18 THE CANADIAN ENTOMOLOGIST. 



she had spent so much labor upon, and which now serves to protect the 

 cocoon, until, a few days later, a pretty, gauze-winged tly, not much over 

 . I inch long, comes forth, ready to begin its career of destructiveness. 



This is one of Nature's ways of keeping down butterfly caterpillars. 

 But the parasites that aid in this work are themselves kept in check by a 

 similar process. On one occasion 1 found quite a number of minute flies 

 issuing from one of the Atalaiita parasite cocoons. They would have 

 been unnoticed but that the cocoon was lying in a closed glass tube. A 

 hole was discovered, as if made by a pin, and through this the flies had 

 come. In this case the secondary parasite must have found its way into 

 the apparently tight case of the caterpillar, and stung the grub of the 

 Apatclcs just as the latter broke its way out, and while it was yet 

 naked.* I found also a minute red spider inside one of the cases with a 

 grub of the fly, and spiders do their part in keeping down parasites. 



But to return to our larvae. One in 3rd stage ; that is, after 2nd moult, 

 verv soon closed the large leaf it had been placed on, flrst biting the mid- 

 rib, i'his habit of severing the rib obtains quite to the last stage, as is 

 evident from inspection of the deserted cases met with in my searches. 

 Another in same (or 3rd) stage rested for two days under the bit of leaf it 

 was attached to when I pinned it to the plant, making no attempt at a 

 case, but went outside the bit of leaf to feed. The third day it mo\ ed up 

 the stem and took possession of a leaf of the second pair, but instead of 

 bringing the edges fully together in the usual way, did so l)ut partially, 

 and twisted the end of the leaf up and over till the case was completely 

 closed. 



.\ larva in 4th stage, /. e., after 3rd moult, began at once to draw the 

 edges together, not having bitten the mid-rib. 'i'he case was closed at 1 1 

 a. m. By 3 p. m., same day, this larva had constructed a new case, quite 

 capacious and made of three leaves. Before deserting the lirst one, it had 

 eaten fully half, from the outer end. Next day, it had bitten off the main 

 stem of the plant, just above its case, and had eaten the top leaves. This 

 larva Anally, after its 4th moult, left the ])lant and pupated in the top of 

 the guaze bag, which covered the plant and flower-pot. 



I brought in another larva, which had just passed its 3rd moult. After 

 moving about and examining several leaves, at 30 minutes from arrival, it 

 had established itself between two of .the second and third pair, which 



* Mr. Howard, of the Agricultural Uept., Washington, informs me that this little 

 fly is of the genus Tetrasticluis, the species probnbly undescribed. 



