Page:Popular Science Monthly Volume 54.djvu/86

From Wikisource
Jump to: navigation, search
This page has been proofread, but needs to be validated.
78THE POPULAR SCIENCE MONTHLY.

have become gorged with food; this can be observed in the drawings.

The cow of the yellow ant should not be confounded with her harmful cousin, Phylloxera vastatrix, the deadliest enemy of the grape. Fortunately for us, this last-mentioned aphis does not abound in the United States; in France and other European countries, however, phylloxera has occasioned the loss of millions of dollars.

PSM V54 D086 Cocoon larva eggs and adult aphis lion.png
Cocoon, Larva, Eggs, and Adult of Aphis-Lion (Chrynopha). Slightly modified from Comstock.

Notwithstanding the fact that the ants are exceedingly zealous in guarding their property, many of the aphides fall victims to the assaults of their enemies. The most cunning, insidious, and crafty of their foes are the ichneumon flies, three varieties of which are continually, during the summer months and m autumn, endeavoring to cradle their young in the bodies of the aphides.

One of these flies, which can be seen in the drawing, is quite large; I am inclined to believe, therefore, that their larvae do not pupate in the bodies of their hosts, but undergo further metamorphoses elsewhere. Another of these flies is very small, hardly larger, in fact, than the insect which it selects as a living cradle for its young. The ichneumon shows rare intelligence, inasmuch as she invariably deposits her eggs on the young members — the calves, as it were — of the herd; she seems to know that the older aphides would die before the ichneumon grubs arrived at a suitable age for pupation; hence she selects the young ones. She runs here and there about the colony until she finds a young aphis; then, curving her abdomen between her legs, she will quickly lay an egg on the body of the unconscious insect. When the egg hatches the larva feeds on the body of its host (carefully avoiding the vital organs, however) until the time arrives for it to undergo further metamorphoses. The animated cradle and cupboard eventually dies, but not until its queer baby has arrived at an age at which it has no further use for it.

The ants are fully aware of the fact that the ichneumon is a deadly enemy of their cows; hence, when one of these flies is seen hovering over the herd, they at once become alert and endeavor to chase her away whenever she alights. She manages, however, to