180 American Horticnltuy<d Sodefi/. 



forms, and when ;i t^ufficient quantity of food has been thus provided to fur- 

 nish a supply for a wasp during the period of its larval existence, a single 

 •egg is deposited, and the cell closed, ujiually with tempered clay or earth. 

 Here the egg soon hatches, and the young larva begins to feed on the insect 

 stores provided by its thoughtful parent, and by the time the contents of the 

 <;ell are consumed the solitary grub has reached the end of its larval life, 

 when it changes to a chrysalis within the cell, from which there soon escapes 

 a mature wasp. One species is known to pack its cells chiefly with canker 

 worms, and many others use injurious insects for this purpose. While 

 multitudes of insects are consumed by these Avasps, we are under far greater 

 obligations to the ichneumon flies, which also belong to this order, Hymenop- 

 tera, for the friendly offices they perform. 



These insects belong to the second, or parasitic class. They deposit their 

 •eggs either under or on the skin of the caterpillar they attack. In this class 

 may be found insects of all sizes, from the tiny Pkromalus puparum, which 

 preys on the cabbage worm, and is so small that it requires a keen sight to 

 follow it in its movements, up to that large and powerful species, the long- 

 tailed ophion, Ophion macrurum, which parasites and destroys the caterpil- 

 lars of our very largest moths. Some time ago I had the opportunity of 

 watching a female of the little parasite of the cabbage worm, while engaged 

 in the work of depositing her eggs. She settled herself quietly down on the 

 back of a caterpillar, towards the hinder end of its body, with her head to- 

 wards the caterpillar's head, and paused awhile ; then, with a sudden move- 

 ment of her ovipositor, so quick that the motion almost escaped detection, 

 she thrust an egg under the skin of her victim. The caterpillar seemed 

 startled; its body quivered ; and it jerked its head suddenly about as if it 

 wondered what was the matter. The larva soon (juieted, and the little tor- 

 mentor sat perfectly composed on the spot where she first settled. Presently 

 another thrust was made, followed again by uneasy movements of the cater- 

 pillar; and in this marnier. in the course of a very few minutes, quite a num- 

 ber of eggs were deposited. The eggs so placed soon hatch into little grubs, 

 which feed upon the fatty portions of the body of their victim, avoiding the 

 vitals, and so injure it that it dies soon after it has entered the chrysalis state. 

 The parasites complete their changes within the chrysalis of the butterfly, 

 and escape through small holes made in the chrysalis. Some of the laiger 

 species deposit only one or two eggs in a single caterpillar: and as on ac- 

 count of the size of these insects they can not avoid being seen by the cat- 

 erpillar, their movements arc dexterously and quickly made. The ichneumon 

 flies are among the most active of the insect hosts; they fly rapidly, and 

 when alighted, run with considerable speed over the upper and under sur- 

 faces of the leaves of the plant, shrub, or tree, on which they settle, piercing 

 eagerly with keen sight into every nook and corner in search of caterpillars. 

 The habits of all the species in this group are very similar. 



Another group of useful insects is found among the Diptera or two-winged 

 flies, and arc known as tachina flies. These deposit their eggs on the skin 



