A. S. Packard. Jr. on certain Entomological Speculations. 213 



one, of a much thinner and more delicate texture, becomes the true 

 skin of the matured pupa," p. 577. 



Second. Hear Dr. A. Fitch* in regard to the semi-pupa state of 

 Cecidomyia, who has been the first, as far as we are aware, up to the 

 date of this article, to observe aud plainly designate this state in the 

 Diptera. terming it the embryo-pupa. 



"Thus, from these observations we obtain a pretty full and distinct view of 

 the processes whereby the insects of this genus Cecidomyia become changed 

 from larvae to pupfe, by this transformation losing the mouth and jaws of the 

 worm and acquiring the rudimentary wings and legs of the fly. As the first step 

 of this change, at the anterior end of the larva the cutis or opake inner skin be- 

 'comes wholly broken up and dissolved into a watery fluid, whereby the thin 

 transparent outer skin or cuticle is elevated like a vesicle or blister, which occu- 

 pies about a fourth of the length of the worm on its under side, but is much 

 shorter on its hack. The insect is now in its embryo-pupa state, having lost its 

 larva form and having not yet assumed its pupa form. In the fluid contained in 

 this vesicle the wings, le^s and antennae of the future fly now begin to be de- 

 veloped whereby the sheaths of the wings at length come to be discerned im- 

 mediately under the skin. This skin is exceedingly thin, delicate and 

 transparent, like the tunica arachnoides of the human brain, a mere film as thin 

 as a spider's web. Eventually, the insect by gently writhing ruptures this film 

 at its anterior end and gradually crowds it off downward to the lower end of the 

 vesicle, carrying the minute black jaws of the larva with it. It there remains, 

 becoming dry and torn into shreds which flake and fall off by the continued 

 motions of the insect. At the same time, from the remainder of the surface 

 not occupied by this vesicle, a still more slight and delicate film, appearing 

 as though the worm had been wet in milk which dried upon it, forming an ex- 

 ceedingly thin pellicle or scurf, becomes separated by the same motions of the 

 insect and drops off in minute scales scarcely to be perceived with a magnify- 

 ing glass. And now the insect has accptired its perfect pupa form, the moulting 

 which occurs in this change being, not a throwing off of an entire skin like 

 that which the larva often parts with when it is done feeding, and that which 

 the pupa always leaves when it changes to a fly, but only a slight scurf-like 

 exfoliation from the surface — so slight that in a small delicate species like the 

 wheat midge it is doubtful whether any indications of it can be perceived, 

 p. 807." 



Newport also briefly describes a similar process in the same period 

 of life, in the Hymenoptera and Lepidoptera, as regai-ds the changes 

 of the body-walls of the insect, with a detailed and richly illustrated 

 account of the nervous system, in the Philosophical Transactions, 

 London, 1832— 36. 



This semi-pupa stage is. then, precisely similar to that which we 

 have observed in Bombus,* in alcoholic specimens, but which Dr. 

 Fitch, by an ingenious device whereby he caused the Cecidomyia to 



* Sixth Report on the Xoxious and other insects of the State of New York, by 

 A-a Filch. M. D. Transactions of the New York State Agricultural Society, 

 18(50. Albany, 1801, p. 806 and SU'J. 



