26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I4I 



lem of existence in the desert; in fact, symbiosis is a mode of life 

 adopted by nearly half of the desert cockroaches about which we have 

 any information. Vlasov and Miram (1937) iomid Poly phaga indica, 

 Polyphaga saussiirei, and Arenivaga roseni in the burrows of rodents 

 and desert turtles. In the desert regions of Arizona, females of 

 Arenivaga erratica were found commonly in burrows of the kangaroo 

 rat (Vorhies and Taylor, 1922) and in dens of wood rats and ground 

 squirrels (Ball et al., 1942). Arenivaga apacha and Arenivaga hol- 

 liana have also been found inhabiting the nests of wood rats (Hebard, 

 1917; 1943a). Bei-Bienko (1950) has suggested that the adaptation 

 of desert-inhabiting cockroaches to rodent burrows might enable 

 these insects to survive in the severe climatic conditions of deserts in 

 summer. 



Under desert conditions in southern Arizona, the relative humidity 

 outside of the burrows of the kangaroo rat is i to 15 percent during 

 the day and 15 to 40 percent at night ; but inside the burrows the rela- 

 tive humidity is 30 to 50 percent, and the temperature, even during 

 the day, is below 30° C. (Schmidt-Nielsen, 1949). Thus by living 

 in rodent burrows during the day and going outside at night, the desert 

 cockroaches could avail themselves of the most favorable micro- 

 climates obtainable. Presumably whatever food these insects eat pro- 

 vides them with sufficient water to enable them to survive under 

 desert conditions. Bodenheimer (1953) has suggested that the extent 

 of utilization of dew, which is sometimes heavy in the desert, should 

 be investigated; he stated that tenebrionid beetles have been seen in 

 the early morning eating dry [dead?] herbs that were still wet with 

 dew. It is obvious that there is a need for additional detailed informa- 

 tion without which we can only guess about the ecology of desert 

 cockroaches. 



In the following list we have cited only those species that were 

 stated to have been found under desert conditions. Undoubtedly, re- 

 lated species that have been taken in similar localities are also desert- 

 inhabiting forms, as, for example, other species of Arenivaga that 

 were collected in Texas by Hebard (1943a). In the absence of specific 

 information linking such other species with deserts, we have arbi- 

 trarily relegated those forms to the section on outdoor habitats. In 

 addition to the species listed below, desert cockroaches are said to be 

 found in the following genera : Anisogamia, M ononychohlatta, and 

 Nymphytria (Chopard, 1938). 



