THE STINGING OF AN ICHNEUMON FLY 17 



THE STINGING OF AN ICHNEUMON FLY. 



By Right Hon. Sir HERBERT Maxwell, Bart, P.C, F.R.S. 



In the last four or five years persons living in my house 

 have complained of being bitten or stung, they knew not 

 which, by a yellow " fly " in late summer and early autumn. 

 The wounds were always inflicted at night, and caused 

 painful irritation and large, hard swelling. I sent specimens 

 of this insect to Dr Gahan of the British Museum and 

 W. J. Gordon of Corsemalzie, who agreed independently 

 in identifying it as OpJdon lutciis, one of the larger 

 Ichneumonidse. Dr Gahan informed me that this is one of 

 the few Ichneumonidse which are known to sting; that the 

 wound is inflicted by a sharp process at the end of the 

 ovipositor, but that it was doubtful whether the fly possesses 

 anything in the nature of a poison gland. 



It seemed to me almost certain that some irritant must 

 be injected with the sting, because a simple stab like that of 

 a needle v/ould not cause the painful swelling which followed 

 the attack in every case brought to my notice, and which 

 did not subside in less than twenty-four or thirty-six hours. 

 Dr Gahan was therefore so obliging as to request Dr James 

 Waterston to dissect a fresh female Ophion luteus^ and this 

 examination resulted in the discovery of "a poison gland, 

 duct, and reservoir similar in character to those recorded as 

 being present in certain other species of Ichneumonidas." 



So far, my surmise as to the nature of the sting has been 

 confirmed ; but it puzzles me to divine what is Ophton's 

 purpose in stinging human beings without provocation. 

 In a letter published in Nature of 24th November 192 1, 

 Dr Gahan refers to a paper in the Revue d' Entomologie, 

 vol. ii., p. 257 (1892), in which M. R. du Buysson states that 

 he has often been stung by Ichneumonidse of different kinds, 

 including Ophion ; but that the pain and inflammation from 

 the sting lasted only a short time. Individuals vary much 

 in their susceptibility to sting poisons. In every case that 

 has come under my notice the victim has been less than 

 121 AND 122 ' C 



