BIOTIC ASSOCIATIONS OF COCKROACHES — ROTH & WILLIS yi 



oriental origin; and Leurolestes pallidus was endemic in the West 

 Indies (Rehn, 1945). Princis (1954a) rejected Africa as the original 

 home of Blatta orientalis and advanced reasons for placing its origin 

 in Central Asia. 



Several domiciliary species have become well established in tem- 

 perate zones and some even in the Arctic. Bei-Bienko (1950) Usted 

 the following 10 species as sinanthropes in the Palearctic zone: Blatta 

 lateralis, B. orientalis, Blattella germanica, Leucophaea maderae, Peri- 

 planeta americana, P. australasiae , Polyphaga saussurei, Pycnoscelus 

 surinamensis, and Supella siipellectiliuin. In the warmer parts of the 

 temperate regions, as in their native Tropics, certain domiciliary- 

 species breed outdoors as well as indoors. In the less temperate 

 extensions of their ranges most domiciliary species are nearly always 

 found indoors. In regions with low winter temperatures these cock- 

 roaches do not survive in unheated structures ; but in heated buildings 

 Blattella germanica, for example, has been able to withstand the 

 rigorous climate of Alaska, where it has caused severe infestations 

 (Chamberlin, 1949). 



The limiting factors that determine whether man-made structures 

 will provide suitable habitats for cockroaches are favorable tempera- 

 ture and availability of water and food. The range of temperatures 

 that man provides for his own comfort and protection fosters the rapid 

 increase of cockroach populations indoors. Gunn (1934, 1935) has 

 demonstrated that the preferred temperature range (zone of indif- 

 ference) of Blatta orientalis is 20-29° C. The upper limit of the pre- 

 ferred temperature of Blattella germanica and Periplaneta atnericana 

 is 33° C. (Gunn, 1935). The lower limits of temperature tolerance 

 were not sharply defined in Gunn's work. However, less than optimum 

 temperatures, if they last for only short periods, are not necessarily 

 lethal. The 24-hour mortality for P. americana that had been held for 

 one hour at 0° C. was only 2±2 percent (Knipling and Sullivan, 

 1957). Gunn (1934) observed that Blatta orientalis would not settle 

 at temperatures above 33° C. and would react violently against higher 

 temperatures (e.g., 39° C.) by running away; thus the thermotactic 

 behavior of cockroaches might be presumed to bring them into favor- 

 able environments within structures. Thermal death points have been 

 determined for the above three species by Gunn and Notley (1936). 



It is common knowledge among those who rear cockroaches experi- 

 mentally that, unless the water content of the food is high, fluid water 

 is essential in the insects' dietary. Ten species of domiciliary cock- 

 roaches have been shown to be unable to survive as long on dry food 

 alone as they could on food and water at 36-40 percent relative 



