Linamarin and histamine in the defense of adultZygaena filipendulae.

We determined the protective values of histamine and linamarin to an aposematic moth,Zygaena filipendulae. Using ion-exchange resin techniques, we found that the mean histamine concentrations in the wings were 0.061 ± 0.047 μg/mg and 0.013 ± 0.0051 in the moths' bodies (totals: 0.586 μg and 2.921 μg, respectively, all wet weights). Average HCN evolution (mainly from the bitter cyanogen linamarin) from the wings was 0.049 ± 0.41 μg/mg (0.426 μg/ml of linamarin could produce this amount of HCN) and 0.029 ± 0.0026 μg/mg HCN (0.281 μg/mg linamarin) evolved from the bodies (total linamarin 4.09 μg and 61.258 μg, respectively, all wet weights). Therefore, higher concentrations of toxicants were found in the part of the body most liable to initial attack. We found, in offering various toxic solutions to 10 common quails, that 0.1% linamarin (mean linamarin consumed equal to about 70% of the average total wing content) but 1.0% histamine (mean histamine consumed equal to that found in about 8.9 average wing sets) solutions significantly lowered drinking rates. However, combination solutions were still effectively aversive at 0.001% histamine plus 0.028% linamarin. This synergism would allow a moth under local abiotic or dietary stress to elaborate substantially less of one or both compounds than that normally synthesized. The implications to kin selection are discussed.