PARASITISM 



133 



The Ophions present a different type although they are readily 

 recognized as belonging to this group. The ovipositor, however, is not 

 so conspicuous, and the abdomen, though somewhat club-shaped, is 

 strangely flattened so that from above it looks like the edge of a knife 

 blade, while from the side it is quite wide. Members of this group 

 attack especially the larvae of our large silk- worm moths and some 

 of our butterflies. This is a very interesting group but not of great 

 importance since they do not work to a great extent at least upon any 

 of our injurious insect pests. 



A second group of the four-winged parasitic insects is the Bra- 

 condiae. This is a large group of very small insects which cannot be 

 described without a characterization which would be too technical for the 

 purposes of this paper. The work, however, may be readily recognized 

 since they act like none of the other parasites. Their method of pupation 

 may be of two kinds, namely, external pupation where the larvae come 

 outside of the caterpillar before entering the resting stage, and internal 

 pupation where the larvae remain within the caterpillar in order to 

 complete their development. Those which follow the first named method, 

 that of external pupation, feed upon the fatty tissues of the host much 

 the same as do other parasites. When parasites are full grown they 

 worm their way through the skin on the back of the caterpillar until 

 they are entirely outside except just enought of the tail to hold them 

 stacking out perpendicular to the body of the host. Each of the larvae 

 bends its head over and secures itself with a sticky fluid at the place of 

 attachment then proceeeds to spin a cocoon about itself. Infested 

 caterpillars such as our "tomato-worm", "grape-wine worm," and others 

 may often be seen with two or three hundred of these smooth white 

 cocoons about half the diameter of a pencil lead and one-eighth of an 

 inch long standing on end and pointing in all directions. When the 



Larva of Tomato-worm with cocoons of braconid, 

 Apanteles congregatus attached. [After Weed.] 



