Insects. 481 



which may be traced to the extremity of the filament: but I have not been able to dis- 

 cover any orifice in the extremity of the filament, nor any direct communication what- 

 ever between the external surface and the ramifications of these tracheae, and I doubt 

 much whether any such direct communication exists.'' 



Mr. Newport's specimen was brought by Mr. Barnstone in spirits 

 from Canada, together with many other highly-interesting North- 

 American insects, the whole of which have been presented by that gen- 

 tleman to the cabinet of the British Museum. Mr. Barnstone, who 

 appears much devoted to Natural History, paid great attention to the 

 Perlites in their native localities, and made some highly interesting 

 observations on their economy. He remarked that the so-called pu- 

 pa of Pteronarcys regalis, in the state immediately preceding its at- 

 taining the power of flight, lived constantly in the water at the bottom 

 of streams ; while the corresponding state of Perla abnormis, — the 

 largest species yet known of the genus Perla, — was invariably hid- 

 den in the clefts of water-logged timber, the trunks of trees and other 

 places on the banks, and he has found its exuviae under stones along 

 the banks of rivers ; thus closely corresponding in economy with the 

 English species to which w r e have already alluded. Mr. Newport 

 enquires whether any analogous discrepancy exists in the habits of the 

 perfect insects of the two species. The species of Pteronarcys, as 

 observed by Mr. Branstone, shun the light of day, hiding themselves 

 under stones in damp places, and it is only at nightfall, when the air 

 is charged with moisture, that they appear on the wing. In this re- 

 spect, however, they differ but little from the true Perlae of the old 

 continent. It is a most interesting question, as proposed by Mr. New- 

 port, whether this peculiar structure is a provision of Nature for the 

 damp atmosphere in which the Pteronarcys generally passes its life, 

 or whether the persistent branchiae are accidentally retained, the 

 functions of aeration being performed by other means. Mr. Newport 

 observes : — 



" In regard to the function of aeration being performed by these branchiae in the 

 perfect insect, I may remark that it is of little consequence to the preservation of ani- 

 mal life whether aeration of the fluids of the body be effected directly, by means of air 

 received into the body in lungs, or in spiracles and tracheae, or indirectly, by means of 

 water or vapour, that holds air intermixed with it, through the agency of external 

 branchial organs, in which case the air is brought into contact with the fluids through 

 the surface of these organs in water equally well as in the open atmosphere, when air 

 is taken into the body through the spiracles. The function of branchiae, or aquatic 

 organs, is equally well performed in the open air as in water, so long as the air is 

 charged with a sufficiency of fluid to preserve these organs in a healthy state." 



We trust Mr. Newport will pursue the enquiry he has so ably com- 

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