On the Hessian Fly. 147 



ber are found together. Sometimes twenty or thirty are 

 found in the same sheath, the upper ones frequently die 

 for want of sap, and very few thus situated arrived to 

 their proper size. 



They continue growing in the caterpillar state between 

 four and five weeks^ towards the latter part of which 

 time they change from a light colour to somewhat of a 

 brownish cast, and then to a dark brown, the outward 

 coat of the caterpillar becoming a hard shell or covering 

 for the chrysalis, which change takes place the latter 

 end of May or beginning of June. 



3d. The chrysalis state. In this state they receive no 

 nourishment, and continue without any apparent outward 

 alteration about four or five weeks ; and in this time the 

 last transformation takes place, and the insect appears in 

 its most perfect state of a fly, which perforates the case 

 of the chrysalis, and makes its appearance in the latter 

 end of July or beginning of August. 



4th. The fly is small, has long slender legs, wings long 

 and single, and when they join to the body or thorax, 

 taper almost to a point ; towards the other extremity they 

 expand, and at the end form nearly a semicircle ; the 

 head and thorax are very small in comparison with the 

 abdomen, which is large, particularly in the females ; 

 and when viewed with a microscope, there appear round 

 the abdomen" many beautiful circles of a pale red, in- 

 clining a little to a yellow colour. 



In the last state the insect is very active, moving from 

 place to place with great agility ; and in the latter part of 

 August and beginning of September their principal mi- 

 grations take place : those vegetables on which they 

 deposit their eggs being scarce, they emigrate in search 

 of greater plenty. 



They now copulate, and soon after begin to deposit 

 their eggs ; and as nearly as I could discover, this pro 



