Larinus minutus Gyllenhal (Coleoptera: Curculionidae) has been credited with the successful biological control of Centaurea diffusa Lamarck (Asteraceae) in British Columbia, Canada. However, another seed head-feeding weevil agent, Bangasternus fausti Reitter (Coleoptera: Curculionidae), has recently been detected on C. diffusa in British Columbia, and it is unclear how it is interacting with L. minutus. If phenological differences between the two species allow B. fausti to exclude L. minutus from seedheads, and if B. fausti continues to have a low survival rate, populations of C. diffusa may begin to resurge. As a first step in studying the interactions of L. minutus and B. fausti, we compared their phenology and life histories across their known Canadian range and explored the relationship between their abundance and environmental predictors. We quantified adult abundance in the field and collected seed heads from which we reared each species. We found that B. fausti is active earlier than L. minutus, but it is generally found in lower abundance. The abundance of B. fausti had a positive relationship with mean annual precipitation, whereas L. minutus did not have any significant relationship with environmental predictors. Taken together, our study clarifies the life history of B. fausti in Canada in relation to L. minutus. If B. fausti precludes colonisation of seedheads by L. minutus but remains a less effective agent, continued range expansion of B. fausti may reduce the efficacy of C. diffusa biological control.

We evaluated the diversity and spatiotemporal emergence patterns of parasitoid wasp species in the genus Eurytoma Illiger (Hymenoptera: Eurytomidae) associated with leaf galls induced by Diplolepis variabilis Bassett (Hymenoptera: Cynipidae) throughout the Okanagan Valley, British Columbia, Canada. We collected D. variabilis galls throughout the region, recorded adult Eurytoma emergence times, extracted mitochondria DNA from a subset of the emergents, and used cytochrome c oxidase 1 and cytochrome b amplificons to assign sampled individuals to species. We also assayed for the bacterial endosymbiont Wolbachia to evaluate the incidence of thelytoky in Eurytoma. Eurytoma showed an extended emergence period and a significant right skew in male emergence. We recorded six Eurytoma species, one of which appears to be previously undescribed. The greatest diversity of Eurytoma species occurs in the north of the sampled area. Five of the six species showed Wolbachia infection in at least some individuals, and the most abundant and widespread species, Eurytoma imminuta Bugbee, showed high Wolbachia infection levels and an all-female population, which strongly indicates endosymbiont-induced thelytoky. Our results demonstrate that gall communities are locally variable, and we suggest that future studies be undertaken to quantify variation in community composition at more local scales than has been past practice.

Gall wasps in the cynipid genus Diplolepis Geoffroy (Hymenoptera: Cynipidae) attack various species of native and introduced roses in Canada. Although gall forms are diverse, gall wasps are parasitised by highly concordant complexes of parasitoids and inquilines. Many species of gall wasps attack the same host plants and develop over the same periods in the season, suggesting that opportunistic parasitoids may be exploiting a range of hosts rather than specialising. We sampled larvae of Eurytoma Illiger (Hymenoptera: Cynipidae) from galls of D. variabilis (Bassett) and D. rosaefolii (Cockerell), gall inducers that develop fairly synchronously late in the growing season on leaves of Rosa woodsii Lindl. (Rosaceae) in the Okanagan Valley of central British Columbia, Canada. Galls were sampled at five different sites along a gradient from the north end of the valley to the Canada–United States border, a distance of 100 km. We extracted DNA, then amplified and sequenced the cytochrome b segment for each Eurytoma larva. We identified two well-supported clades that were differentiated by neither sampling location nor host. Instead, at least two species of Eurytoma, E. imminuta Bugbee and E. longavena Bugbee, exist at these localities, and both exploit at least two of the Diplolepis hosts found at these sites.

Wolbachia Hertig (Rickettsiales: Rickettsiaceae) is a genus of endosymbionts that are widespread in insects and can have important implications on population dynamics through cytoplasmic incompatibility or sex-ratio distortion. We considered Wolbachia as a possible explanation for female-biased sex ratios often observed in mountain pine beetle populations, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae: Scolytinae), a major pest species in western Canada whose most recent outbreak and range expansion has killed many millions of mature lodgepole pine, Pinus contorta var. latifolia Engelmann (Pinaceae). We used wsp primers to screen for Wolbachia in 10 mountain pine beetle populations with varying degrees of female bias in southeast British Columbia and southwest Alberta, Canada. We found no evidence of Wolbachia in these populations and suggest that other factors may explain the sex-ratio bias.

Galls of Diplolepis variabilis (Bassett) (Hymenoptera:Cynipidae) on their host plant Rosa woodsii Lindley(Rosaceae) support a diverse community of parasitoid and inquiline waspsthat exploit the gall inducer and the gall itself. Here, we studiedquantitative variation in local structure of the gall community in theOkanagan Valley of southern British Columbia, Canada, from the United Statesborder north, to test the hypothesis that dispersal limitation wouldgenerate a distance decay in gall community similarity. We also exploredgall community richness in relation to latitude, as the northern range limitof the gall inducer occurs within our study area. We found that gallcommunities exhibited strikingly similar composition across the studyregion, with most of the major inquilines and parasitoids present across thegall's range. However, the increased richness of rare parasitoid taxa nearthe northern range limits of D. variabilis generated amarginally significant positive relationship between gall community richnessand latitude. Overall, our study suggests that dispersal constraints do notinfluence the composition of the Diplolepis Geoffroy gallcommunity at regional scales, and that gall communities offer useful modelsfor studying the association between community structure and rangelimits.

Stems of Canada thistle (Cirsium arvense (L.) Scop.), with galls of Urophora cardui (L.) at various stages of development, were brushed with a concentrated solution of dimefhoate to kill the gall-inducing larvae. Tissues of untreated and treated galls were compared to study the influence of larvae on each phase of gall growth and development. Galls treated in the initiation phase stopped growing. Galls treated in the growth phase grew slightly, primary nutritive tissue was replaced by a thick layer of proliferating callus, and lignified tissue appeared in its normal location. Galls treated in the maturation phase retained the arrangement of their secondary nutritive tissue but it degraded and callus did not develop in the larval chambers. We concluded that active larvae were necessary for normal gall growth and for the retention of primary nutritive cells, but larvae were not necessary for the formation of lignified tissues or for the retention of secondary nutritive cells.