Insects. 470 



discoveries appears so anomalous, so important, so intensely interest- 

 ing, as that just made by Mr. Newport, of the external branchiae of a 

 perfect winged insect. It is well known that many of the same order 

 of insects — the Perlites — possess external branchiae in their prepara- 

 tory stages ; but an obvious reason exists for this, in the fact that in 

 their earlier stages the Perlites are almost entirely aquatic ; and this 

 form of lung, so to speak, is admirably adapted for abstracting from 

 the water the necessary supply of air : but it has been generally sup- 

 posed that the only mode by which animals could inspire or expire 

 atmospheric air, was by its entrance into or propulsion from internal 

 receptacles through apertures in the outer covering of the body. This 

 is not, however, strictly the case ; for although it is common with iso- 

 morphous Neuroptera to spend the period of their preparatory states 

 in the water, exceptions occur, and we find the immature state of a 

 not uncommon Perla, secreting itself by hundreds in the crevices of 

 the bark of pollard willows, when growing in districts abundantly in- 

 tersected by running streams. The creatures appear very inactive by 

 day, and crouch flat on their bellies, but probably at night they sally 

 forth in quest of the insects which the bark of trees seems to attract. 

 Be this as it may, these creatures, although no longer subaqueous — 

 or, supposing they resort to the water by night, of which we have no 

 evidence, at least not constantly subaqueous — yet retain an external 

 apparatus for breathing very similar to that of their subaqueous con- 

 geners. Still we are prepared for this close coincidence between crea- 

 tures of the same genus, and in the same states : but that an instance 

 should have been found in which an entire genus carries this struc- 

 ture with it into its ultimate or imago state, seems to baffle all our re- 

 searches for precedent, and present a feature in insect anatomy for 

 which we are wholly unprepared. Many of our entomological readers 

 will recollect the ingenious hypothesis suggested by Latreille, that 

 the wings of insects were transmuted organs of respiration : the idea 

 that the same organs would serve the double purpose of respiration 

 and locomotion, is due, we believe, to the fact that such was actually 

 the case with the external branchiae of the subaqueous larvae of Per- 

 lites and Ephemerites, the insect using its branchiae as fins to propel 

 it through the water. Mr. Newport's discovery places a direct nega- 

 tive on the hypothesis, since throughout the genus Pteronarcys the 

 wings as well as branchiae are invariably present, the wings occupy- 

 ing the dorsal, the branchiae the ventral surface. He describes the 

 branchiae as follows. 



" They are of the tufted or filamentous form of branchiae. They consist of eight 



