280 AN INTRODUCTION TO ENTOMOLOGY 



the individuals that are fed; the feeding of the young and the queens 

 being accompanied by a licking of their bodies by the nurses. 



Among the more important papers on this subject are one on 

 termites by Holmgren ('09) and one on ants by Wheeler ('18). 

 Holmgren shows that all of the castes of termites, but especially the 

 queens, have extensive exudate tissues, consisting of the peripheral 

 layers of the abdominal fat-body, the products of which pass through 

 pores in the cuticula, where they are licked up by other members ' . 

 the colony; and that the intensity of the licking and feeding of ^ e 

 individuals of a termite colony is directly proportional to the amount 

 of their exudate tissue. Wheeler in his paper on ants shows that the 

 larvae of certain species of ants possess remarkable exudate organs, 

 and proposes for this exchange of nourishment the term trophallaxis* 



It is believed by the writers quoted above and by others that this 

 exchange of nourishment between those individuals that feed and 

 those that are fed was the source of the colonial habit in social insects. 

 Roubaud ('16) in a paper on the wasps of Africa points out the 

 probable steps by which the social habit was developed in wasps. 

 Beginning with certain solitary eumenids that feed their larvae from 

 day to day and while doing this feed upon saliva exuded by the larvae, 

 he suggests that there naturally follows a tendency to increase the 

 number of larvae to be reared simultaneously in order at the same 

 time to satisfy the urgency of oviposition and to profit by the greater 

 abundance of the secretion of the larvae. 



Now that this explanation of the origin of the social habit has 

 been suggested, it, doubtless, will be much discussed. The student is 

 urged, therefore, to consult the current literature for opinions regard- 

 ing it. 



The most extended account of the termites of this country is the 

 recently published paper by Nathan Banks and Thomas E. Snyder 

 ('20). In the first part of this paper, Mr. Banks gives a revision of 

 the nearctic termites, in which all of our kno\vn species are described, 

 seventeen of them for the first time. This brings the total number 

 of our known species up to thirty-sLx, representing ten genera. 



In the second part of this paper, Mr. Snyder brings together the 

 known data regarding the habits and distribution of the termites of 

 the United States; much of which data is based on his personal 

 observations. 



Many species of insects live in the nests of termites. The relations 

 of the termitophiles, of which several hundred species have been 

 described, to their hosts vary greatly; some are predatory, some are 

 parasites, and others are guests. Among the guests some are indiffer- 

 ently tolerated, while others are true guests which produce exudates 

 that are eagerly devoured by their hosts and in return either receive 

 regurgitated food or manage to prey on the defenseless brood. 

 Among the termitophiles are some that are very remarkable in form, 

 having the abdomen excessively enlarged and being furnished with 

 large exudate organs. 



*Trophallaxis : trophe {Tpo<pri), nourishment; allattein {dWdrTeiv), to exchange. 



