144 
Psyche 
[December 
midation there are also attacks upon vegetation. In one case 
catbriars growing to overhang the mound on the north were 
attacked and the ants seen to nibble the bases of the leaves that 
overhung the mound. In. other cases small shoots of poplar 
about a foot in height were attacked, the twig nibbled near the 
base and farther up irregularly and the bases of the leaves bitten 
till the leaves shrivelled. Also rank upgrowing shoots of black- 
berry arising after a wood fire that killed most all vegetation 
down to the ground were seen to be attacked by these ants which 
opened their jaws as wide as possible to bite the bark of the upper 
parts of the bramble and at the bases of the leaves, which wilted 
and drooped down. Some other smaller plants were also at- 
tacked. The attack involves not only biting, but curving of body 
and apparently ejection of acid and resulting brown dead areas 
on the plant. Now these attacks were two to four feet from the 
mounds and on all sides without any discerned reference to the 
shading effects that might be assumed, in fact some of the objects 
attacked could scarcely intercept any appreciable light and one 
might compare the attack to that of an ant upon a new object 
as upon the legs of a person standing near a nest, when the ant 
runs up till something soft enough to be bitten is encountered 
and then bites persistently in one spot. Also in founding a new 
mound the ants did kill all the small plants in and close to the 
mound when its foundation is first begun. 
It may well be that the responses of the ants to sun and 
shade are very complex and deeply ingrained and that the mere 
warming of their bodies may not be the decisive factor in making 
them work more on the sides of the mound exposed more to the 
sunlight. 
As the mound is largely useful as an incubator for the 
young, the slight differences in temperature between various in- 
ternal parts of the mound may be potent, as in sprouting seeds or 
growing bulbs, and be the basis for the ants actions. In one 
mound thermometers showed differences varying from 25.5° to 
32°C. when the natural soil near by was 24°C., June 1926. 
Whether investigation shall prove that the internal tem- 
perature of the mound is a factor or not, the facts seem to be 
that these ants do wdrk more on the sun side and that the 
