382 NATURAL HISTORY. 



Ants in search of a similar arrangement, and found in Ponira distinctly developed stridnlant organs of 

 the same type as in Mutilla, and capable also of producing sounds perceptible by the human ear. 



The Formicidse may be usefully divided into two great groups, namely, the Forrnicinse, so named 

 from the typical genus Formica, in which the abdominal petiole has only a single knot, or scale ; 

 and the Myrmicinse, including the great genus Myrmica and its allies, which have two knots, or 

 scales, on the petiole. Of British species of the former group, we have already referred to several, 

 such as the Great Wood Ant, the Warrior Ant, the Jet Ant, &c. The WOOD ANT (Formica rufa), 

 which is an exceedingly abundant species, has the head and thorax of a rusty-red colour, with a 

 brownish-black tinge in parts, while the legs and abdomen are almost entirely of the latter colour. 

 The largest workers measure more than a quarter of an inch in length, and the females as much as 

 five lines. This species is found in woods, where it lives in a great heap of vegetable 

 fragments, portions of wood and leaves, small sticks, and the needles of pine trees, beneath 

 which the nest is continued in a great extent of subterranean passages and chambers. In 

 favourable situations these nests attain great dimensions : they may be found more than six 

 feet in diameter, and four or five feet high. Like the other species of the genus, this Ant 

 possesses no sting, but the glands producing the acid secretion are well developed, and it appears 

 to be used not only by injection into wounds inflicted by the mandibles, but also by being ejected, 

 after the fashion of that of the Bombardier Beetles, for the purpose of keeping an enemy at a 

 distance. The WARRIOR ANT (Formica sanguinea} is less common in England than the preceding 

 species. It has the head and thorax of a blood-red colour, instead of rusty-red, and the legs are red. 

 The largest workers attain a length of a third of an inch. Its communities are smaller than those 

 of the Wood Ant, and its nest is frequently constructed in banks. Its habit of making slaves has 

 already been alluded to. The Wood Ant seems to inhabit the greater part of the Northern 

 Hemisphere, and other European species are widely distributed. Other regions, however, have their 

 own peculiar species, and they are particularly abundant in tropical countries, where also they attain 

 a larger size. One of the largest species is the GIANT ANT (Formica gigas] of the East Indies, of 

 which the female measures an inch long. Some of the species of a nearly-related Indian genus 

 (Poli/rhachis) are remarkable for making a curious little nest in a curious situation. Mr. T. C. 

 Jerdon, speaking of one of them (P. nidificans), says : " This Ant makes a small nest about half 



an inch, or rather more, in. 

 diameter, of some papy- 

 raceous material, which it 

 fixes on a leaf. I have 

 opened two, each of which 

 contained one female and 

 eight or ten workers." 



A very singular species 

 of this group, of which only 

 workers are known, is a 

 MVHMECOCYSTUS MExicANus (Natural size and Magnified). Mexican insect, described 



under the name of Myrme- 



cocystus mexicanus. The workers are of two forms namely, ordinary Formicine small workers, 

 which appear to perform the labours of the community ; and a larger form, to the peculiarities of 

 which the name of the genus refers, in which the abdomen is greatly inflated and nearly transparent, 

 but bears upon its -surface horny plates, indicative of the segments. These peculiar workers, which 

 are very inactive, seem to have as their sole duty the secretion of a peculiar kind of honey, which they 

 are said to discharge into receptacles. 



The genus Ponera and its allies, in which the petiole still has only one knot, but the females and 

 workers are armed with stings, include many species of larger size than those hitherto referred to. 

 They are mostly inhabitants of tropical countries, and their history is very imperfectly known. To 

 this group belong the DRIVER ANTS, or VISITING ANTS, of West Africa, generally referred to the 

 species Anomrna arcens, although many entomologists are of opinion that other Ants may have the 

 same habits. The workers of Anomma arcens grow to a length of nearly half an inch, and are 



