158 HYMENOPTERA CHAP. 



Insect is subterranean in its habits, and is said to change its 

 abode very frequently. T. erraticum occurs somewhat rarely in 

 Britain. Forel has also noted the habits of Lioinetopum mic.ro- 

 cephalum, another small European species of Dolichoderides. It 

 is a tree-ant, and by preference adopts, and adapts for its use, the 

 burrows made by wood-boring beetles. It forms extremely populous 

 colonies which may extend over several large trees, the inhabitants 

 keeping up intercommunication by means of numerous workers. 

 No less than twelve mighty oaks were found to be thus united 

 into a colony of this ant in one of the Bulgarian forests. The 

 species is very warlike, and compensates for the extreme minute- 

 ness of its individuals by the skilful and rapid rushes made by 

 combined numbers on their ant-foes of larger size. 



Fritz M tiller has given a brief account, under the name of 

 the Imbauba ant, of a Brazilian arboreal ant, that forms small 

 nests in the interior of plants. The species referred to is no 

 doubt an Azteca, and either A. instabilis, or A. mulleri. The nests 

 are founded by fertilised females which may frequently be found 

 in the cells on young Cecropia plants. Each internode, he says, 

 has on the outside, near its upper part, a small pit where the wall 

 is much thinner, and in this the female makes a hole by which 

 she enters. Soon afterwards the hole is completely closed by a 

 luxuriant excrescence from its margins, and it remains thus closed 

 until about a dozen workers have developed from the eggs of 

 the female, when the hole is opened anew from within by the 

 workers. It is said that many of the larvae of these ants are 

 devoured by the grubs of a parasite of the family Chalcididae. 

 This Insect is thought to protect the plant from the attacks of 

 leaf-cutting ants of the genus Atta. 



We may here briefly remark that much has been written 

 about the benefits conferred on plants by the protection given to 

 them in various ways by ants : but there is reason to suppose 

 that a critical view of the subject will not support the idea of 

 the association being of supreme importance to the trees. 1 



Sub-Fam. 2. Myrmicides. Pedicel of abdomen formed of two 

 well-marked nodes (knot-like segments). Sting present (absent 

 in the Cryptocerini and Attini}. (It should be noted that the 



1 See von Ihering, Berlin, ent. Zeitschr. xxxix. 1894, p. 364 ; and Forel, Ann. 

 Soc, ent. Bclyique, xl. 1896, p. 170. 



