458 Proceedings of Philosophical Societies. [Dec. 



duals to remain in the nest and take care of the larvas which next 

 year were to renew the population of the colony. 



M. Olivier, member of the Class, has drawn up a memoir on the 

 insects injurious to corn, belonging equally to agriculture and 

 zoology. Hitherto he has communicated only the part relative to 

 the species which attack corn in the blade. M. Olivier describes 

 nine such insects, all belonging to the order of insects with two 

 wings. But he makes known at the same time three species of 

 insects enemies to these, which, by stopping their propagation, 

 diminish the injuries they commit. 



One of the most important questions in the anatomy of insects 

 respects the use of the great vessel which all that class have along 

 the back, and which undergoes contractions and dilatations com- 

 parable to those of the heart and arteries. Malpighi and Swam- 

 merdam gave it the name of heart ; but it appears certain, from 

 the observations of Lyonnet and others, that no branches issue 

 from it ; and M. Cuvier seems to have established, by many proofs, 

 that there is no circulation in insects. M. Marcel de Serres has 

 examined this subject anew. He has satisfied himself, by very 

 numerous observations on the largest insects in the south of France, 

 assisted by all the most delicate instruments that anatomy possesses, 

 that the dorsal vessel does not send off any ramification, that no 

 other contractile vessel exists in the body, and no system of blood- 

 vessels. Insects deprived of the dorsal vessel continue to live several 

 hours, while the scorpions and spiders, which possess a true heart, 

 perish immediately if it be destroyed. The contractions of the 

 dorsal vessel are principally owing to the muscles of the back placed 

 along its sides ; but the tracheae and nerves exercise a considerable 

 influence on it. The humour which it contains frequently appeared 

 of a colour analogous to that of the fatty matter, which always fills 

 a part of the body ; it is scarcely liquid, especially in the voraceous 

 larvae. The diameter of the vessel is more equal in those larvae in 

 which the fat is more equally distributed, and the inequalities of its 

 different parts are proportional to those of the fat in the correspond- 

 ing parts of the body. The nerves and tracheae are more abundant 

 in the dorsal vessel of larvae than in 1 that of perfect insects ; its 

 contractions are also stronger, but less frequent. _ From these and 

 some other facts the author considers himself entitled to conclude 

 that the function of the dorsal vessel is to produce fatty matter, and 

 that in order to produce this substance it absorbs a part of the 

 nutritive liquor contained in the cavity of the body through the 

 coats of the intestine, and that it then transudes it through the 

 interweavings of the adipose tissue where the fat is completely 



formed. 



M. de Serres has introduced into his memoir some valuable obser- 

 vations on the varieties of structure of the tracheae in different families 

 of insects, among which we may remark particularly those which 

 relate to the mechanism of the vesicular tracheae. He terminates 



