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VIII. The Anatomy and Development of certain Chalcididse and Ichneumonidse, compared 

 with their special (Economy and Instincts ; with Descriptions of a new Genus and 

 Species of Dee-Parasites. Dy Geokgb Newport, Esq., F.B.S., F.D.S. fyc. 



Read March 20, 1849. 



Preliminary observations. 



A. HE parasitic Hymenoptera include, in their larva state, some of the most imperfectly 

 organized conditions of life to he found in the whole of the Articulata. They leave the 

 ovum delicate, apodal, almost motionless, and entirely incapable of locomotion, and are 

 injured and perish by slight accident, as an abrasion of surface allows the fluids of their 

 bodies to escape quickly and fatally by the wound; and yet these very beings, having 

 passed unhurt through this scarcely other than foetal condition, acquire a perfection of 

 organization, a degree of activity and power, and an acuteness of instinct, fully equal, and 

 perhaps superior to the organic and the functional endowments of other tribes of insects. 

 One section of them, — some of which I shall make the subjects of this paper, — are nourished 

 entirely by suction, and subsist on the fluids of other insects ; and either attached singly 

 to the external surface of the bodies of their victims, or, located internally, between the 

 tissues, they drink up the life-blood prepared for another, without entirely destroying the 

 means of its production. Other species are gregarious and reside in the same cell with 

 their victim ; and while that subsists on vegetable food, — pollen mixed with honey and 

 stored up for it by its parent, — it is attacked on all sides by its insidious enemies, succumbs, 

 and dies as they become nourished. Yet the general form of body, and of the digestive 

 organs, at the earlier periods of growth, is almost precisely the same in most of these de- 

 scriptions of parasite, and the special development of each is regulated by the same laws. 

 They cast their skin at succeeding stages of growth as certainly as do the larvae of Depi- 

 doptera ; but the thrown-off covering is of such extreme tenuity, and is so gradually and 

 almost imperceptibly removed, without interfering with the form or the enlargement of 

 the body, that, hitherto, the deciduation of the tegument of the apodal larvae of Bymeno- 

 ptera has always escaped the observation of naturalists. I have, however, witnessed its 

 repeated occurrence in the genus Paniscus, as I shall show in this paper ; so that these 

 species do not constitute, as was supposed, an exception in this respect to one general law. 

 Much as they resemble each other in external appearance, they do so still more in the 

 structure of their organs of nutrition. The digestive apparatus in the whole of them is at 

 first but a simple, capacious sac or bag, rounded and closed at its larger extremity, with 

 an imperforated intestine proceeding from it, without an anal outlet. It has this form 

 in most of these insects during the earlier periods of the larva state, when the organizing 



