INTERRELATIONS OF INSECTS 279 



true kings and queens, with functional wings or their remnants; second 

 form, substitute males or females, with short wing pads; third form } 

 ergatoid, or worker-like, males or females, without wings, this type 

 being rather rare. 



In certain tropical species there are two types of soldiers, and two of 

 workers; so that adults of either sex may occur under seven different 

 forms in the same colony. 



Origin of Castes. Grassi maintains that all the forms are alike at 

 birth except as regards sex, and that the differences between worker 

 and soldier, which are independent of sex, depend probably upon nutri- 

 tion. Grassi attributes all the diversities of caste, except the sexual 

 ones, to the character and amount of the food. 



C. B. Thompson states that at hatching there are two kinds of 

 nymphs (i) the "reproductive," which develop into the fertile castes, 

 and* (2) the " worker-soldier" nymphs, which become the sterile castes; 

 these two types being distinguishable by internal differences in the brain, 

 compound eyes, and sex organs. 



Food. The food of termites is of six kinds: (i) wood; (2) matter 

 emitted from the oesophagus or rectum, termed respectively stomodaeal 

 and proctodaeal food; (3) cast skins and other exu vial stuff; (4) the bodies 

 of their companions; (5) saliva; (6) water. Of these the proctodaeal 

 food is the favorite. Nymphs receive at first only saliva; later they get 

 stomodaeal and proctodaeal food until, finally, they are able to eat wood 

 the staple food of a termite. 



American Species. Our common termite is Reticulitermes flavipes, 

 which occurs throughout the United States, excavating its galleries in 

 decaying logs, stumps or other dead wood. The nuptial flight of this 

 species takes place in spring, when the two sexes swarm in numbers that 

 are sometimes enormous. One swarm, as recorded by Hagen, appeared 

 as a dense cloud, and was being followed and attacked by no less than 

 fifteen species of birds, among which were robins, bluebirds and sparrows ; 

 some of the robins were so gorged to the mouth with termites that their 

 beaks stood open. Though plenty of winged females are said to occur 

 in the swarming season, the true queen of R. flavipes is extremely rare, 

 the queen usually found being evidently, from her undeveloped wings, 

 a substitute queen. 



The European species Reticulitermes lucijugus has been found 

 recently in Massachusetts. Most species of termites occur in warm 

 climates, however. North of Mexico thirty-six species are known, 



