ENTOMOLOGICAL SOCIETY OF ONTARIO. 



55 



Oregarina^ meet they adhere one to the other, and then surround themselves with a 

 cyst. The partition between them disappears ; the nuclei also disappear and then the 

 •case becomes filled with spindle-shaped bodies called " pseudonavicellai,'' which in due 

 time escape from the cyst into the surrounding medium. Their after history is not 

 yet told. 



It is said that when a gregarina finds itself left in a state of single blessedness it 

 does not give itself over to despair, but proceeds to encyst itself, and to produce pseudo- 

 navicelhe on its own account. 



The internal insect-parasites of insects are of two kinds : (1) Those that complete 

 their metamorphoses within their victims ; and (2) Those that leave their hosts on the 

 completion of the larval stage. 



Of the former, RJiogus intermedius, Cress, affords us an example. It assails the larvis 

 of Apatela liastulifera Abbot and Smith, which feeds upon the alder Aldus incana^ 

 "VVilldenow. 



The parasitized Apatela larva may be found in the autumn attached to the leaves 

 and stems of the plant. In them the ichneumon grubs, having attained their growth, 

 form their thin, brown, closely-woven cocoons, which are arranged at an angle of about 

 forty-five degrees, and usually in four rows. I have drawn out with a setting-needle 

 no less than thirty -five pupa? from one caterpillar. They were all placed with the head 

 upward. Very regular rows of round holes show how the adult ichneumons escape from 

 their nurseries. As I have found the flies at large in the middle of October I presume 

 that some of them, at any rate, pass the winter in the perfect state. 



There are much larger insects that undergo all their changes within their hosts such 

 as Ophion miorurion, Linn, F(g 38, in the Saturniad<i3; Opheletes glaucopterus, Linn, in 

 Oimbex. The eggs of these are laid singly or in pairs. 



Fig. 39. 



Fig. 38. 



Of parasites that leave their hosts when full fed and before undergoing the pupal 

 change Apanteles longicornus, Prov, is an example. The fluflfy, yellow masses of the 

 oocoons of this species may often be seen attached to the remains of noctuid larvse, under 

 the rails of fences, etc. 



What entomological neophyte has not experienced the disappointment of finding, on 

 a sudden, a carefully tended Sphinx caterpillar in a state of collapse, and bristling with 

 the larvaj of some microgaster, that have extruded themselves from it, and that proceed 

 to spin their cocoons about its remains. 



But surely the most economical of all the internal insect parasites is the well-known 

 Cryptus extrematus, Cress. The larvae of this insect find themselves, they know not how, 

 in the inside of a caterpillar of Platijsamia Cecropia, Linn, and forthwith commence the 

 herculean task of reversing the state of things in which they find themselves, and of 

 environing their environment — putting the outside grub into their insides — baginning 

 with the fatty portions of it. Numbers and perseverance accomplish the task, bat not 



