Sampling Efficacy and Survival Rates of Labarrus pseudolividus (Coleoptera: Scarabaeidae) and Onthophagus taurus (Coleoptera: Scarabaeidae) Using Flotation and Sieve-Separation Methodology.

Understanding collection methodologies and their limitations are essential when targeting specific arthropods for use in habitat restoration, conservation, laboratory colony formation, or when holistically representing local populations using ecological surveys. For dung beetles, the most popular collection methodology is baited traps, followed by light traps and unbaited flight-intercept traps during diversity surveys. A less common collection method, flotation, is assumed to be laborious and messy, and so only a handful of papers exist on its refinement and strengths. Our purpose was threefold: First, we tested the recovery and survival rates of Labarrus (=Aphodius) pseudolividus (Balthasar) and Onthophagus taurus (Schreber) when floating beetle-seeded dung pats to determine potential collection and safety issues. We collected 72.4 and 78% of the seeded L. pseudolividus and O. taurus, respectively, with >95% survival rating. Second, we developed a flotation-sieving technique that enables users to rapidly collect and passively sort dung beetles with less time and effort. Specifically, we often collected 50-100 g of wild dung beetles within a couple of hours of gathering dung and sorted them in a couple more by allowing dung beetles to sort themselves by size within a series of sieves; Third, we reviewed flotation-based advantages and disadvantages in comparison to other methodologies.

Carbon Neutral: The Failure of Dung Beetles (Coleoptera: Scarabaeidae) to Affect Dung-Generated Greenhouse Gases in the Pasture.

Research suggests dung beetles can churn, aerate, and desiccate dung in ways that influence the dung and soil microbes producing greenhouse gases (GHGs). We examined the impacts of the tunneling beetle, Onthophagus taurus (Schreber), and the dwelling beetle, Labarrus pseudolividus (Balthasar), on the carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) emitted from pasture-laid bovine dung as well as their sum-total (CO2 + CH4 + N2O) effect on global warming, or their carbon dioxide equivalent (CO2e). Despite dung beetles potential effects on CH4 and N2O, the existing literature shows no ultimate CO2e reductions. We hypothesized that more dung beetles would degrade pats faster and reduce CO2e, and so we increased the average dung beetle biomass per dung volume 6.22× above previously published records, and visually documented any dung damage. However, the time effects were 2-5× greater for any GHG and CO2e (E = 0.27-0.77) than dung beetle effects alone (E = 0.09-0.24). This suggests that dung beetle communities cannot adequately reduce GHGs unless they can accelerate dung decomposition faster than time alone.

Effects of Fatty Acid and Geraniol Repellent-Oil Mixtures Applied to Cattle on Blood Feeding and Reproductive Parameters in Field Populations of Haematobia irritans (Diptera: Muscidae).

California pastured cattle were treated with 250 ml of a 15% mixture of fatty acids (C8-C9-C10) or 125 ml of 2% geraniol in a mineral oil carrier to assess impacts on horn flies, Haematobia irritans (L.) (Diptera: Muscidae) over two summers. Horn flies were netted from cattle every 3-4 d for 2 wk before treatment, 2 wk during treatment (four treatments, with flies collected before each treatment), and 2 wk after treatments ceased. Blood meal weights were estimated by hemoglobin assay of excised abdomens. Other females were dissected to determine the number of active ovarioles and the stage of primary follicle development. Depending on year and herd, pretreatment males contained an average of 0.6-1.0 mg of blood, while females contained 1.7-2.7 mg. Pretreatment egg development (least developed oocytes were stage 1 and fully developed eggs were stage 5) averaged 3.7-4.3, and number of active ovarioles averaged 18.1 to 19.6/female. During treatment periods, significant reductions in blood weight were noted for females, but usually not for males, and females also often exhibited reduced mean oocyte stage and number of active ovarioles. Peaks in proportions of young nulliparous females (oocyte stages 1 or 2) were seen during some repellent application periods. This suggested older females had been killed or driven off from the local population by the treatments, and flies on cattle included more young flies that likely were recent arrivals. The repellent-oil mixture thus impacted blood feeding, reproductive fitness, and probably age structure in the field.

Survival of the House Fly (Diptera: Muscidae) on Truvia and Other Sweeteners.

The house fly, Musca domestica L. (Diptera: Muscidae), is a disease vector of mechanically transmitted pathogens including bacteria, viruses, and protozoans. Opportunities for pathogen transmission can increase as fly longevity increases. Dietary preferences play an important role in insect longevity; therefore, we investigated house fly preferences, sucrose availability, and caloric constraints on house fly longevity. Experimental goals were: 1) to test the effects of calorie restriction on survival of house flies by manipulating concentrations of erythritol (low caloric content) and sucrose (high caloric content), and comparing commercial sweeteners of differing calorie content, 2) to identify house fly preferences for either erythritol or sucrose, and 3) to evaluate the insecticidal activity or toxicity of erythritol on house flies. Our data show that house flies may prefer high calorie options when given a choice and that house fly longevity likely increases as calorie content increases. Additionally, no significant differences in longevity were observed between the water only control (zero calories) and erythritol treatments. This suggests that decreased survival rates and death could be the result of starvation rather than insecticidal activity. This research furthers our understanding of house fly survival and sugar-feeding behavior.

Seasonality and Diapause of Musca autumnalis (Diptera: Muscidae) at its Southern Limits in North America, With Observations on Haematobia irritans (Diptera: Muscidae).

The face fly (Musca autumnalis De Geer) and horn fly (Haematobia irritans ([L.])) were studied at the southern edge of the face fly's North American range, examining southern California geographic distribution, seasonal activity on cattle and in dung, and diapause. Face flies were common only at Pomona (34°03'N, 117°48'W). Other irrigated pastures, even those only slightly inland from Pomona, were probably too warm for face flies, due to a steep west (cooler) to east (warmer) temperature gradient. Horn flies were abundant at all sites. Adult densities on cattle, adults emerging from dung pats, and prevalence of fly-positive pats were assessed for both fly species throughout a year at Pomona. Summer adult horn fly densities of 500-2,000 flies per cow, or face fly densities of 3-10 flies per face, were common. Summer prevalence of face fly-positive pats and horn fly-positive pats was about 20-40% and 30-70%, respectively. Face fly adults diapaused from late October until late March and early April. Horn flies probably diapaused as pupae from late October or early November to early-mid March, although some emerged in winter. Experimental cohorts of October-emerging adult face flies were held in a representative overwintering site. They exhibited hypertrophied fat body and undeveloped oocytes, which are characteristics of diapause, and survived until the following spring. The dominant diapause cues in face and horn flies are probably photoperiod and temperature. Despite warm winter temperatures that would permit activity of both species, and despite relatively long winter day lengths, face flies and most horn flies still diapaused at this latitude.

Musca autumnalis (Diptera: Muscidae) and the host-specific nematode Paraiotonchium autumnale (Tylenchida: Iotonchiidae) in southern California.

Musca autumnalis DeGeer were collected in the summer and fall of 2011 and 2012 from a beef cattle herd in southern California Visual counts of Musca spp. on cattle faces were documented, and sweep net samples of face flies and other Diptera were also collected from cattle faces. Face flies dominated in the net collections, and 5-30 flies per face were common between early July and October 2011. Adult female M. autumnalis were dissected and examined for the presence of the host-specific nematode Paraiotonchium autumnale (Nickle). Overall, 67 of 887 (7.6%) adult face fly females were parasitized. M. autumnalis' ability to survive in such a southerly latitude (34 degree N) could reflect the rather temperate weather (coastal effects) and frequently irrigated pastures at the experimental site in southern California Preliminary observations suggest that face flies disappear from cattle during winter, despite generally favorable temperatures for fly activity. This is a possible indication of diapause and should be examined further.