394 



AN ECONOMIC ENTOMOLOGY. 



part in the economy of certain species of ants. As we learnt in 

 the chapter on plant-Hce, these insects are furnished with a pair 

 of honey-tubes near the end of the abdomen, through which there 

 is excreted a sweet, almost transparent, liquid, of which the 

 ants are very fond. In many cases aphids live on the roots of 

 plants during the whole or a part of their life, and such species 

 are in nearly every instance carefully tended by ants. We may 

 find, on lifting up a large stone at the foot of a tree near the 

 edge of a wood, that all the little rootlets covered by it are clus- 

 tered as thickly as possible with plant-lice, and that around them 

 the earth has been carefully tunnelled out ; in other words, we 

 have the roots forming part of the nest system of an ant colony. 

 As the plant-lice increase in number, additional roots are laid 

 bare, and the young are transported to them that they may 

 always find an abundance of food. In return, the ants, whenever 

 the desire seizes them, call upon one or more of the aphids, and, 

 by touching them with their antennae, induce them to give up 

 a drop or two of their sweet secretion. Exactly how large a 

 proportion of the food of the ant colony this kind of material 

 forms is yet undetermined ; but certain it is that plant-lice con- 

 stitute a very important element in the supply of some species, 

 and fully represent our cattle for all ant purposes. 



Little brown ants about three-sixteenths of an inch in length 

 occur very abundantly in the fields throughout almost all parts 

 of our country, building small underground nests. These ants 

 belong usually to the genus Lasiiis, and may be found, especially 

 early in the year, on the leaves of all sorts of plants infested by 

 aphids. In melon and sweet potato fields they are often ex- 

 tremely abundant, and it is more than likely that they are active 

 in transporting from one plant to another the lice infesting these 

 particular crops. Of the Lasiiis brimneus, we know that it tends 

 the corn-root louse, gathering the young larvae in the fall and 

 preserving them during the winter safe beyond the reach of any 

 natural enemies, colonizing them in spring upon the roots of corn 

 plants. Indirectly, therefore, these ants are decidedly injurious 

 through their relation to the plant-lice. Other species gather 

 plant-lice eggs and care for them during the winter, colonizing 

 the young upon proper food plants in spring. 



We find certain other species making their hills in our lawns 



