Too much work, not enough tarsi: group size influences Bombus impatiens (Hymenoptera: Apidae) worker reproduction with implications for sublethal pesticide toxicity assessments.

As bumble bees may routinely forage on pesticide-treated plants, it is imperative to apply pesticides that pose minimal risk. Identifying such reduced-risk pesticides requires toxicity tests using biologically relevant and standardized exposure methods. Our goal was to develop a functional and reliable queen-less micro-colony method for determining the sublethal effects of pesticides on Bombus impatiens Cresson, a species for which further toxicity assessments are needed. Originally developed using Bombus terrestris (L.), this method involves isolating three workers and allowing them to establish and maintain a colony. The workers and brood can then be exposed to pesticides and various effects measured simultaneously. Our preliminary work indicated that B. impatiens workers were unable to reproduce under the micro-colony conditions developed for B. terrestris. In the current study, we focused on the potential role of group size in B. impatiens worker reproduction by placing groups of three or five sister workers together and assessing their ability to establish a colony and rear males to adulthood. While both groups oviposited and produced males, significantly more males emerged from micro-colonies of five workers. We conclude that group size affects B. impatiens worker reproduction, and this effect in bumble bees varies interspecifically. In the context of toxicity testing, we recommend the use of at least five B. impatiens workers in micro-colonies to ensure a level of reproduction that allows the detection of potential sublethal changes to reproduction or development.

Impact of currently used or potentially useful insecticides for canola agroecosystems on Bombus impatiens (Hymenoptera: Apidae), Megachile rotundata (Hymentoptera: Megachilidae), and Osmia lignaria (Hymenoptera: Megachilidae).

Pest management practices may be contributing to a decline in wild bee populations in or near canola (Brassica napus L.) agroecosystems. The objective of this study was to investigate the direct contact toxicity of five technical grade insecticides--imidacloprid, clothianidin, deltamethrin, spinosad, and novaluron--currently used, or with potential for use in canola integrated pest management on bees that may forage in canola: common eastern bumble bees [Bombus impatiens (Cresson); hereafter bumble bees], alfalfa leafcutting bees [Megachile rotundata (F.)], and Osmia lignaria Cresson. Clothianidin and to a lesser extent imidacloprid were highly toxic to all three species, deltamethrin and spinosad were intermediate in toxicity, and novaluron was nontoxic. Bumble bees were generally more tolerant to the direct contact applications > O. lignaria > leafcutting bees. However, differences in relative toxicities between the three species were not consistent, e.g., whereas clothianidin was only 4.9 and 1.3x more toxic, deltamethrin was 53 and 68x more toxic to leafcutting bees than to bumble bees and O. lignaria, respectively. Laboratory assessment of direct contact toxicity, although useful, is only one measure of potential impact, and mortality under field conditions may differ greatly depending on management practices. Research conducted using only honey bees as the indicator species may not adequately reflect the risk posed by insecticides to wild bees because of their unique biology and differential susceptibility. Research programs focused on determining nontarget impact on pollinators should be expanded to include not only the honey bee but also wild bee species representative of the agricultural system under investigation.

Evaluation of sampling methodology for determining the population dynamics of onion thrips (Thysanoptera: Thripidae) in Ontario onion fields.

Onion thrips, Thrips tabaci Lindeman, are an economic pest of alliums worldwide. In Ontario onion-growing regions, seasonal abundance and population trends of onion thrips are not well known. The objectives of this research were to investigate onion thrips population dynamics by using both white sticky traps and plant counts, to gain insight into flight height, and to determine the genus and sex of thrips fauna present in monitored fields. Adult thrips were captured on white sticky traps placed in two commercial onion fields in the Thedford-Grand Bend Marsh region as early as mid-May in 2001, 2002, and 2003. Thrips were not recorded on onion plants in these fields until late June and early July. A comparison of sticky trap captures to plant counts revealed a strong, positive correlation, indicating that sticky traps, which consistently detected thrips earlier than plant counts, could be used instead of plant counts early in the season to monitor onion thrips populations. Pole traps placed in onion and an adjacent soybean, Glycine max (L.) Merr., field revealed that regardless of crop type, most thrips were captured 0.7-0.95 m above the soil surface. During this study, 70% of 137,000 thrips captured on sticky traps and 89% of 1,482 thrips captured in pan traps were female onion thrips. No male onion thrips were identified in this study: most of the remaining thrips were Frankliniella spp.

Resistance to Acarapis woodi by honey bees (Hymenoptera: Apidae): divergent selection and evaluation of selection progress.

Two generations of honey bees, Apis mellifera L., selected for resistance to tracheal mites, Acarapis woodi (Rennie), were produced from a foundation stock. The mite resistant lines had significantly low mite abundances and prevalences in each selected generation. The high mite-resistant lines of the first selected generation showed resistance equal to that of bees that had undergone natural selection from tracheal mite infestations for 3 yr in New York. Additionally, the high mite-resistant lines of the second selected generation and Buckfast bees had significantly lower mite abundances and prevalences than honey bees from control colonies which had never been exposed to tracheal mite infestation in Ontario. These results corroborate studies that have shown that honey bees possess genetic components for tracheal mite resistance that can be readily enhanced in a breeding program. The two methods used for evaluating relative resistance of honey bees to tracheal mites, a short-term bioassay and evaluation in field colonies, were positively correlated (rs = 0.64, P < 0.001).

Qualitative and quantitative analyses of volatiles and pheromone gland extracts collected fromGalleria mellonella (L.) (Lepidoptera: Pyralidae).

Chemical analyses of pheromone-gland extracts and volatiles released by maleGalleria mellonella (L.), the greater wax moth, resulted in the identification and quantification of the aldehydes, primary alcohols, and fatty acids of nonane and undecane. Adult females released none of these six compounds. Mean percentages of the aldehydes and alcohols in the gland extracts were 19.0% undecanal, 3.9% nonanal, 48.3% 1-undecanol, and 28.8% 1-nonanol. Mean percentages of the aldehydes and alcohols in volatiles collected during the first hour of scotophase from moths 1 to 9 days old were 77.4% undecanal, 20.8% nonanal, 1.46% 1-undecanol, and 0.36% 1-nonanol. Age did not significantly affect the amount of each compound collected. The collection of volatiles from moths 3 to 5 days old during a 12-hr scotophase indicated that production was greatest during the first and third quarters of the period. Methylation of group volatile samples allowed the quantification of the fatty acids.