Department of Entomology

Amino sugars, being predominantly of microbial origin, can help elucidate the role of microbes in carbon and nitrogen cycling in soils. However, little is known about the microbial degradation and synthesis of soil amino sugars as affected by plant-derived organic materials. We conducted a 30-week microcosm study using three soils amended with soybean leaf or maize stalk to investigate changes in the amounts and patterns of amino sugars over time. The total soil amino sugar content initially increased during the incubation, but later decreased. Amino sugar content of soil amended with maize stalk peaked at an earlier time than it did for soybean leaf, suggesting nutrient quantity and substrate composition influence microbial transformation. Temporal dynamics of the proportion of total soil amino sugar to organic matter after plant material addition conformed to parabolic models (r > 0.8; p < 0.01), which tended to converge over time. The models predicted that the proportions would ultimately approach the initial values as determined before amendment. These findings suggest that soil organic matter has the ability to maintain a baseline steady-state level of amino sugars, and support the interpretation of soil amino sugar reservoir as two components: the Stable Pool (SP) and the Transition Pool (TP).

A statewide survey of Wisconsin’s Nemonychidae and Anthribidae (Coleoptera: Curculionoidea) was conducted over one full (2012) and two partial (2011, 2013) field seasons. Specimens were collected using a variety of techniques. Two species of the nemonychid genus Cimberis and 22 species of Anthribidae in 13 genera are now confi rmed. Generic and species-level keys for Wisconsin species are provided along with generic and species diagnoses. Species treatments also include a synonymy, a description, and information on natural history, phenology, distribution and collecting methods. Dorsal and lateral habitus images are also provided for most of the species.

The venoms ofPolistes exclamans andP. fuscatus elicit alarm behavior and attract attacking wasps. The response is not species specific, for both hetero- and conspecific venoms elicit similar responses in both species. A test in a wind tunnel provided no support for the hypothesis that alarmed wasps release an alarm pheromone on the nest.

In the laboratory overwintered females of Polistes fuscatus preferentially associated with former nestmates during the founding of a colony. They did not associate with non-nestmates or only with nestmates with whom they had overwintered, but affiliated with all former nestmates, regardless of where the former nestmates overwintered.

Although tapping the nest in simulated vertebrate attack caused all but 1-day-old workers of Polybia occidentalis to rush from inside and cover the envelope, defense itself—attack of a target—was shown to be carried out only by workers older than about 10 days. While foraging was also performed by older workers, the frequency-age distribution of defensive behavior was skewed to a significantly younger age than was that of foraging. The plot of mean individual probability of defending as a function of age was logistic, leveling off at 0.11 by the age of about 13 days. The distribution of the probability of defending among workers ≥ 13 days of age was random, indicating that there is no specialized defender class among older workers. Workers that defended were recruited from among both nest workers and foragers. Although foragers were more likely to defend than were nonforagers, nonforagers contributed more individuals to the pool of defenders because they were more numerous.

Abstract. Topical applications of the Juvenile Hormone (JH) analogue methoprene to 1-day-old adult workers of the highly eusocial wasp Polybia occidentalis (Olivier) (Hymenoptera: Vespidae) accelerate the rate of age polyethism. Longevity of laboratory-reared wasps is negatively correlated with dose of topically applied methoprene. Doses of 25 μg methoprene or greater are lethal. Untreated wasps show marked age polyethism in the field. Age of first performance of acts in seven behavioural categories (in-nest, transition to outside, non-task on nest envelope, nest maintenance, foraged material handling, defence, and foraging) is negatively correlated with methoprene dose. Topical applications of methoprene accelerate age polyethism of highly eusocial bee and wasp workers, but do not have this effect on primitively eusocial bees and wasps, suggesting that JH control of age polyethism evolved independently in advanced species of Apidae and Vespidae.

Behavior in eusocial insects likely reflects a long history of selection imposed by parasites and pathogens because the conditions of group living often favor the transmission of infection among nestmates. Yet, relatively few studies have quantified the effects of parasites on both the level of individual colony members and of colony success, making it difficult to assess the relative importance of different parasites to the behavioral ecology of their social insect hosts. Colonies of Polybia occidentalis, a Neotropical social wasp, are commonly infected by gregarines (Phylum Apicomplexa; Order Eugregarinida) during the wet season in Guanacaste, Costa Rica. To determine the effect of gregarine infection on individual workers in P. occidentalis, we measured foraging rates of marked wasps from colonies comprising both infected and uninfected individuals. To assess the effect of gregarines on colony success, we measured productivity and adult mortality rates in colonies with different levels of infection prevalence (proportion of adults infected). Foraging rates in marked individuals were negatively correlated with the intensity of gregarine infection. Infected colonies with high gregarine prevalence constructed nests with fewer brood cells per capita, produced less brood biomass per capita, and, surprisingly, experienced lower adult mortality rates than did uninfected or lightly infected colonies. These data strongly suggest that gregarine infection lowers foraging rates, thus reducing risk to foragers and, consequently, reducing adult mortality rates, while at the same time lowering per-capita input of materials and colony productivity. In infected colonies, queen populations were infected with a lower prevalence than were workers. Intra-colony infection prevalence decreased dramatically in the P. occidentalis population during the wet season.