BEES, WASPS, ANTS, ETC. 521 



existing between them and other insects, and in some cases between different 

 species of ants. Very many species of insects live in ants' nests, the greater majority 

 of which are beetles. Thus Andre gives a list of 587 species of insects which 

 are habitually found in association with ants, of which number 542 are beetles. In 

 the case of l^eetles, it is not clear just what is the relation existing between them 

 and the ants ; but, in case of certain other insects, the connection is easily seen. The 

 most familiar example is the association of various species of plant-lice and bark- 

 lice (Aphididse and CoocidsB) with ants. In the summer time it is an easy matter 

 to find lines of ants ascending and descending trees or other plants. If the ascend- 

 ing ants be watched, they will be found to go to colonies of plant-lice or bark-lice 

 which are feeding upon the tree. From these insects the ants obtain a sweet 

 secretion upon which they feed. The giving out of the sweet matter, or honey-dew 

 as it is termed, can be easily seen in case of the plant lice. There is in many species 

 a pair of tubes on the dorsal aspect of the abdomen, from which the honey-dew 

 exudes. If a colony of plant lice which are attended by ants be watched for a few 

 minutes, one will usually see ants soliciting the honey-dew by patting the aphids with 

 their antennae, and the aphids will also be seen to respond by emitting from the lioney 

 tubes one or more drops of the bright, transparent liquid. In return for this honey- 

 dew the ants exercise a protecting care over the plant lice, driving away predaceous 

 insects which would destroy them, and caring for them in many other ways. Fre- 

 quently ants keep theii- herds of plant lice in their nest. This is especially true of 

 the common yellow ants which build their nests under stones, where the roots of plants 

 can penetrate; from which the jilant lice draw their nourishment. Thus the ants' 

 nest serves also as a pasture for the herds of the ants. Other ants travel long 

 distances to attend plant lice which are feeding upon hei'bs or trees remote from their 

 nest. The long tunnel described in a previous paragraph was simply a road leading 

 from the nest of the ants to a tree upon which their plant lice were feeding ; and, as 

 this was a tall forest tree, the ants, after reaching it, had to climb to a great height. 

 Ants cany the plant lice about from one place to another, taking them from an old 

 pasture to a new one. Sometimes they build a shed of mud over a colony of plant 

 lice which are feeding on a plant in the open air ; but perhaps the most wonderful 

 thing in connection with the lelations of ants and ajihids is the fact, now well estab- 

 lished, that not only do the ants care for the plant lice, but they also care for the eggs 

 of the plant lice. And not merely for the eggs of those species which live in the nest 

 of the ants, but also for species which feed on the leaves of plants in the open air. 

 " The eggs are laid early in October on the food plant of the insect. They are of no 

 direct use to the ants, yet they are not left where they are laid, exposed to the sever- 

 ity of the weather and to innumerable dangers, but brought into the nests by the ants, 

 and tended by them with the utmost care, through the long winter months, until the 

 following March, when the young ones are brought out and again placed on the young 

 shoots of the daisy." 



The plant lice (Aphididse) are the most common and abundant of the different insects 

 which excrete honey dew and are attended by ants. Next in abundance are the bark 

 lice (Coccidae). In this family only those species which are not furnished with a scale 

 (Lecaninse and Coccinse) are thus attended. Certain other homopterous insects bear 

 the same relation to ants. I have often seen the two-spotted leaf-hopper, Enchenopa 

 Unotata, emit from the caudal end of its body a drop of clear fluid, which was eagerly 

 eaten by attending ants, and which I believe to be honey-dew. The caterpillars of 



