98 PROC. ENT. SOC. WASH., VOL. 21, NO. 5, MAY, 1919 



inhabiting and occur in the same regions (except R. tlavipes). 

 There are apparently no differences in the prothoracic tibiae 

 of workers of species of Reticulitermes that occur in the arid 

 West from those of the humid eastern portions of the United 

 States. 



If all termite workers living in the hard, dry soil of the arid 

 southwestern regions were modified like the five species above 

 described, this might seem good evidence in favor of the view 

 that the enlarged segments are the result of use or of response to 

 the environment. It is, however, not true that the prothoracic 

 tibiae are modified in all termite species inhabiting the earth of arid 

 regions. The workers of Constrictotermes cinereus Buckley and 

 C. tenuirostris Desn., living in similar earth burrows in the same 

 dry regions of the Southwest, have the prothoracic tibiae scarcely 

 at all, or very slightly, larger than those of the mesothoracic 

 legs. Further, in workers of the genus Reticulitermes the pro- 

 thorcic tibiae are very slightly enlarged, and there are apparently 

 no differences in this respect between species of this genus living 

 in the earth of arid western areas and other species from humid 

 eastern sections of the United States. 



Since the two species of Constrictotermes and certain species of 

 Reticulitermes live in arid areas, and use their legs for digging 

 in hard earth, but have not acquired prothoracic tibiae of the 

 sub-fossorial type which is found in the five species of Amitermes 

 and Anoplotermes, it is obvious that the cause of the enlargement 

 is neither the factor of use nor of response to environment, but 

 is rather the survival of chance variations which were adapted to 

 their environment. One is tempted to go a step farther in stating 

 that the constant, non-fluctuating character of the prothoracic 

 enlargements in each species points to its origin as a discontinuous 

 variation. 



In the Scarabaeidae, the sacred beetle (Ateuchus sacer, Linn.) 

 lacks tarsi on the front legs in both pupae and adults and has 

 greatly modified tibiae especially adapted for digging, which 

 must be of great aid in its digging operations. In other Scara- 

 baeidae, species of Geotrupes, which make even deeper excavations 

 in the earth, tarsi are present on the front legs. Fabre (1918) 

 concludes that, in case of the sacred scarab, the absence of the 

 tarsi on the front legs can not be a loss as a result of the digging- 

 transmitted to posterity. 



"The workers of Anoplotermes fumosus are very characteristic 

 and odd in appearance. They are of a dirty grey color and have a 

 rather elongate, fusiform or bag-shaped body; the habit of crawling 

 about in single file, closely following one another, is especially 

 characteristic. 



