BIOTIC ASSOCIATIONS OF COCKROACHES— ROTH & WILLIS 343 



seemed to have overcome the American which had been more numer- 

 ous in former years. 



In conclusion, we emphasize that many of the above observations 

 are merely tentative impressions gathered by workers who have 

 watched many species of cockroaches in nature. Obviously, additional 

 observations coupled with appropriate experimentation will be needed 

 to disclose the true structure of each presumed association and to re- 

 solve apparent discrepancies. Although we are greatly indebted to 

 the cited authors for their contributions to the known information, 

 we anticipate that future results of cleverly designed laboratory ex- 

 periments will do much to dispel the uncertainty that still surrounds 

 our knowledge of the relations of the Blattaria to each other. 



XVIII. DEFENSE OF COCKROACHES AGAINST 

 PREDATORS 



Irritating or repellent secretions provide many animals belonging 

 to widely unrelated groups with a more or less potent means of 

 defence . . . 



It will be seen that this method of defence does not rest merely 

 upon a passive unpalatable attribute, but upon an active emission 

 of the unpalatable substance which, since it occurs when the 

 animal is seized or threatened by an enemy, enforces its effective- 

 ness. In its highest development we find different forms whose 

 specialized habits and modified structure enables them to project 

 secretion at the enemy, and thus to discourage attack. 



CoTT (1940) 



There are very few records indicating that cockroaches are unac- 

 cepted as food by other animals. Hutson (1943) found that the duck, 

 guinea fowl, and pigeon would not normally eat Pycnoscelus surina- 

 mensis, and in his experiments with the chicken eye worm he had to 

 force-feed his birds with infected cockroaches. Lederer (1952) 

 found that insectivorous birds in the Zoological Garden, Frankfurt 

 am Main, either refused hardened (as opposed to teneral) American 

 cockroaches or ate them unwillingly. Carpenter (1925) reported that 

 a monkey (Cercopithecus) failed to feed on cockroaches and sug- 

 gested that the insects' odor made them repugnant ; however, there 

 are a number of positive records of monkeys feeding on cockroaches 

 (see pp. 284-286). 



Cockroaches may escape capture by predators through evasive be- 

 havior, concealment, protective coloration, mimicry, or secretion of 

 malodorous materials. Nocturnal cockroaches may avoid predators 

 that are active during the day (Crawford, I934), but nocturnal pred- 

 ators are apparently quite successful in capturing cockroaches. Some 



