THE CANADIAN ENTOMOLOGIST. 109- 



and then sharpen to a point the tube thus formed, to be inserted in the 

 •caterpillar ; a tube is also inserted in the other end (see fig. 21.) For 

 myself I prefer the simple straw. 



Ihc operation. Kill the subject by a drop of ether or by a plunge in 

 spirits ; if it be a hairy caterpillar, it should remain at least half an hour 

 in alcohol, and then rest on bibulous paper for forty-eight hours; other- 

 wise the hairs drop off in the subsequent operation. Then placing the 

 caterpillar in the left hand, so as to expose its hinder extremity beyond 

 the gently closed thumb and first two fingers, enlarge the vent slightly at 

 the lower edge by a vertical cut with the scissors ; next lay the larva 

 either upon bibulous paper on the table, or upon soft cotton cloth held in 

 the left hand, and press the extremity of the body with one finger, always 

 with the interposition of cloth or paper, so as to force out any of the 

 contents of the rectum ; this process is continued from points successively 

 farther back, a slight additional portion of the contents of the body 

 being gently pressed out with each new movement. Throughout all this 

 process great care should be taken lest the skin should be abraded by too 

 violent pressure, and lest any of the contents of the body soil its exterior 

 or become entangled in the hairs or spines : to avoid the latter, the 

 caterpillar should be frequently removed to a clean part of the cloth or 

 paper. When a portion of the intestinal tube itself becomes extruded, it 

 should be seized with a pair of strong forceps, and, the head remaining in 

 the secure hold of the left hand, the tube should be forcibly but steadily 

 torn from its attachments ; with this most of the contents of the body 

 Avill be withdrawn, and a delicate pressure passing from the head toward 

 the tail will reduce the subject to a mere pellicle. 



The alcohol lamp is now lighted and placed in position beneath the 

 oven ; a straw is selected, of the proper size to enter the enlarged vent, 

 .and the tip, after being cut diagonally with sharp scissors, is moistened a 

 little in the mouth (to prevent too great adhesion of the skin to the 

 straw) and carefully introduced into the opening of the caterpillar ; the 

 process may be aided by blowing gently through the straw. When the 

 skin is slipped upon all sides of the straw to the distance of nearly a 

 quarter of an inch, without any folding of the skin and so that both the 

 iinal prolegs protrude, a delicate pin (Edelston and Williams, No. 19, is 

 best) is passed through the anal plate and the straw. 



By this time the oven will be sufficiently heated to commence the 

 drying process, which consists simply in keeping the caterpillar in the 



