172 NATURAL ARRANGEMENT OP INSECTS. 



It is within the tropics that these insects chiefly abound, 

 and where they are excessively destructive ; and nothing 

 seems efficiently protective against their incursions. The 

 group has been divided according to the structure of the 

 abdomen ; which in some has but one node only to its 

 peduncle, but in others it has two. It is in the first 

 division that we find the stingless genera, namely, For- 

 mica Linn., Formicina Shkd., Polyergus Latr., PolyrhcL- 

 chis Shkd., and Dolichoderus Lund, besides several other 

 yetuncharacterised genera, which we shall shortly publish. 

 (155.) The Formicina rufa, or horse ant, forms those 

 large nests of dry leaves and sticks we so frequently ob- 

 serve in the woods ; and within these nests two genera 

 of Staphylini appear to be parasitical — Lomechusa and 

 Fella; and in their deepest recesses innumerable wood- 

 lice (Onisci) are constantly found. The nature of the 

 connection between these insects has not yet been ascer- 

 tained, but perhaps it may be analogous to what has 

 been observed between other species and the Aphides. 

 It has been said that the larva of Cistela lepturoides also 

 lives in the nest of this species. Another singular Sta- 

 phylinus (the minute Claviger), which is totally blind, 

 and otherwise remarkable in structure, inhabits the nests 

 of the Formicina flava, where it has once been dis- 

 covered in this country. Some of the species and genera 

 of this tribe, it is said, exclusively of the FormicidcB, 

 seek in the nests of other species, but always of the same 

 tribe, the auxiliaries, upon which they impose all the 

 " out-door " labours of the community ; but it is the 

 genus Polyergus which is most distinguished for its sub- 

 jugation of " helots," or " slaves." Cercopis and Mem- 

 bracis, two genera of Hemiptera, supply the place of 

 the " Cow Aphis " to the Brazilian genus Dolichoderus. 

 All the FormicidcB are extremely pugnacious, and fight 

 with inveterate obstinacy ; and frequently issue from 

 their nests in close columns, for the purpose of attacking 

 neighbouring colonies; this, of course, with variable suc- 

 cess, but great slaughter is always made. Odontomachus 

 constitutes the transition from the stingless to the acu- 



