Endocoprid activity of Aphodius fossor (Coleoptera: Scarabaeidae) related to bovine dung decomposition in a mixed grass prairie.

Aphodius fossor (L.) (Coleoptera: Scarabaeidae), a common endocoprid dung beetle in southeastern Wyoming, may have a survival strategy to maintain dung pad integrity and moisture crucial to larval survival in an arid climate (annual precipitation <30 cm). Typically, A. fossor seems to contribute little to dung pad decomposition, because inhabited dung pads seem to be intact and weigh approximately the same as uninhabited pads, even after 1 yr on pasture. To assess the role of A. fossor in dung pad decomposition and nutrient recycling, artificially formed bovine dung pads were inoculated with five pairs of adult A. fossor. After 40 d, A. fossor activity had no measurable effect on external surface area or moisture retention within the dung pad cores. Pads inhabited by A. fossor weighed significantly more than did control pads on most weigh dates of the experiment, possibly because of incorporation of soil particles at the dung/soil interface. Externally, A. fossor-inhabited dung pads seemed intact; however extensive tunneling was evident throughout the core of the pad leaving an intact, protective crust. A. fossor activity increased microbial biomass carbon in the soil beneath the dung pad. Levels of total nitrogen (N) and carbon (C) decreased in the pads but increased in soil beneath the pads. Dung in the core and in the crust of pads with A. fossor had significantly less total N than pads with no beetles and total C was significantly lower in the crust.

Suppression of bloodfeeding by Ochlerotatus dorsalis and Ochlerotatus melanimon on cattle treated with python ear tags.

Adult mosquitoes were collected by drop traps to compare bloodfeeding rates between cattle treated with 2 Python ear tags (10% zeta-cypermethrin and 20% piperonyl butoxide) per animal and animals that were untreated. Mosquitoes were collected both 2 and 4 wk after application of the ear tags. Bloodfeeding by Ochlerotatus dorsalis was reduced by 79 and 77%, respectively, and bloodfeeding by Ochlerotatus melanimon was reduced by 84 and 81%, respectively, at 2 and 4 wk. Based on chi-square analysis, differences in bloodfeeding rates due to treatment were significant. The effect of the treatment appeared to be repellency, because no mosquito mortality was observed at the time of collection and no mortality was observed among bloodfed mosquitoes that were collected and held for 24 h.

Simulated predictions of insect phenological events made by using mean and median functional lower developmental thresholds.

A computer-simulated study was conducted to determine whether mean or median functional lower developmental thresholds and required degree-days were superior for predicting the dates on which insect phenological events occurred. In addition, these simulations allowed us to determine if the type of year (weatherwise) influenced those predictions. Results indicated that when median functional lower developmental thresholds and required degree-days were used their predictions were closer to the dates on which the phenological events occurred than were predictions that were made using mean thresholds and required degree-days. Also, the predictions of phenological events made when using median functional lower developmental thresholds and required degree-days were not strongly influenced by the type of year. However, the influence of type of year was quite strong when predictions were made when using mean thresholds and required degree-days. The variability in predictions that were made when using median functional lower developmental thresholds and required degree-days was greater than the variability in predictions that were made when using mean thresholds and required degree days. However, the increased variability was caused by many predictions being closer to, rather than farther from, the actual dates on which the phenological events occurred. Based on these findings, we suggest that median functional lower developmental thresholds, along with median required degree-days, be considered for use when predicting insect phenological events in the field.

Seasonal movement and spatial distribution of the sheep ked (Diptera: Hippoboscidae) on Wyoming lambs.

When populations of adult sheep ked, Melophagus ovinus (L.), infesting unshorn lambs were monitored at the University of Wyoming Paradise Farm during 1986, we determined the body regions on which keds would be found at various times of the year and their seasonal population trends for optimal sampling. Results suggested that ked populations were consistently greater on the ribs than on any other area of the lamb. No significant differences were detected for ked populations between sides of a lamb. Distinct and similar ked population trends over time occurred only in the rib, thigh, shoulder, hind leg, belly, and hind flank areas of the lambs, suggesting that a significant seasonal migration did not occur. Analyses for seasonal population fluctuations indicated that ked populations increased in the winter and spring, decreased in summer and then increased again in the fall. Thus, sampling for keds in the rib area at shearing, which begins in March in Wyoming and runs through mid-April, would be an opportune time to detect keds. At other times of the year, the rib area should be inspected for presence of sheep ked.