Chemical defense of an earwig (Doru taeniatum)

The earwig Doru taeniatum (Dermaptera, Forficulidae) has a pair of defensiv e glands, opening on the 4th abdominal tergite, from which it discharges a spray when disturbed. It aims the discharges by revolving the abdomen, a ma neuver that enables it simultaneously to use its pincers in defense. The se cretion contains two quinones (methyl-1,4-benzoquinone and 2,3-dimethyl-1,4 -benzoquinone) present in the glands as a crystalline mass, together with p entadecane and a (presumably) aqueous phase. The gland openings are minute, with the result that virtually no quinone crystals are expelled with the s pray. Only the two liquid phases are discharged, together with the ca. 1% q uinone they carry in solution. Such a solute-economizing discharge mechanis m appears to be without parallel among insect defensive glands.