BIOTIC ASSOCIATIONS OF COCKROACHES — ROTH & WILLIS 25 



Pycnoscelus surinamensis 

 Texas. — In the nests of wood rats, Neotoma sp. (Hebard, 1917). 



DESERT HABITATS 



There is relatively little ecological information about cockroaches 

 that live in deserts, even though certain species, notably Polyphaga 

 aegyptiaca, have long been known to inhabit arid zones. In fact, so 

 little is known about the ecology of arid-zone insects in general that it 

 is more a subject for research than for review (Pradhan, 1957). In 

 their account of the cockroaches of Northern Kenya and Jubaland, 

 Kevan and Chopard (1954) describe in some detail the vegetational 

 areas of this arid desert or semidesert country, which averages only 

 about 10 inches of rain per year. The other sources that are cited 

 below contain very little more biological information than the ab- 

 stracted material that is given under each species. 



Nearly all the Polyphaginae are said to be marked xerophiles whose 

 distribution coincides with that of the deserts (Bei-Bienko, 1950), 

 With the exception of Arenivaga floridana, the species of Polyphagi- 

 nae in the United States all occur in the Southwest, where they are 

 (with a few exceptions) the only cockroaches that inhabit the desert 

 regions proper (Hebard, 1917). The Polyphaginae reach their 

 greatest diversity in the deserts of Northern Africa and Anterior and 

 South-Central Asia (Bei-Bienko, 1950). Some of the desert-inhabit- 

 ing species have also been found under nondesert conditions. This 

 only further exemplifies the plasticity of cockroaches in adapting to 

 different environments. 



The ability of desert insects to live under what appear to be ex- 

 tremely unfavorable conditions has been abundantly illustrated by 

 Pradhan (1957) . Uvarov (1954) has pointed out that a desert "covers 

 a great variety of landscapes, which provide desert animals with a wide 

 range of habitats, some of them offering very favorable conditions 

 for life." Pradhan (1957) stated that many desert animals avoid 

 the extremes of desert climates by choosing suitable microclimates for 

 diurnal resting places, that a permanent or temporary underground 

 existence is very common among insects in arid zones, and that many 

 nocturnal Orthoptera burrow into the soil or hide under stones where 

 temperatures are lower. For example, the type of Parcoblatta desertae 

 was found under a boulder on the bare desert (Rehn and Hebard, 

 1909). 



Symbiosis with burrowing animals is another solution to the prob- 



