TRANSACTIONS OF THE SECTIONS. 123 



If a leaf eateu by this larva be held to the light no symptoms of its operations 

 ■will be apparent ; but if, instead of holding the leaf between us and the light, we 

 look down on it slautways, we shall perceive some slightly iridescent tracks, which 

 have very much the appearance as though a snail had been crawling across the leaf. 



Another peculiarity of this larva is that it never moults ; its skin is apparently 

 of so elastic a nature, that it grows with the larva; most larvae cast their snins four 

 or five times in the course of their lives, but this larva never once undergoes that 

 operation. Besides this, it never sleeps; most larvae, after enj oying a hearty meal, 

 may be found inactive and inert, in a position which conveys to us precisely the 

 idea of sleep, but a Phyllocnistk larva never sleeps, it is iilways eating ; from its 

 exclusion from the egg to its being full-fed, night or day, its jaws are perpetually 

 at work. This is not true only of the larva of Phijllocnistis, it occurs throughout 

 the extensive genus of Nepticula. I have had abundant opportunities of observing 

 these larvae at all hours of the day and night, and, unless they are ill or dying, 

 they are invariably eating. Their jaws have certainly solved the problem of per- 

 petual motion. 



Ehrenberg expressed surprise that the Infusoria never sleep ; and Owen, after 

 long watching the motions of the Polygastrica, concluded they were generally of 

 the nature of respiratory acts, and not attempts to obtain food or avoid danger. He 

 adds, " Very seldom can they be construed as voluntary, but seem rather to be 

 automatic ; governed by the influence of stimuli, within or without the body, not 

 felt but reflected upon the contractile fibre ; and therefore are motions which 

 never tire." 



But the motions of these small larvae are certainly not automatic ; you frequently 

 see the larva turning its head about from side to side of its mine, as though con- 

 sidering where it should eat a bit next, and immediately it has determined that 

 point it sets to work with a tcill, little indicative of involuntary action. 



On the Effect of Temperature and Periodicity on the Development of 

 certain Lepidoptera. By Dr. Verloren, of Utrecht. 



A Table was exhibited showing the period at which the pupae of the Sphinx 

 Lic/ustri were hatched. From these tables it appeared that the great proportion of 

 the insects was produced in the middle of June, indepeudent of the state of the 

 temperature of the season ; and it appeared that in cases where the development of 

 the insects had been retarded beyond the fixed period in one year, they appeared 

 only during the limited period in the succeeding year. The observations had been 

 extended through a number of years, and had enabled Dr. Verloren to establish 

 several other interesting physiological facts connected with the species in question. 



Mr. Westwood gave an accoimt of an insect which, on account of its anomalous 

 character, had been referred to three different orders of the class Insecta, and which 

 forms the genus Aeentropus of Curtis, the type being the Phryganea nivca of Oliver, 

 regarded as Trichopterous by Curtis, and as Neuropterous by Stephens : Mr. West- 

 wood had many years ago endeavoured to prove it to be Lepidopterous from a con- 

 sideration of the structure of the perfect insect alone. The transformations of the 

 species having, however, been recently observed by Mr. Brown of Burton-upon-Trent, 

 the opinion of Mr. Westwood had been fully borne out, as was shown by a series of 

 highly magnified diagrams representing the details of the insect and its metamor- 

 phoses, contrasted with those of the orders Trichoptera, Lepidoptera, and N euro- 

 ptera. The genus appears to be most nearly allied to the family Crambiae. 



On Mummy Beetles. By J. O. Westwood, M.A., F.L.S. 



The object of this paper was to show that no change had taken place in the struc- 

 ture and habits of several species of insects during the period which had elapsed 

 since the embalment of the mummies buried in the pyramids of Egypt. A number 

 of species of such insects had been recorded by Latreille in the work upon Egypt 

 by M. Calliand ; and Mr. Westwood exhibited species of the genera Necrobia and 

 Dermestes found within the bodies of mummies by Dr. Pettigrew, and which must 

 have found their way into such bodies during the process of embalment and before 



