98 Mr. Smith's Essay on the Genera and 



accidental visitors ; but that many are in some way highly neces- 

 sary, or highly conducive to some important point in the economy 

 of the Formicarium, is, I think, easily proved. In the first place, 

 1 would mention the presence of Aphides in the nests of Formica 

 Jlava : of these I have observed great numbers in some colonies, 

 they are kept usually apart from the full-grown larvae and pupae, 

 and are eagerly carried off by the Ants, when exposed by the re- 

 moval of a part of the Ant-hill, or, as may be better observed, by 

 the removal of a stone, when the nest is constructed beneath ; it 

 was in the latter situation that I first discovered Clav'iger foveolata, 

 in 1844, in considerable numbers in the channels or galleries of 

 the Form'icarhun, the Claviger was quickly seized upon by the 

 Ants, and carried down into the subterranean labyrintlis. 



I have also obtained considerable numbers of insects which are 

 imprisoned by Ants, by watching Ant-hills in the spring, and ob- 

 serving all that is carried to them by the Ants : I have secured 

 numbers oi JMyrmedonia canaliculata, — Umhata and humeralis, and 

 also of Lomechusa emarginata ; the latter insect is found some- 

 times in the nests o£ F. fiisca, and F. rufa, but it is usually much 

 more abundant in the nests of Myrmica. In the nest of a species 

 of the latter genus I found a specimen of Batrisusformicar'ms, in 

 Yorkshire. Many other insects will no doubt be met with in 

 nests of Form'ictdce ; I have only mentioned such as I have seen 

 conveyed there by the Ants themselves, these being doubtless 

 highly beneficial in working out some important phase in their 

 economy ; and it has probably occurred to others as well as to 

 myself, that the aliment obtained from these insects may have 

 some stimulating properties, highly conducive to the development 

 of the sexes — but this point requires careful investigation ; I 

 would observe, however, as bearing upon this supposition, that I 

 never observed an Ant conveying these insects subsequent to the 

 development of tlie males and females. There is another insect, 

 which belongs, I believe, to the order Homoptera — Dorthesia 

 cataphracta — which is constantly found in most of the nests of the 

 Formicidce ; these have frequently been mistaken for the young of 

 Oniscus, which they greatly resemble in form, but are of a dif- 

 ferent colour, being snow-white : whether the presence of these 

 insects is in any way conducive to the development of any por- 

 tion of their economy, I am not prepared to advance an opinion 

 upon, but I have usually observed them in all the nests of the 

 Formicidce. 



The Formicidce, as a group, may be characterized as social 



