348 SUMMARY OF CURRENT RESEARCHES RELATING TO 



protests very emphatically against making theories of metamorphosis 

 in the present state of knowledge. Thus there is prominent phago- 

 cytosis in Mnscids, but in many other insects, such as this Isosoma, there 

 is practically none. 



Respiration of Aquatic Insects.* — P. Portier has described in the 

 larva of Dytiscus a prestigmatic chamber or " chambre de surete," which 

 keeps water from entering the tracheal system. It is a cylinder of soft 

 chitin which opens by a false stigma ; the true stigma, where the spiral 

 thread of the trachea begins, is at the base of the chamber. 



He finds that similar arrangements occur in other aquatic insects 

 that breathe at the surface — larvae of Hydrophilus, Hydrobius, and the 

 like. The apparatus reaches its most perfect differentation in the larva? 

 of Hydrocampa. 



Stigmata of Aquatic Insects.f — P. Portier points out that fatty 

 fluids can enter the stigmata, though water does not. It is a question of 

 capillarity. When oil is put on the stigmata of an aerial insect it soon 

 penetrates the tracheal system, and a caterpillar, for instance, dies in a 

 tew minutes. When the same is done with the larvse of aquatic insects, 

 such as Hydrophilus, the oil is prevented from entering, or if it enters 

 there are various ways in which the insect seeks to avoid the choking 

 consequences. 



Digestion in Larva? of Water Beetles.:}: — P. Portier calls attention 

 to the gluttony of the larva? of Dytiscus, Hydrobius, and Hydrophilus. 

 They eat so much that they sink to the bottom. There they show 

 phenomena of asphyxiation, and they lighten themselves by emitting 

 liquid at the fine tips of the hooks or at their base. The anterior and 

 median part of the mouth is physiologically closed. 



The larva? can inject a large quantity of digestive liquid into their 

 prey. The digestive fluid collects in Dytiscus in a large intestinal 

 cascum ; it has a dark colour, it is neutral or slightly alkaline, it contains 

 a trypsin and probably also a tyrosinase. The poisonous character of the 

 bite seems to depend on a special toxin, but the author has not found 

 the gland. In the larva of Hydrobius there is no caecum, but the 

 digestive fluid accumulates in the rectum. In Hydrophilus the hooks 

 do not seem to be perforated at all. 



Sensorial Papilla? on Proboscis of LepidopteraJ— E. Guyenot 

 describes the varied structure of minute cylindrical papilla?, with a ring 

 at the base, a cone at the tip, and diverse ornamentations, which occur 

 on the proboscis of Lepidoptera. It would be interesting to correlate 

 their variety of number and size with differences in the habits of 

 the insects. 



Excretion during Metamorphosis of Heterogenea.|| — Katharina 

 Samson has studied the conditions of the Malpighian tubules in the 

 metamorphosis of the caterpillars of Heteroyenea limacodes. The 



* C.R. Soc. Biol. Paris, lxvi. (1908) pp. 452-4. f Tom. cit., pp. 496-9. 



X Tom. cit., pp. 379-82. § Tom cit. pp. 525-7. 



i| Zool. Jahrb., xxvi. (1908) pp. 403-22 (2 pis. and 2 rigs.). 



