Canopy Trap Research Articles

Tabanid (Diptera) populations associated with an equine infectious anemia outbreak in an inapparently infected herd of horses.

Seven horses positive for antibodies to equine infectious anemia virus in the agar gel immunodiffusion test were maintained together with 8 test-negative horses in an isolated pasture in south Louisiana for 1 year. Although the test-positive horses were inapparently infected (exhibiting no clinical signs of equine infectious anemia), 6 of the 8 test-negative horses became test-positive during 1 vector season. Canopy trap surveillance revealed Hybomitra lasiophthalma as the only tabanid species present during 2 equine infectious anemia virus transmissions in March. A high population of Tabanus lineola was present during the remaining 4 virus transmissions in July, September, and October.

ASPECTS OF THE BIOLOGY OF FEMALE CHRYSOPS UNIVITTATUS (DIPTERA: TABANIDAE) IN SOUTHWESTERN QUEBEC

AbstractChrysops univittatus Macquart females were more abundant in late July and early August in southwestern Quebec. Dry-ice baited canopy trap collections consisted of 55% (n = 177) of the nulliparous and 77% (n = 91) of the parous females. Incidence of nectar feeding, as determined by cold anthrone test, was 73% (n = 244) and 96% (n = 268) of the females contained sperm; no difference was found between parous and nulliparous females. This species is anautogenous, and only one gonotrophic cycle was recorded following ovary dissection. Number of ovarioles was correlated with body size (as determined by wing length) by linear regression analysis.

Physiological age of Tabanidae (Diptera) in eastern New York State, U.S.A.

The physiological age and developmental stages of terminal follicles were determined for females of 30 tabanid species (12 Chrysops , 8 Hybomitra , and 10 Tabanus ). During July 1974, 21 species were obtained in canopy trap and sweep collections; H. lasiophthalma was the most abundant species in the. canopy trap during June and July. Of 1789 females collected, 1523 were dissected to determine physiological age and stage of follicle development. Nullipars with follicles in stage II were most frequently collected; stage II ovarian diapause was found in most species. Populations of the following species were anautogenous: C. ater, C. callidus, C. indus, C. macquarti, C. vittatus, H. epistates, H. illota, H. lasiophthalma, H. nuda, H. sodalis, T. lineola, T. quinquevittatus, T. similis, T. sparus milleri , and T. sulcifrons . Fifty-five percent of parous specimens having sacstage follicular tubes had yolk deposited in terminal follicles, while 99% of pars with distinct “yellow bodies” had follicles in this condition.

Trypanosomes in Horse Flies and Deer Flies in Central New York State

Tabanids were collected during 2 consecutive summers from 3 counties in New York using a canopy trap and insect net. Twenty-seven per cent of all fly specimens (N equals 641) representing 69% of the species collected (N equals 36) were infected with flagellates. Tabanid intestines harbored amastigote, choanomastigote, and epimastigote forms. Epimastigotes were frequently found, and trypomastigotes and choanomastigotes rarely found in cultures of tabanid intestinal flagellates. Epimastigote and trypomastigote forms closely resembled Trypanosoma theileri-like trypanosomes reported from ruminants.

A Device for Self-marking of Tabanidae

Few methods have been described for marking tabanids. Bennett and Smith (1968) marked them with 32 p in water which the flies imbibed. Thornhill et al. (1971), and Thornhill and Hays (1972) marked flies with model airplane dope. Face flies, Musca autumnalis De Geer, were marked successfully with fluorescent powder for field studies (Turner and Gerhardt 1965). In studying tabanid flight in Louisiana we wanted to mark large numbers of flies with a minimum of interference. We allowed the flies to mark themselves with Day-Glo fluorescent pigments 3 as they passed through a selfmarking device mounted on a canopy trap (Catts 1970), as modified by Adkins et al. (1972).

Relationship between host attack rates and CO 2 -baited insect flight trap catches of certain Symphoromyia species.

Correlation coefficients of 0.612 and 0.884, respectively, for the numbers of females of Symphoromyia sackeni and members of the S. pachyceras complex attacking deer versus those caught in traps emitting ca 2.4 liters CO2/min. established that trap catches excellently reflected the day-to-day activity of the host-seeking portion of the fly populations as measured by their proportional activity at unrestrained hosts. The adjusted x¯ numbers of females attacking hosts per day were nearly identical to the x¯ numbers of females caught in traps per day. As traps also proportionately caught females in the same gametogenic states as those collected from deer, we conclude that the traps functioned as substitutes for deer for these host specific flies, particularly with respect to the numbers of the S. pachyceras complex caught each day versus the numbers attacking deer. This is the first report of a trap which quantitatively functions as a substitute for the natural host with respect to the daily attack rate of a hematophagous arthropod. There were highly significant differences among sites with regard to trap catches of both S. sackeni and members of the S. pachyceras complex. Catches of the latter were proportional to the percentage canopy cover surrounding trap sites, whereas wind direction had the greatest effect on the numbers of S. sackeni caught at each site. The relationships between canopy Cover, trap locations and catches, and wind directions showed that both S. sackeni and members of the S. pachyceras complex responded to the traps by orienting in an upwind direction and that the flies were being attracted from distances of up to 50 to 60 m. Comparison of the ratios of S. sackeni to the S. pachyceras complex at deer to their ratios in traps showed that the former species remained near its peak population density whereas the population of the latter declined rapidly during the study. Other data indicated that the traps were less attractive for S. sackeni than for members of the S. pachyceras complex. Although S. sackeni was considerably more abundant during the study than the members of the S. pachyceras complex, and the species which we nearly always caught in fewer numbers than expected in the traps, it was the species whose segments of the populations were strikingly trapped out from about a 5-ha area by a concentration of 5 traps. This seeming paradox is c1arified by postulated differences in the behavior of S. sackeni and members of the S. pachyceras complex. In addition to Symphoromyia species, CO2-baited traps caught large numbers of many obligate and facultative mammalophilic bloodfceding species. None or only few of any specieswere caught in unbaited traps.