BIOTIC ASSOCIATIONS OF COCKROACHES — ROTH & WILLIS 345 



certain enemies. But this does not necessarily imply that they are not 

 on the whole beneficial to the species attacked." Certain cockroach 

 secretions may well be repellent to many predators, but as this is a 

 purely negative aspect of the predator-prey relationship little thus far 

 has been observed or published. Potential prey that successfully de- 

 fends itself against attack is never found in a predator's stomach. 



Cockroaches have a variety of glands which secrete odorous ma- 

 terials. Certain secretions, produced by tergal or dorsal glands in 

 males, are involved in sexual behavior ; the females feed on the secre- 

 tion from these glands prior to copulating (Roth and Willis, 1954). 

 However, other secretions which are produced by both sexes are 

 ejected or given off when the insect is disturbed ; undoubtedly these 

 are defensive weapons that are used against predators. Very few 

 experiments or observations are on record to show how effective these 

 secretions may be in protecting the cockroach. Although the mor- 

 phology of some of the glands has been described, relatively little is 

 known about the chemistry of their secretions. 



Many species of Australian cockroaches have been reported to 

 emit "disgusting" odors, though the glands producing these secretions 

 have not been described, nor is the chemistry of the compounds known. 

 Cosuwzosteria lateralis exposed two orange-red spots on the abdomen 

 while emitting a pungent odor which deterred a collector from 

 capturing it (Shelford, 1912). Another Australian species, Platy- 

 sostcria castanca, when disturbed on barren ground tilts forward on 

 the vertex and straddles out the posterior legs, supporting itself in a 

 vertical position on the head and tarsi ; in assuming this attitude it 

 will squirt a foetid fluid as a fine spray for a distance of 6 or 7 inches 

 (Shaw, 1914). Spencer (1892) mentions the pungent odor given off 

 by a cockroach which had been accidentally cut in two. Rageau 

 (1956) stated that in the New Hebrides and New Caledonia Cufilia 

 nitida emits, when disturbed, a corrosive liquid with an extremely dis- 

 agreeable odor. 



The adults of Eurycotis floridana emit an odorous fluid when 

 seized (Rehn and Hebard, 1905). The fluid, which may irritate 

 sensitive skin areas, may be ejected as a spray for a distance of several 

 inches. This secretion has been identified as 2-hexenal (Roth et al., 

 1956), and the ventral abdominal glands which produce it have been 

 described (Stay, 1957). Eisner (personal communication, 1958) has 

 found that the toad Bnfo marinus and the frog Rana pipicus in- 

 variably spit out adults of £. floridana which they have seized. The 

 odor of 2-hexenal was strongly apparent after these attacks, and the 

 insect was never damaged. However, the lizard Anolis equestris 



