14 



as the last week in August. The past season fully one-half of the 

 Greater Leaf-rollers were destroyed by these parasites. These are 

 the only parasites that I have ever bred from these Leaf-rollers, 

 but it is very probable that other kinds of parasitic insects also in- 

 fest them. 



On the 13th of August I found in a cavity of leaves on a rag- 

 weed a Greater Leaf-roller on whose body were no less than six 

 Tachina eggs. One of these eggs was placed on the cervical shield, 

 one on each of the segments four and seven, two on the under side 

 of segment four, and one on the under side of segment five. The 

 next day there issued from the body of the Leaf-roller a single 

 grub of the parasitic fly described above. This would seem to indi- 

 cate that some kind of Tachina fly also preys upon the Greater 

 Leaf-roller. 



On the 5th of July I found in a rolled leaf in a hazel bush a 

 Greater Leaf-roller which had a Tachina egg attached to the pos- 

 terior edge of the cervical shield. In the same roll was an ellip- 

 soidal, whitish cocoon which measured about three-sixteenths of an 

 inch in length. I placed both the Leaf-roller and the cocoon in one 

 of the breeding cages, but did not succeed in obtaining anything 

 from either of them. 



On the 17th of July I found a cocoon similar to the above in a 

 rolled apple leaf inhabited by a Greater Leaf-roller that was only 

 about one-half grown. Nine days later a small, four- winged fly — 

 the Perilitus limidiatiLS of Cresson — issued from this cocoon. 



The wings of this fly are transparent, and expand a trifle over 

 one-fourth of an inch. The head is yellowish-brown, and the eyes 

 and a small spot on top of the head are black; on this spot are 

 three small tubercles {ocelli). The anterior one-half of the thorax is 

 yellowish ; the remaining portion is blackish. The abdomen is black, 

 with a broad, transverse, yellowish-brown stripe across the middle. 

 The legs and underside of the body are pale yellowish-brown, 

 slightly tinged in places with black. The antennsb are light yellow, 

 and are Clouded and ringed with black. 



Whether the fly lives in its larval state within the body of the Greater 

 Leaf-roller or not I am not prepared to say. Dr. LeBaron has 

 reared a closely allied species — the Perilitus indigator of Eiley — from 

 the Walnut Leaf-crumpler {Acrobasis juglandis, LeBaron),* and from 

 the situation in which the cocoon of the dimidiatus was found it 

 renders it pretty certain that this is a true parasite of the GreateV 

 Leaf-roller. 



The late B. D. Walsh, formerly State Entomologist of llhnois, 

 compares the working of these parasites upon the Caterpillars to a 

 great many springs, all of which exert a certain amount of pressure 

 upon each other; remove one of the springs, and one or more of 

 the others will suddenly spring upward. So if the parasites of any 

 noxious insect are destroyed, this insect will suddenly appear in 

 large numbers where formerly it was almost unknown. It becomes 

 our duty then to ascertain what it is that destroys these parasites 

 and if possible to circumvent it in its work. 



*See the "Fourth Annual Report on the Noxious, Beneficial and other Insects of the 

 State of Missouri;" page 43. 



