ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 305 



a. Insecta. 



Influence of Environment on Caterpillars.*— A. Pictct has made 

 many experiments showing that changes in the environment (diet and 

 humidity) of caterpillars may result in changes in the adults. An 

 aberrant form of Abraxas grossidariata, known in nature, was evoked 

 after two generations of dieting on Euonymits ; the variety urticoides 

 of Vanessa urticce, was obtained by feeding the caterpillars on the flowers 

 instead of on the leaves of the nettle. The influence of humidity on 

 coloration seems very marked, especially during the transition period 

 between larval and pupal life. 



Influence of Humidity on Caterpillars. f — Arnold Pictet finds that 

 humidity has a marked influence on coloration. When the caterpillars 

 of Vanessa urticce and Pohjchloros are fed for ten days with moist leaves, 

 the resulting butterflies have characteristic black markings on the wings. 

 The same kind of result is obtained when the caterpillars are kept in an 

 atmosphere saturated with moisture : then the nervures in V. urticce, are 

 strongly marked in black and the margin of the blue spots is densely 

 black and has invaded the normal area of these spots, which are, there- 

 fore, very small, though extraordinarily brilliant. In short, humidity 

 is a factor in inducing partial melanism, and modifications in this direc- 

 tion are common in nature after rainy periods. It should be noted that 

 when the larvas of V. urticce, are exposed to humid conditions during the 

 transition moult between the caterpillar and pupa state, there result 

 light coloured butterflies with a broad yellow band, crossing the anterior 

 wing and continued in a triangle on to the posterior wing. 



Metamorphosis of Insects.! — Jules Anglas points out the close 

 relations that obtain between the development of the trachea} and the 

 phenomena of metamorphosis (histolysis and histogenesis). Active 

 centripetal growth on the part of the trachea? leads to an insinuation 

 of their terminal cells into the muscle-fibres, for instance, where these 

 tracheal cells play an important role in histolysis, — a role partly me- 

 chanical, probably also chemical, but unaccompanied by phagocytosis. 



Digestive Function in Insects.§ — A. Porta has examined a 

 number of species of various orders, and concludes that the most im- 

 portant agents in the digestion of insects are the glandular folliculi of 

 the gastric cells, of the villous region, and of the mid-gut folds. These 

 possess both a pancreatic and an hepatic function, and are consequently 

 hepato-pancreatic glands. Their secretion acts by the transformation 

 of albumen into true peptones, by the breaking up of neutral fats into 

 glycerin and fatty acids, by the solution of fatty acids directly broken 

 up by bile, forming an acid liquid capable of emulsifying. 



Biology of Stingless Honey-Bees of Brazil. || — H. v. Ihering com 



* Arch. Sci. Phys. Nat., xvi. (1903) pp. 585-8. 



t Op. cit., xvii. (1904) pp. 110-2. 



X Comptes Eendus, cxxxviii. (1904) pp. 300-1. 



§ Anat. Anzeig., xxiv. (1904) pp. 97-111. 



|| Zool. Jahrb., xix. (1904) pp. 180-287 (13 pis.). 



