336 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I4I 



species are indications of gregariousness. However, until gregarious- 

 ness has been proved experimentally for each species, we concede that 

 reactions to environmental stimuli might be sufficient to bring about 

 some of the observed groupings without any interaction between in- 

 dividuals. 



In concluding this section we note that Tepper (1893) stated that 

 carnivorous cockroaches in Australia lead more or less solitary lives, 

 and that one rarely meets several together in close proximity. Taka- 

 hashi (1940) observed that in Formosa Blattella humbertiana does 

 not have a tendency to throng together. Rau (1947) stated that the 

 adults of Ischnoptera deropeltiformis showed no tendency toward 

 gregariousness, but in the laboratory newly hatched young lived close 

 together under bark and remained together throughout the nymphal 

 stages. We wonder whether this gregariousness was not imposed by 

 the restricted quarters of the cage. As mentioned above. Dowdy 

 (1955) did not find Parcoblatta sp. to be gregarious in the field. 



INTRASPECIES FIGHTING 



Fighting occurs among cockroaches of the same species over food 

 or shelter or between males. Saupe (1928) observed late-instar 

 nymphs of Blaberus craniifer attack each other and even adults. Ad- 

 ditional records cited in the section on intraspecies predation (p. 322) 

 imply fighting within a species. Rau (1924) saw a male of Blatta 

 orientalis attack another male in copula and bite away a large portion 

 of its wing. Two other males in the container had their wings badly 

 torn overnight, presumably as a result of fighting. 



Ehrlich (1943) stated that individuals of Periplaneta americana 

 that are feeding will ward off intruders by spreading their wings and 

 pushing with their hind legs. However, the intruder will approach 

 again and again biting the feeder in the legs and wings. Frequently 

 the odor of approaching food was sufficient to cause the cockroaches 

 to fight and bite each other. Biting and fighting also occurred when 

 individuals of this species defended their daytime hiding places. A 

 position of attack is assumed when two antagonistic individuals of 

 P. americana meet (Ehrlich, 1943, fig. 14). The insects raise their 

 bodies slightly above the ground, by extending their legs, and they 

 stretch their heads forward horizontally so that their mouth parts 

 protrude ; when the insects jump at each other, they may wound each 

 other severely in the soft parts of the body. Fighting between sexually 

 excited males resulted in injury to their legs, wings, cerci, and other 

 parts of the body. Frequently an insect that could no longer defend 



