92 BRITISH ANTS. 



complete segments and well -developed genitalia, the right side has only six 

 complete segments, and a membranous incomplete seventh. The genitalia 

 are imperfect, the volsella being represented only by a piece corresponding 

 to its dorsal portion and the stipes is wanting. The legs are female, except 

 the left fore leg, which is male, with a pectinate strigil. 



2. Male on left, female on right, resembling the preceding, but with the 

 dark female colour more pronounced on the male side of the head. Wings 

 well developed on both sides, thorax female, though dark on the right and 

 pale on the left, except the epinotum which is entirely greyish yellow. Abdo- 

 men almost typically male in colour and form, with the genitalia well- 

 developed on both sides, but with a feeble mid-dorsal impression. Legs 

 female, except the left fore one, which is shorter and thicker as in the male, 

 with strigil cleft but not pectinate. 



The most interesting problems connected with Anergates are, 

 how the female gets accepted by a Tetramorium colony, and why 

 there are only workers of the latter present in such colonies. It is 

 evident that the female must enter a Tetramorium nest in some 

 way, and be accepted by the workers, when the latter must kill 

 their own queen, or males and winged females if present, since the 

 Anergates female can hardly be strong enough to accomplish this 

 herself. Anergates colonies are everywhere exceedingly scarce and 

 difficult to find, whereas the host species is generally abundant and 

 common where it occurs, and this evidently indicates that the 

 founding of an Anergates colony is by no means a simple matter. 

 Since Anergates is absolutely dependent on the Tetramorium 

 workers, and no more of these can be produced, a colony can 

 only last for the length of the life of the hosts. 



Forel, Avebury, and Wasmann express the view that Anergates 

 is descended from a slave-making species, and on this point Lord 

 Avebury 7 writes : " In Anergates, finally, we come to the last 

 scene of this sad history. We may safely conclude that in distant 

 times their ancestors lived, as so many ants do now, partly by 

 hunting, partly on honey ; that by degrees they became bold 

 marauders, and gradually took to keeping slaves ; that for a time 

 they maintained their strength and agility, though losing by 

 degrees their real independence, their arts, and even many of their 

 instincts ; that gradually even their bodily force dwindled away 

 under the enervating influence to which they had subjected them- 

 selves, until they sank to their present degraded condition weak 

 in body and mind, few in numbers, and apparently nearly extinct, 

 the miserable representatives of far superior ancestors, maintain- 

 ing a precarious existence as contemptible parasites of their former 

 slaves." 



There is nothing in the structure however of this permanent 

 social parasite to prove that it is descended from a slave-making 

 species, and it seems more probable, as pointed out by Wheeler 19 , 

 that it is derived from a temporary parasite, or a guest ant, per- 

 manently attached to the nest of another species. Emery believes 

 that Anergates is descended from Monomorium, and that it, or it s 



