NO. 7 PROTECTIVE ADAPTATIONS — McATEE 39 



species live chiefly in structures of man hence have little relation to 

 the indigenous fauna. 



Bird enemies.- — Thirty-six species of hirds share the 117 identifica- 

 tions of roaches in the food of nearctic birds. The number of records 

 was 10 or more in the case of four species of birds, and the number 

 of specimens eaten was as high as 10 in two instances but usually 

 was less. 



Percentage of identifications among those of all insects, .0613 ; 

 percentage of species in this group among the whole number of insect 

 species known, .3123. 



Other enemies. — Roaches seem to be more or less regularly eaten 

 by toads, frogs, the armadillo, spiders, rats, scorpions, and wasps. 

 They have specific parasites among the Evaniidae. 



Discussion. — Owing to the poverty of the roach fauna of the United 

 States, research here is not likely to throw much light on relations of 

 these insects and their adaptations to predators. Tropical species are 

 said to resemble various other organisms, including isopods, myrio- 

 pods, longicorn, and coccinellid beetles, and hemiptera of the family 

 Miridae. But since all of these models themselves are freely eaten 

 by predators, the significance of the resemblances is hardly that usually 

 attributed. In the United States natural enemies would seem to l)e 

 proportional to the scanty population of native roaches. 



DICTYOPTERA (mANTIDS) 



Like the roaches, the mantids of the United States are few in 

 number and do not exhibit the unusual modifications displayed by 

 some of the tropical representatives of the grouj). The principal 

 defenses of our species must be their comparatively large size among 

 insects and their highly predatory nature. However, these character- 

 istics are of little avail against still larger predators and we find these 

 insects taken by birds in numbers probably bearing no distant relation 

 to the frequency of mantids in the country. Number of identifica- 

 tions, 58 ; percentage of identifications among those of all insects, 

 .0304 ; percentage of species in this group among all insect species, 

 .2082 (for the world, of course). The number of species of birds 

 concerned in the records here cited is 21. Mantids are eaten also 

 by lizards. 



CORRODENTIA (PSOCIDS) 



The Psocidae, which include the booklice seen in houses, are 

 delicate and minute insects. Many of the out-of-door species are 

 winged and the wings bear color patterns which may assimilate the 



