74 ANIMAL ACTIVITIES. 
needed by the aphis, is relished by other insects, 
notably the ants, which may be seen stroking the pro- 
jections from which the honey-dew exudes and eagerly 
eating the sweet fluid. 
So much do the ants appreciate this honey-dew that 
they take great pains to care for their friends the 
aphides, in many cases herding them as men herd 
cows, and sometimes carrying their attentions so far 
as to take the winter eggs of their cows into their own 
houses to keep them from frost and enemies. With 
returning spring these eggs are taken out again and 
placed upon their proper food-plants to hatch in the 
warmth of the sun and produce another colony of 
aphides. 
The Ichneumon-fly. Teachers of Zodlogy fre- 
quently have brought to them for identification and 
explanation a caterpillar, having his back covered with 
a mass of silken cocoons. If we wait for the cocoons 
to hatch we may see coming from each a black four- 
winged insect from one eighth to one fourth of an inch 
in length. The female of this insect, when mature, 
deposits great numbers of small eggs directly under 
the skin of a living caterpillar. These eggs soon hatch 
into small grubs or maggots which live on the fat of 
their host, not interfering with his digestive apparatus 
or other vital organs. After a time the full-grown 
larve bore holes through the caterpillar’s skin, come 
out of their living prison and spin cocoons, fastening 
each to the caterpillar’s back by a thread of silk. In 
these cocoons the pupa stage is passed and the adult 
insect gnaws his way out to begin another cycle. 
These insects are often called microgaster-flies. They 
belong to the order Hymenoptera (Fig. 67). 
The Sand-wasp. Still another method of preparing 
fresh meat for the young has been invented by some of 
the wasps. These wasps catch a caterpillar, a spider, 
or some other insect, and sting him in such a way 
in the thoracic ganglia that the victim becomes 
