Journal of Chemical Ecology, Vol. 25, No. 3, 1999 DEFENSE SECRETION OF Prorhinotermes simplex: TOXICITY TO INSECTICIDE SUSCEPTIBLE AND RESISTANT HOUSE FLY1 JELENA KULDOVA,* IVAN HRDY, and ALES SVATOS Institute of Organic Chemistry and Biochemistry Academy of Sciences of Czech Republic Flemingovo n. 2, 166 10 Praha 6, Czech Republic (Received April 30, 1998; accepted November 12, 1998) Abstract—(E)-1-Nitropentadec-1-ene (NPE), the main component of the de- fense secretion of Prorhinotermes simplex soldiers, is toxic to both insecticide-susceptible (S) as well as to insecticide-resistant (R) strains of the house fly, Musca domestica. The LD50 is 11.7 ug/female fly for the S strain and 9.7 ug for the R strain. The same efficacy of NPE on R and S strains indicates a different mechanism of action compared to conventional chlorinated, organophosphorus, and pyrethroid insecticides. Termite nestmates are protected against NPE by a specific detoxification mechanism. 1-Nitropentadecane, the detoxification product of NPE is nearly nontoxic to house flies, and doses up to 160 ug/fly caused only very low mortality. Key Words—Termites, Isoptera, Rhinotermitidae, Prorhinotermes simplex, defense secretion, (E)-1-nitropentadecene, toxicity, Musca domestica, insecti- cide resistance. INTRODUCTION The defense of a termite colony that is carried out by the soldier caste is phyloge- netically an important feature enabling termites to survive, despite the fact, that they are a substantial part of the food chain for many animals, including preda- tory insects. Different defensive adaptations have evolved from simple biting to the production of toxic secretions. Chemical defense is typical for numerous genera of the family Rhinotermitidae (Deligne et al., 1981). The mandibulate *To whom correspondence should be addressed. 1This study is supported by the Grant Agency of Czech Republic, project #522/9710126. 657 0098-0331/99/0300-0657$16.00/0 © 1999 Plenum Publishing Corporation