Analysis of anal droplets of the western flower thrips Frankliniella occidentalis

Larvae of the western flower thrips Frankliniella occidentalis are known to produce an anal droplet containing decyl acetate (10Ac) and dodecyl acetate (12Ac), which act as an alarm pheromone. Analysis by GC showed that the combined mass of 10Ac and 12Ac per droplet increased with age of second instars from 2 ng to 18 ng, while the mass ratio of 10Ac: 12Ac increased from 0.4: 1 to 1.1: 1 ( molar ratio 0.4: 1 to 1.2: 1). Droplet volume increased from 0.4 nl to 2.1 nl with age, but only about 1% of this was accounted for by 10Ac and 12Ac. The remainder contained water. Analysis by GC-MS using SPME revealed no other volatile components. Whole bodies contained about two to four times as much 10Ac and 12Ac as a droplet, but in a similar ratio.