PROCEEDINGS OF THE 



ENTOMOLOGICAL SOCIETY OF WASHINGTON 



VOL. 21 MAY, 1919 No. 5 



SOME SIGNIFICANT STRUCTURAL MODIFICATIONS IN NEARCTIC 



TERMITES. 



BY T. E. SNYDER, Bureau of Entomology. 

 Introduction. 



Certain facts in the biology of Nearctic termites and details 

 of their structure appear to indicate adaptation to their environ- 

 ment. The question as to whether such structural peculiarities 

 have appeared as the result of use or as chance variations which 

 have survived through adaptation to their surroundings, has 

 long been discussed, but it is believed that these observations 

 may furnish evidence which is important from an evolutionary 

 standpoint. 



Modified Prothoracic Tibiae of Workers. 



The workers of some species of earth-inhabiting (subterranean) 

 termites which occur in the southwestern states and Mexico 

 have sub-fossorial prothoracic tibiae. The tibiae of the prothoracic 

 legs are enlarged, /. e., somewhat swollen or sub-fusiform and 

 spinose (Plate I). However, while there is a contrast between 

 the pro- and meso-thoracic tibiae, the legs on the whole are not 

 greatly modified. 



The prothoracic tibiae are used in digging and in the semi- 

 arid regions where these termites occur the soil often becomes dry 

 and remains caked hard for long periods of drought. 



Species with the tibiae of the prothoracic legs enlarged or sub- 

 fusiform are Amitcmies tubiformans Buckley, Awitermcs n. sp. a, 

 A. wheeleri Desn., Amitermes n. sp. c, and Anoplotermes fumosus 

 Hag. In Anoplotermes fnnwsits the widened, flattened shape of 

 the tibiae and tarsi give the leg a peculiar short and stubby ap- 

 pearance. In addition, at the extremity of the prothoracic 

 tibiae there is a chitinized area on the dorsal surface. 



The pro- and meso-thoracic tibiae of workers of ( 'onstrictotermes 

 tcnnirostris Desn., C. cincrciis Buckley, l\cticitlitcrmcs 'lai'ipes 

 Kol., and other species of the genus Rcticiilitcrmcs Holmg. are not 

 in such marked contrast although the species are also earth- 



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