On the Hessian Fly, 145 



in August and the beginning of September. The first 

 year they appear in no great numbers, and scattering ; 

 but the next year they advance in great numbers, and, 

 with the increase of those that came the preceding year, 

 make great destruction. It was in the second year of 

 their appearance in my neighbourhood, that I began to 

 be particular in observing them, and from notes taken 

 that and succeeding years, I draw this account. 



As this, like most species of flies, undergoes several 

 transformations before they arrive to a perfect state, I now- 

 state such observations as I have made upon them in 

 their different stages, until they arrive to the fly. — First, 

 of the egg, then of the larva or caterpillar, then the aurelia 

 or chrysalis, and lastly, when they arrive to the mature 

 state of a fly. 



1st. The eggs. These are deposited by the parent 

 fly on the leaf or blade of the wheat, at different times 

 in the spring. The latter end of April and beginning of 

 May, they may be seen laying their eggs on the leaves 

 that have grown that season ; they deposit them in the 

 small creases that are longitudinal in the leaf. The egg 

 is scarce discernible with the naked eye, but with a mi- 

 croscope it appears oblong, both ends of the same size, 

 and of a beautiful glossy pale red, a little inclining to 

 yellow. After a few days more, or fewer, as they are 

 warmer or colder, the egg hatches, and the young cater- 

 pillar appears. 



2d. The larva or caterpillar. It is in this state that 

 the insect does all its mischief: when the caterpillar first 

 appears out of the Qgg, it retains the pale red colour of 

 the egg, is wrinkled, and has a considerable degree of 

 agility. As soon as hatched it creeps down the leaf until 

 it comes to where it joins the head or main stalk of the 

 plant ; if the stalk has advanced much, so that the pedicle 

 of the leaf forms a sheath round the stalk, it enters the 



