ZOOLOGY. 447 



fly is metallic blue ; its head comparatively large, swollen, 

 and of a bright orange red. It lives in dark places, on offal, 

 a sombre light issuing from its phosphorescent head. This 

 statement of Macquart is probably taken originally from 

 Robineau Desvoidy. 



M. Jousset de Bellessure gives an extraordinary account 

 of the mode in which LibeUula depressa expands to its full 

 size, and extends its wings after quitting the pupa skin. Af- 

 ter describing the well-known process of the emergence of the 

 insect, he inquires by what mechanism does the insect inflate 

 itself and increase its volume to such an extent that after 

 issuing from its little envelope it suddenly becomes double 

 its former size. He states that at this time the function of 

 respiration, which is very active in the adult dragon-fly, is 

 not yet set up. There are no movements of inspiration and 

 expiration ; the abdomen is cylindrical, and the deep fold in 

 the ventral surface of the abdomen, which he regards as es- 

 sential to respiration, is not yet in existence. On dissection, 

 the air-sacs of the body are found to be empty and flaccid. 

 Nevertheless, the inflation of the dragon-fly is effected by 

 air; and if the body is cut through with a pair of scissors, it 

 collapses in a moment like a balloon. By taking suitable 

 precautions, and dissecting the animal under water, it is 

 found, he says, that the digestive tube here performs a most 

 unusual physiological part. It is so much distended that it 

 absolutely Alls the whole interior of the body, pushing the 

 other oro-ans against the integuments. Under the influence 

 of this energetic pressure the blood is pressed forcibly tow- 

 ards the periphery, distends the eyes, and gives the head 

 its definite form ; then passing into the wing, between the 

 two membranes which up to this time are separate, as M. 

 Blanchard has described them it accumulates in the wing, 

 unfolds it, and circulates in it, depositing the pigment which 

 is destined to color it. During this time the integuments, 

 which are distended and bathed by the nutritive fluid, ac- 

 quire their proper color and solidity. It is by swallowing 

 the air, and storing it in its digestive tube, says the author, 

 that the LibeUula obtains the force necessary for the accom- 

 plishment of most of its transformations; and he thinks there 

 is every reason to believe that the same thing occurs in many 

 other insects. 



