H Y MEN OP TERA . 639 



larvae and pupae to their own nests, and bring them up with 

 their own, and they in turn work hard for their captors, and 

 take great interest in their welfare and success. When a 

 party of marauders comes back without any booty their 

 slaves give them a cold reception ; but if they come back- 

 laden with plenty of larvae and pupae, the slaves rush out 

 and meet them with apparent delight and exultation. 



Some species of slaveholders (e.g., Formica difficilis) 

 work side by side with their slaves. However, in one species 

 (Polyergus ruffscens of Europe) the masters have depended 

 upon their slaves so long that they cannot build their own 

 nests or feed themselves or care for their young, but have 

 only retained the power of fighting to get more slaves. 

 Hiiber tells of placing several of these slaveholders by 

 themselves, where nearly all helplessly starved, although 

 there was plenty of food all around them. Then a slave was 

 introduced, which at once set to work and made a nest and 

 fed those still alive, thus saving from death its stupid 

 masters. 



The classification of the ants is still in a very imperfect 

 state. Many of our common species are still undescribed, 

 and the limits of the families have not yet been determined. 

 But, if we except a few species found in Texas and Utah, 

 our described species represent only three families. These 

 can be separated by the following table : 



TABLE OF FAMILIES OF THE FORMICINA. 



A. Peduncle of the abdomen consisting of a single segment. 



B. Abdomen not constricted between the second and third seg- 

 ments (the first segment forms the peduncle), p. 64o..FoRMiciD/E. 

 BB. Abdomen constricted between the second and third segments. 



p. 642 PONERID.E. 



AA. Peduncle of the abdomen consisting of two segments, p. 642. 



MYRMICIDJE. 



