Aggregation behavior and a putative sex pheromone in the sugar beet root maggot fly, Tetanops myopaeformis

Field observations showed that male-biased aggregations of sugar beet root maggot flies, Tetanops myopaeformis (Röder), occur on utility poles near sugar beet fields; this contrasts with the approximately equal sex ratio for flies observed within beet fields. Peak observation of mating pairs on utility poles coincided with peak diurnal abundance of flies. Volatiles released by individual male and female T. myopaeformis flies were sampled from 08:00h to 24:00h in the laboratory using solid phase microextraction (SPME) and analyzed by gas chromatography / mass spectrometry (GC-MS). Ten compounds were uniquely detected from males. Three of these compounds (2-undecanol, 2-decanol, and sec-nonyl acetate) were only detected between 12:00h and 16:00h. Another seven compounds (i.e., 6,10-dimethyl-5,9­ undecadiene-2-one, dodecanal, tetradecane, pentadecane, and three unknowns) were also uniquely detected from males; however, these did not exhibit temporal trends in release during the sampling period. Both males and females produced 2-nonanol, but males produced substantially higher (ca. 80-fold) concentrations of this compound than females, with the greatest production again occurring during sample periods beginning at 12:00h. The temporal synchrony among male aggregation behavior, peak mating rates, and release of certain volatile compounds by males suggests that T. myopaeformis flies exhibit lekking behavior and produce a pheromone. Field assays using synthetic blends of the putative pheromone (comprising nine volatiles sampled from males) showed evidence of female attraction, especially at the highest dose tested.