Summary
Little is known about the acarofauna associated with wood-boring beetles in Canada, including long-horned beetles (Coleoptera: Cerambycidae). Herein, we assessed the prevalence, abundance, diversity, phenology, and attachment location of mesostigmatic mites (Acari: Mesostigmata) associated with Monochamus scutellatus (Say), and tested whether the abundance and prevalence of mites differed between male and female beetles. A total of 176 beetles were collected in two sites in eastern Ontario in 2008 and 2009 using Lindgren funnel traps baited with α-pinene and ethanol lures, and 71% of hosts had mesostigmatic mites. A total of 2486 mites were collected, representing eight species, four genera, and three families (Digamasellidae, Trematuridae, and Melicharidae). Average prevalence was variable across mite species, and the number of mites per infested beetle also varied across species. Many of the mite species collected in this study have been reported from other cerambycid species, as well as from other wood-boring beetles, such as bark beetles. There was no significant sex bias in the abundance or prevalence of mites between male and female M. scutellatus, which suggests that there is no selective advantage for mites to disperse on females. This study represents the first quantitative investigation of the mites associated with M. scutellatus in Canada.
Methodology
Study sites and sampling design
Wood-boring beetles were sampled in two study sites in eastern Ontario from mid-April to late August in 2008, and from mid-April to early August in 2009. The two study sites were in the boreal shield ecozone in Algonquin Provincial Park (PP): site 1 (S1) (45.902°N, 77.605°W) and site 2 (S2) (45.895°N, 78.071°W). Four Lindgren 12-unit funnel dry traps (Synergy Semiochemicals Corporation, Burnaby, British Columbia, Canada) with four 1 cm3 pest strips (Ortho Home Defense Max, Scotts Company, Marysville, Ohio, United States of America; to kill beetles and mites) and baited with lures, were placed in each site at least 16 m apart, with the collection cups ,80 cm off the ground and at least 2 m from any host trees (distance from trees, trap height, and distance between traps based on Miller and Duerr 2008). Traps were baited with a-pinene and 95% ethanol (released at 2 g/day and 400 mg/day, respectively) lures (Synergy Semiochemicals Corporation, Burnaby, British Columbia, Canada) to attract beetles seeking dead or dying coarse woody debris. Traps were emptied approximately every 2 weeks, trap lures were replaced every 8 weeks, insecticide strips were replaced during each visit to maintain effectiveness, and any mites detached from their host were discarded. Each beetle specimen captured was placed individually into a 2.0 mL microfuge tube with 80% ethanol.
Identifications and mite associations
Cerambycids were identified to species using a dissecting microscope and taxonomic literature (Yanega 1996). The presence, abundance, and attachment location of mesostigmatic mites (hereafter mites) was recorded; other mites (e.g., Prostigmata, Astigmata) were not studied. Prevalence was defined as the percentage of all examined hosts with one or more mites of a given species. Intensity was defined as the number of mites of a given species, carried per beetle with mites (beetles without mites excluded). All mites were removed from the host, cleared in 85% lactic acid for 1–24 hours depending on the degree of opacity, slide-mounted in a polyvinyl alcohol medium and cured on a slide warmer at about 40°C for 3–4 days. Slide-mounted specimens were examined using a compound microscope and identified to species using descriptions from the literature (Hirschmann 1960, 1972; Hurlbutt 1967; McGraw and Farrier 1969). Voucher specimens are deposited in the Canadian National Collection of Insects, Arachnids, and Nematodes, in Ottawa, Canada. Chi-square and Mann–Whitney U tests were performed using SPSS v17 (SPSS Inc., Chicago, United States of America), to assess whether the prevalence or abundance of mites, respectively, diverged significantly between male and female hosts.