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The parathalassine genera Thalassophorus Saigusa, Eothalassius Shamshev and Grootaert, and Chimerothalassius Shamshev and Grootaert are recorded from the New World for the first time. Thalassophorus arnaudi Brooks and Cumming sp. nov. is described from specimens collected at coastal localities in British Columbia, Oregon, and California, and represents the second known species in the genus, the type species being T. spinipennis Saigusa, known only from Rishiri Island in Hokkaido Prefecture, Japan. Detailed illustrations of the male genitalia of T. spinipennis are provided. Eothalassius borkenti Cumming and Brooks sp. nov. is described from specimens collected along the Pacific coast of Costa Rica, bringing the total number of described species of this former Southeast Asian genus to three, with one probable additional described species in the Mediterranean region. The genus Chimerothalassius, which was previously known from a single New Zealand species, is recorded from the island of Dominica, based on a female specimen plus a slide-mounted wing of an undescribed species. A new undescribed parathalassiine genus is also recorded from Chile, based on limited material of two undescribed species. A key to the six genera of Parathalassiinae in the New World, including Parathalassius Mik and Microphorella Becker, is given, as are some preliminary remarks on the limits and phylogenetic relationships of the parathalassiine genera.
We present evidence favoring the use of (E)-pityol as an aggregation pheromone in Pityophthorus pubescens (Marsham). (E)-Pityol was detected in effluvia of male and female P. pubescens, and antennae of both sexes responded to (E)-( )-pityol in electroantennogram assays. In two-choice olfactometer tests, males significantly preferred (E)-( )-pityol and (E)-(±)-pityol to blank controls at doses of 1, 10, and 100 ng, whereas females only showed a preference for (E)-pityol at the 1 ng dose.
We examined rates of late-season parasitism of larvae of the wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), by native species of Bracon F. (Hymenoptera: Braconidae) over 8 years in Montana and North Dakota, United States of America. We found that rates of parasitism of larvae in diapause chambers reached a maximum of 46%, exceeding the previously reported maximum of 2.5% in 75% of sites and years examined. In contrast to previous work, our results demonstrate that C. cinctus larvae are suitable hosts for braconid parasitoids, even after the formation of diapause chambers, and suggest that parasitism rates may be underestimated if stems are sampled prior to harvest.
Although human-modified landscapes are characterized by the loss of natural habitats, new habitats also can be created and exploited by many species. The importance of landscape change to invertebrate associations (particularly host-parasite associations) is under-studied. Our objective was to determine whether prevalence and intensity of gregarine parasitism in the damselfly Ischnura verticalis (Say) (Odonata: Coenagrionidae) differed between 17 artificial and 7 natural wetlands in landscapes that varied in amount of forest and wetland cover and road density determined at spatial extents of 500 m and 1 km from each wetland. Wetlands were located in and around Ottawa, Ontario, and Gatineau, Quebec, Canada. Wetland type did not account for significant variation in principal components based on forest and wetland cover and road density at either spatial extent. Gregarine prevalence was higher in damselflies collected from natural wetlands than in those collected from artificial wetlands and was positively associated with increasing forest cover. In contrast, gregarine intensity was inversely related to road density. Our results suggest that parasitism of damselflies by gregarines is associated with wetland type and landscape characteristics, although the mechanisms producing such relationships are unknown.
Biodiversity & Evolution/Biodiversité et evolution
The demise of the American bison, Bison bison (L.), following European settlement has given rise to two hypotheses regarding the fate of their dung-associated insects. The “extant” hypothesis proposes that all of these taxa now persist in the dung of cattle, Bos taurus L. The “extinction” hypothesis proposes that a subset of these taxa were unable to make this transition and have gone extinct. We examined these hypotheses by comparing the response of coprophilous insects to dung of bison versus cattle on similar diets and versus dung of cattle on different diets. Results showed insects to be more responsive to changes in diet than to changes in host species and, therefore, were supportive of the extant hypothesis. To our knowledge, these data provide the first experimental comparisons of bison dung versus cattle dung as habitat for coprophilous insects.
Little research has addressed the impacts of invasive-species establishment on native forest insect communities. Such information is lacking even for gypsy moth, Lymantria dispar (L.) (Lepidoptera: Erebidae), the most thoroughly studied invasive forest insect. We investigated the ecological impacts of gypsy moth on native species at sites in north-central Ontario, Canada, with and without significant histories of gypsy moth defoliation over a 2-year period. Patterns in native forest caterpillar communities are described using measures of species diversity and multivariate analysis. We documented a transition from low-level to dominant gypsy moth populations. Sites with different gypsy moth outbreak histories exhibited differences in rank-abundance distributions and dominance structures in the first year of the study; by the second year, gypsy moth was dominant at sites of both types irrespective of their previous defoliation history. Contrary to our predictions, we found that gypsy moth outbreak history had no significant effects on native caterpillar community diversity or structure. However, sites with currently high gypsy moth abundance demonstrated significant shifts in late-season caterpillar community structure. Our results suggest that observed community differences were due to the presence of a highly abundant folivore, and not to permanent shifts in the native community because of the introduction of an invasive species.
The efficacy of pitfall traps baited with pheromone and cereal oil in capturing Tribolium confusum Jacquelin du Val and T. castaneum (Herbst) (Coleoptera: Tenebrionidae) was low (trap catch) in mill and simulated warehouse settings. In a simulated warehouse experiment, strains of Tribolium Macleay recently taken from mills were caught 24% less often in traps than were laboratory strains, and T. confusum was caught 40% less often than T. castaneum. Both species were found together in all flour samples taken from a Canadian flour mill. A comparison of the species ratio in flour samples with that found in traps revealed that T. confusum was caught less often in traps than was T. castaneum. In flour, T. castaneum burrowed more than did T. confusum, and there were differences in burrowing behaviour between the four T. castaneum strains. Mills infested with T. confusum may have higher levels of infestation than was previously thought, indicating that further research into beetle behaviour in mills is needed.
Little is known about the associations of ants (Hymenoptera: Formicidae) with subterranean aphids and mealybugs (Hemiptera: Sternorrhyncha: Aphididae and Pseudococcidae), particularly in Canadian grasslands. Knowledge of host plants for these sternorrhynchans is equally rare. We carried out a plant-based survey of ants and belowground aphids and mealybugs in a native fescue grassland in east-central Alberta, Canada. We found 23 species of ants, 12 of which (species of Lasius F., Myrmica Latreille, Tapinoma Förster, and Temnothorax Mayr) were in association with subterranean sternorrhynchans. Twelve species of aphids and mealybugs were collected; 3 are new records for Canada and 2 are possibly undescribed. Most ant species associated with sternorrhynchans were found with more than one species of sternorrhynchan, sometimes in the same nest. Almost all sternorrhynchans were found on graminoid hosts (Poaceae and Cyperaceae); there was little observed plant-specificity beyond this. There were no significant correlations between presence of subterranean sternorrhynchans and percent cover of different plant types, soil moisture content, slope, aspect, or visible entrances to ant nests.
Surveys were conducted to determine the parasitoid communities associated with the cabbage seedpod weevil, Ceutorhynchus obstrictus (Marsham), an important invasive pest of canola in Ontario and Quebec, Canada. More than 18 species of Chalcidoidea (Hymenoptera) were associated with this pest through mass rearings from canola siliques. In southwestern Ontario, the most abundant species were a species of Chlorocytus Graham (23.6%–48.6%), Lyrcus perdubius (Girault) (0%–53%), L. maculatus (Gahan) (2.8%–14.7%), and species of Pteromalus Swederus (0.6%–23.1%) (Pteromalidae). In contrast, the most abundant species in Quebec were Trichomalus lucidus (Walker) (Pteromalidae) (33.3%–56.4%), unidentified Eulophidae (2.1%–39.1%), Mesopolobus gemellus Baur and Muller (Pteromalidae) (1.3!.4%), and Necremnus tidius (Walker) (Eulophidae) (11.5%–19.3%). In the Ottawa, Ontario, area, parasitoids were first recovered in 2008, and Trichomalus perfectus (Walker) (Pteromalidae), M. gemellus, and species of Pteromalus were most prevalent. Mesopolobus gemellus and T. perfectus are reported in North America for the first time. Although existing communities appear to provide substantial parasitism (e.g., 6.3%–26.3% in 2006), species composition varies among years and differs from that in other regions in North America. Thus, parasitism levels and parasitoid communities of the cabbage seedpod weevil should be monitored to assess whether these will increase or there is a need to introduce more host-specific species from Europe that could provide greater mortality.