On Inflation in Insects. 



By T. A. Chapman, M.D., F.E.S., &:c. Read November 13///, 1902. 



In promising the Secretary that this should be a very short paper 

 it was evident that it would not do to give it a long title. It 

 becomes, however, very probable that the result is considerable 

 ambiguity as to what the paper is about. I hasten therefore in the 

 first place, \n order not to disappoint too seriously the expectations 

 of those members of the Society who may interpret it by the light 

 of the financial jargon they learn in their business experience in the 

 City, that I do not propose to say anything about the prices given 

 occasionally for Goliath beetles, Papilio antimachus, great coppers, 

 or other rare bugs, or as to the circumstances that govern such 

 eccentricities. Nor do I intend to refer to the conscious pride with 

 which many butterflies and other beautifully coloured insects 

 disport themselves. 



The title is to be taken more literally ; the inflation I propose to 

 call your attention to is that of the insect's body with air. Even so 

 I have still further to define my position. Nearly all insects that 

 fly — that is, nearly all insect imagines — possess large air-spaces in 

 their bodies. In some the greater part of their bulk is fictitious^ 

 being due to large air-spaces within. Many Hymenoptera^ — the 

 common wasp and the hive bee, for example — possess an abdomen 

 that may be telescoped almost into the basal segment and extended 

 to great length in a few seconds. This is managed by filling or 

 emptying great air-sacs within the abdomen. As this form of infla- 

 tion is not my subject this evening I do not feel called on to discuss 

 how far this may be to secure a proper specific gravity and balance 

 during flight, how far to correspond with varying contents of honey 

 or other food, and what may be its use in assisting the active 

 respiration necessary to insects making such strenuous muscular 

 efforts as their flight requires. 



The inflation I hope to interest you in for a moment occurs only 

 once or twice during the life of each individual, to secure certain 

 very definite objects. I know more of it in Lepidoptera than in other 

 orders, but believe it occurs in nearly all the orders. 



My first definite observation on this subject of which I have 

 any record, though I certainly had previously some general ideas, 

 derived from the Lepidoptera, was made on a Dipteron, Tipula 

 flavolineata, a species of daddy-longlegs whose larva lives in rotten 

 wood. My notes on it are in the " Ent. Mo. Mag.," vol. vi, p. 31 

 (1869). In this case, when the imago emerges from the pupa it is 



