90 INSECTS AND HUMAN WELFARE 



Mosquitoes are very important from the standpoint of 

 disease and have been referred to in considerable detail in a 

 previous chapter. A few species may be regarded as truly 

 domestic or household insects. Thus the house mosquito, 

 Culex pipiens, native to Europe, but now widespread in the 

 temperate northern regions of both hemispheres almost al- 

 ways breeds in close proximity to dwellings. The larvae occur 

 abundantly in rain barrels, cisterns and similar receptacles, 

 and the adults enter houses with unusual persistence. In trop- 

 ical countries, the same is true of the yellow-fever mosquito 

 (Stegomyia fasci-ata) and the Filaria mosquito (Culex quin- 

 quefasciatus) , both of which are truly domestic forms. Many 

 other kinds of mosquitoes, especially the malarial forms 

 readily venture indoors, but this habit is much more pro- 

 nounced and constant in the case of the ones first mentioned. 



Several species of cockroaches or roaches have become 

 closely associated with man and are now widely distributed 

 throughout the world. These insects are particularly inter- 

 esting in this respect as they belong to a group of insects of 

 very primitive character which has existed with little change 

 over long geological periods. One would not, therefore, ex- 

 pect to find the numerous present-day cockroaches very 

 adaptive or versatile in their behavior. Nevertheless, several 

 species have cast their lot with man, since his advent, and 

 have followed him in his wanderings. One of these, the small 

 so-called German roach (Blatella germanica), is especially 

 widespread and abundant in the cooler parts of the northern 

 hemisphere. In spite of its name, its association with man- 

 kind probably antedates the race to which it has been re- 

 ferred. From its probable home in the far-east it has spread 

 westward and reached America only at a very recent date. 

 It was first noticed by the residents of New York City at the 

 time the Croton aqueduct was put into operation, and was 

 called by them the Croton bug on the belief that it had come 

 with the water supply. This was a natural supposition as 

 these warmth-loving insects congregate in proximity to hot- 

 water pipes or in warm or humid kitchens. The Croton bug 



