214 A. S. Packard, Jr. on certain Entomological Speculations. 



assume this state in the day-time instead of at night, has actually ob- 

 served in life. We have shown that the semi-pupa skin of Bombus 

 comes oif in shreds, like that of Cecidomyia, and especially how slow 

 and gradual is the process. We should also add, that we have ob- 

 served the inception of this state, when the semi-pupa skin is forming 

 beneath the larva skin, in several Ichneumons, in two species of Ten- 

 thredinidae, in a species of a Micro-lepidopterous larva which had been 

 paralyzed by the sting of an Odyuerus, though still alive, and in which 

 these remarkable changes of form could be observed at leisure; and 

 that we have hastily noted, with a view to future more extended 

 study, these changes in the living larvae of Polistes and Vespa, and in 

 alcoholic specimens of Clisiocampa collected for that express purpose. 



From these unpublished observations which confirm those already 

 published and above referred to, we feel quite confident in asserting 

 that the larvae of insects as a general rule, transform gradually by the 

 normal process of growth, i. e. increase by cell-growth or a budding 

 process, and the consequent formation of new tissues, " instead of sud- 

 denly moulting" into the pupa state. 



We would prefer, then, to call semi-pupa what Westwood, Harris and 

 other authors call "larva," i. e. the insect, half larva and half pupa, 

 which lies within the puparium. That the larva exists in its normal 

 condition inside the "flax-seed" envelope, is nowhere stated by Dr. 

 Harris, for the context would not imply it; and this state is by Dr. 

 Fitch, distinctly termed the "embryo-pupa." • "The very mature larva 

 and the true pupa states," then, scarcely appear so "radically distinct" 

 as insisted on by our author; and this "utterly anomalous" " Harris- 

 ian theory" " that the change from the larva to the pupa state is gra- 

 dually and sloicly effected, " will hold its own against the "utterly 

 anomalous theory" set up to oppose it. 



In the same article just cited, Mr. Walsh proposes the "utterly 

 anomalous theory" " that the cocoon of the gall-gnats is exuded, and 

 not spun," adding that "It must, therefore, be either blown like a 

 bubble, or be daubed on the walls of the cell by the body of the 

 insect," — p. 560. 



Now, everybody knows that the silk spun by insects is exuded 

 through the mouth from the silk glands, and that in reaching the air, 

 the secretion, from being gummy, changes to the nature of silk. But 

 very satisfactorily to himself, our author sets aside any such facts, 

 and without first attempting to demonstrate by dissection the existence 



* Proceedings Boston Society Natural History, X, p. 279. We should here 

 -i. iii' that we were unaware of the observations of Dr. Fitch, not having read, 

 until a few days since, either Fitch's remarks or Mr. Walsh's criticism on it. 



