ACULEATE UYMENOPTEKA AND ICIINETJMONID^. 291 



openings below ; P. Busiris, a very similar nest to the last, but 

 about half the size ; P. Dolomedes, a small, oval, papery nest 

 on a leaf; and P. paromalus, whose nest, on a tree, consisted of 

 only two small cells of papery matter about an inch in diameter, 

 each cell with a separate opening. These four nests were found 

 in the island of Ceram. A very large number of the species 

 which I collected were found wandering about foliage or trunks 

 and on the ground ; and very often single specimens only were 

 obtained. The general characteristics of these ants appear to be, 

 that they live in small communities in exposed situations, and are 

 not very active ; while, being of generally large size, they must 

 be very much exposed to the attacks of insectivorous birds and 

 other animals. They have neither sting nor powerful jaws to 

 defend themselves, and, from their limited powers of increase, 

 would seem to be peculiarly liable to extermination, without some 

 special protection. It seems probable that this is the purpose 

 of the curious hooks, spines, and points with which they are 

 armed, and which must no doubt render them unpalatable morsels, 

 very liable to stick in the throats of their captors. The great 

 number of species of ants, and the curious modifications found 

 among them, indicate that they have much inherent tendency to 

 variation ; and we may well imagine how, in the severe struggle for 

 existence which is for ever going on where life is so abundant 

 and varied as in the tropics, the most widely distinct modifica- 

 tions have been seized upon by " natural selection " as a means 

 of safety and perpetuation. The power of rapid increase, the 

 habit of making subterranean abodes, or of seeking food only at 

 night, the poisonous sting, the powerful jaws, minuteness of 

 size, or the being armed with spiny processes, are all advantages 

 to their possessors'; and the first rudimentary appearance of any 

 of these, in however slight a degree, would inevitably lead to 

 their persistence and perpetuation, and to the further develop- 

 ment of such peculiarities by the preservation of all favourable 

 and the destruction of all unfavourable variations. 



The new genus, Echinopla, consists of a few species somewhat 

 resembling Polyrliachis, but wanting the spines, and generally 

 covered with deep strise or bristles. They are very scarce, being 

 almost all found solitary on leaves in the damp and gloomy 

 forest ; and I never observed their nests or obtained any other 

 clue to their habits. They are very sluggish as compared with 

 the activity of most ants. 



