A standardised method of marking male mosquitoes with fluorescent dust

Background: Prior to a major release campaign of sterile insects, including the sterile insect technique, male mosquitoes must be marked and released (small scale) to determine key parameters including wild population abundance, dispersal and survival.Marking insects has been routinely carried out for over 100 years, however, there is no gold standard regarding the marking of specific disease-transmitting mosquitoes including Anopheles arabiensis, Aedes aegypti and Aedes albopictus . The research presented offersa novel dusting technique and optimal dust colour and quantities, suitable for small-scale releases, such as mark-release-recapture studies. Methods: We sought to establish a suitable dust colour and quantity for batches of 100 male An. arabiensis , that was visible both by eye and under UV light, long lasting and did not negatively impact longevity. A set of lower dust weights were selected to conduct longevity experiments with both Ae. aegypti and Ae. albopictus to underpin the optimal dust weight. A further study assessed the potential of marked male An. arabiensis to transfer their mark to undusted males and females. Results: The longevity of male An. arabiensis marked with various dust colours was not significantly reduced when compared to unmarked controls. Furthermore, the chosen dust quantity (5 mg) did not negatively impact longevity ( P = 0.717) and provided a long-lasting mark. Dust transfer was found to occur from marked An. arabiensis males to unmarked males and females when left in close proximity. However, this was only noticeable when examining individuals under a stereomicroscope and thus deemed negligible. Overall, male Ae. aegypti and Ae. albopictus displayed a greater sensitivity to dusting. Only the lowest dust weight (0.5 mg) did not significantly reduce longevity ( P = 0.888) in Ae. aegypti, whilst the lowest two dust weights (0.5 and 0.75 mg) had no significant impact on longevity ( P = 0.951 and 0.166) respectively in Ae. albopictus . Conclusion: We have devised a fast, inexpensive and simple marking method and provided recommended dust quantities for several major species of disease-causing mosquitoes. The novel technique provides an evenly distributed, long-lasting mark which is non-detrimental. Our results will be useful for future MRR studies, prior to a major release campaign.

Can Attractive Sticky Traps Be Used to Protect Horses From the Bites of Stomoxys calcitrans (L.) (Diptera: Muscidae)

The stable fly, Stomoxys calcitrans (L.), is a bloodsucking ectoparasite that causes irritation and distress to livestock, wildlife, and humans. Both sexes are vicious blood-feeders that feed on a variety of animals. Optically attractive sticky traps have been used to capture stable flies, and some companies claim that sticky traps can protect animals from the bites of stable flies. To further investigate the protective ability of sticky traps, Home and Garden Mosquito (HGM) traps were selected for evaluations at the University of Florida Horse Teaching Unit (HTU). Broodmares coated with fluorescent dust were either tethered to a post in the center of a paddock or released untethered into a paddock. HGM sticky traps were placed at the four compass points and four selected distances from the paddock center to capture stable flies before (unmarked) or after (marked) they visited the horses. More than 40% of flies captured on traps placed closest to the horses were marked. This indicates that the traps did not prevent the flies from visiting the horses. A percentage of marked and unmarked stable flies showed signs of blood in their guts indicating recent feeding. For unknown reasons, the number of stable flies marked with Signal Green dust exceeded the numbers marked with other colors. Although the HGM traps caught ample numbers of stable flies, the traps did not prevent stable flies from feeding on the horses. More work is needed to determine optimal trap placement and densities required to maximize stable fly management with traps.

Estimates of population density and dispersal in the blowfly Lucilia sericata (Diptera: Calliphoridae)

To investigate the population density and dispersal of the sheep blowfly Lucilia sericata (Meigen) mark-release-recapture trials were carried out in lowland pastures in south west England. In three trials, 2142, 1351 and 451 fluorescent dust marked flies were released of which 4%, 14% and 10% were recaptured using a grid of sticky, odour-baited targets, placed between 8 m and 1000 m from the release point. There was no significant effect of wind direction on dispersal pattern and no apparent directional movement of the flies from the release point. Using the method described by Hawkes (1972) the mean distance travelled by all the flies on the first day of each of the three trials was calculated to be 108 m, 128 m and 137 m respectively. Using the method described by Fletcher (1974) the mean distances travelled were calculated to be 135 m (±42), 118 m (±27) and 183 m (± 61) on the first day of each of the three trials, respectively. The median distances travelled by the flies on the first day of each of the three trials were calculated to be 109 m, 130 m and 150 m, respectively. A Lincoln Index was used to estimate the population density of wild female L. sericata. The number of female flies was estimated to be zero in June, approximately one per hectare in July and six per hectare in August in 1994.