In a field study attempting to test potential repellency of defensive chemicals on Lygus lineolaris (Heteroptera: Miridae), a small Chloropid fly, Olcella trigramma was caught in large numbers in ester-baited traps. Further field trapping experiments indicated that hexyl butyrate (HB; 4.2-8.4 mg/d) and (E)-2-hexenyl butyrate (E2HB; 1.4-2.8 mg/d), the major defensive chemicals found from the Lygus bugs, were strongly attractive to this fly (mostly females), while blank control traps were unattractive. E2HB (2.8mg/d) seemed to be more attractive than HB (8,4 mg/d) did. When these two esters were combined in the same trap 3 times more flies were caught. Factorial ANOVA analysis indicated a significant synergistic effect between these two defensive chemicals. Tests of ester ratios (0%; 10%; 25%; 50%; 75%; 90%; 100% HB) not only supported the synergistic effect, but also showed optimal ratios range from 90% to 50% HB, which is similar to the natural ratio (F=45%HB; M=95% HB) of these two defensive chemicals found in the metathoracic scent glands (MSG) of L. lineolaris. In an electroantennogram (EAG) study, O. trigramma female antennae strongly responded to E2HB, followed by HB, while EAG responses to two shorter chain esters, butyl butyrate and pentyl butyrate, were not significantly different from blank control. Our results suggest that O. trigramma are able to recognize Lygus bugs (most likely the dead bugs) by detecting their major defensive chemicals released or leaked from MSG glands, and by responding optimally to their specific natural ratios.
Species 1: Diptera Chloropidae Olcella trigramma (grass flies)
Species 2: Heteroptera Miridae Lygus lineolaris (Tarnished Plant Bug)
Keywords: hexyl butyrate, E-2-hexenyl butyrate
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