Olfactory and behavioural responses of tabanid horseflies to octenol, phenols and aged horse urine

Abstract

Electrophysiological and behavioural responses of females of two tabanid species, Tabanus bromius L. and Atylotus quadrifarius (Loew) (Diptera: Tabanidae), to ammonia, octenol (1-octen-3-ol), phenols and aged horse urine were compared. Electroantennogram (EAG) responses in both species to octenol, 4-methylphenol (4MP), 3-propylphenol (3PP) and a phenol mixture (4MP and 3PP at a ratio of 16 : 1) increased in a dose-dependent fashion. The most effective stimulus was 4MP and synergism between the two phenols may exist. Aged horse urine also elicited strong EAG responses in both species. Using gas chromatography-mass spectrometry (GC-MS) analysis, we identified 29 compounds in horse urine, which included, in particular, ketones, fatty alcohols and phenols, among which 4MP was the most abundant component (~ 80%). Trapping experiments were carried out using Nzi traps baited with various odours. Octenol and the phenol mixture in combination with ammonia increased catches of tabanids by 1.8-2.8 times relative to ammonia alone. Aged horse urine increased catches of T. bromius and A. quadrifarius by 2.2 and 4.1 times, respectively. The high attractiveness of aged horse urine, especially for A. quadrifarius, is not likely to derive from 4MP alone, but from the mixture of various active compounds used in host location.

Biting behaviour of Tabanidae on cattle in mountainous summer pastures, Pyrenees, France, and effects of weather variables

“…Tabanids are haematophagous Diptera that are mostly diurnal, and their daily activity patterns have been observed to be related to meteorological conditions, such as wind velocity, temperature, relative humidity, evaporation, atmospheric pressure and sky radiation or cloud cover (Burnett & Hays, 1974; Dale & Axtell, 1975; Alverson & Noblet, 1977; Van Hennekeler et al , 2011). In a study in Southeastern France, daily catches of T. bromius and Atylotus quadrifarius appeared to be positively correlated with temperature and/or negatively correlated with wind speed (Baldacchino et al , 2013 a , c ), as in our observations in the Pyrenees. More generally, temperature and wind speed have been shown through GLMM analysis to drive variation in the daytime aerial density and displacement speed of insects (Bell et al , 2013).…”

Behavior and Electrophysiological Response of Gravid and Non-Gravid Lucilia cuprina (Diptera: Calliphoridae) to Carrion-Associated Compounds

“…For example, in Musca domestica, DMTS evokes an EAG response but not a behavioral response (Zito et al 2014). Both Tabanus bromius and Atylotus quadrifarius display EAG responses that differ in intensity between 1-octen-3-ol and phenols, but the responses in trap experiments are similar for the two compounds (Baldacchino et al 2014). This sort of inconsistency between EAG and behavioral outcomes to a single compound has also been demonstrated for flower-visiting insects and floral scents (Jhumur et al 2007, Xu et al 2015, Bohman et al 2016.…”

Attractiveness of thermally different, uniformly black targets to horseflies:Tabanus tergestinusprefers sunlit warm shiny dark targets

“…Although we could not determine the sex of tabanids ( T. tergestinus ) in our field experiments, most of them were females in all probability, because such targets attract only females. On the one hand, it is well known that the shiny black sphere of the Manitoba trap attracts exclusively female tabanids; thus, this and similar traps capture only females [4,8,9,10,19,21,22,23,27,38,68]. On the other hand, in our earlier field experiments, the shiny black sticky or dry (non-sticky) vertical traps caught only female tabanids [12,15,16,33,35,40,48,49].…”