous based on a misidentification of T. americana.

The species Phtheiropoios centralissp.nov. is described and illustrated from specimens collected on an undescribed species of Ctenomys from Rio Quinto, central Córdoba Province, Argentina. Diagnostic features for the new species include proportion of the male forficula, male external genitalia, and counts of setae and body measurements in both sexes. Its morphological affinities with other species and a key to males of all species of the genus Phtheiropoios known to parasitize rodents of the genus Ctenomys are included.

The occurrence and distribution of resistance to insecticides in populations of the obliquebanded leafroller, Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae), from apple, Malus × domestica Borkhauser (Rosaceae), and pear, Pyrus communis L. (Rosaceae), orchards in the various production areas of southern Ontario were assessed in the laboratory and field from 1993 to 1999. Laboratory bioassays were conducted with neonate larvae from the first laboratory generation. Responses of populations from commercial orchards where control failures had occurred or where populations were large or damaging were compared with populations from unsprayed wild hosts. Resistance to azinphosmethyl and to pyrethroids and methomyl was identified in populations from all areas. Resistance levels ranged from 4- to 27-fold for azinphosmethyl, 4- to 8-fold for cypermethrin (a representative pyrethroid), and 3- to 5-fold for methomyl. In the field, deltamethrin was more effective than azinphosmethyl against a population resistant to both insecticides. Resistance to azinphosmethyl was unstable and rapidly declined in a population newly established in the laboratory and not selected with azinphosmethyl. After selection for nine generations, resistance declined only slowly when selection pressure was removed for four generations. This instability may be exploited in the management of resistance, but the possible cross-resistance between azinphosmethyl and pyrethroids needs clarification.

A key stage in the development of an insect epizootic, either natural or induced, is the transmission of a pathogen from an infected to an uninfected host (Andreadis 1987). The establishment of secondary infections can augment long-term control by increasing the amount of inoculum present within the environment (Thomas et al. 1995). The ease of disease transmission from an infected to a healthy host is an important consideration in evaluating the potential of an entomopathogen as a microbial control agent. Currently, we are field-testing the entomopathogenic fungus Beauveria bassiana (Balsamo) Vuillemin (Moniliaceae), for the suppression of adult western corn rootworm, Diabrotica virgifera virgifera LeConte, which is a key pest of corn, Zea mays L. (Gramineae), throughout the north-central United States and eastern Canada (Mulock and Chandler 2000). During our investigations we have often observed sporulating cadavers on corn plants, particularly within the leaf collars, following fungal application. In this study, we estimated the effect of the density of infected cadavers and the length of exposure time on disease transmission in adult western corn rootworm.

The influence of male and female body size on copulation duration and probability of insemination was determined for Anthocoris whitei Reuter allowed to mate at two temperatures. Copulation duration decreased significantly with increasing male length or increasing relative size (male length divided by female length). Female length had no effect on copulation duration. We interrupted copulation at 20 or 40 min at both 25 and 15 °C to determine the interacting effects of male size, temperature, and copulation duration on probability of insemination. Insemination probabilities increased with increasing male size, increasing temperature, and increased duration of copulation. Large males were more successful than small males at inseminating females at cool temperatures and for severely shortened copulations. Results are consistent with the hypothesis that males of this species experience physical difficulties either in achieving intromission or in forcing sperm through the aedeagus, and that larger body size in males lessens these difficulties.

The poplar and willow borer, Cryptorhynchus lapathi (L.), known to be present in British Columbia since 1923, primarily attacks species of Salix L. (Salicaceae) and Populus L. (Salicaceae). Larvae bore into stems, causing them to break easily. The impact of the weevil has been rising in recent years because of the increasing importance of poplar and willow from both economic and ecological perspectives. We conducted a study at 45 locations in British Columbia to determine host use among native Salix spp. and the between- and within-tree dynamics of C. lapathi. There were 11 new host records, but the incidence of attack was similar among species. Attacked trees were larger in general and had more dead wood and stems, more adventitious branches per stem, more total breaks per stem, and more naturally caused breaks per stem than their attack-free neighbours. Breaks caused by C. lapathi tended to be slightly larger in diameter and lower on the stem than naturally caused breaks. Bases of stems were preferentially attacked, and C. lapathi selected large stems in which to oviposit. As large attack-free trees become less abundant, weevils apparently start to attack small-diameter stems. Although C. lapathi is adversely affecting the health of willows in British Columbia, there is no evidence that any Salix species is threatened by weevil-caused extinction.

Callow adults of the pine shoot beetle, Tomicus piniperda L., were fed shoots of Scots pine, Pinus sylvestris L. (Pinaceae), to investigate the influences of shoot age and feeding duration on survival and weight of callow adults and to characterize the relationship between the volume of shoot tissue excavated and weight gain. Heavier callow adults had better survival than lighter ones, and survival was higher on current-year shoots than on 1-year-old shoots. A significant relationship was observed between the amount of tissue excavated by callow females on current-year shoots and their body weight gain, a trend not observed in callow males. These results suggest that beetle weight and survival may be reduced when availability of current-year shoots during maturation feeding is limited because of competition (i.e., during population outbreaks), thus negatively affecting the production of future generations.

Eighteen parasitoid species were found associated with obliquebanded leafroller, Choristoneura rosaceana (Harris), and three-lined leafroller, Pandemis limitata Robinson, from 1982 to 1984, on apple and other host plants in the southern interior of British Columbia. The leafroller parasitoids included a Glypta Gravenhorst species (Hymenoptera: Ichneumonidae), Diadegma eureka (Ashmead) and Diadegma interruptum pterophorae (Ashmead) (Hymenoptera: Ichneumonidae), and Hemisturmia tortricis (Coquillett) (Diptera: Tachinidae). The two leafroller species were found on 18 wild host plants from 10 plant families.

The European apple sawfly, Hoplocampa testudinea (Klug), is a pest of apple, Malus pumila Bork. (Rosaceae), in orchards. Introduced from Europe onto Long Island, New York, in 1939, it gradually invaded the New England states (Pyenson 1943). Downes and Andison (1942) also reported the apple sawfly on Vancouver Island in 1940. In 1979, H. testudinea was discovered for the first time in southern Quebec (Paradis 1980), after which it spread throughout the apple-growing areas of this province (Vincent and Mailloux 1988). There are no published records on any natural enemies of H. testudinea in North America.

The balsam twig aphid, Mindarus abietinus Koch, is a major pest of balsam fir, Abies balsamea (L.) Mill. (Pinaceae), grown as Christmas trees in eastern Canada and the United States (Nettleton and Hain 1982; Kleintjes 1997). This aphid has three or four generations from April to July, and overwinters as eggs on fir shoots. Mature fundatrices deposit progeny on new shoots in late May. Infested shoots develop into pseudogalls characterised by stunting and needle distortion, thus reducing the aesthetic value of trees.