146 BLOOD-SUCKING INSECTS 



poison gland, duct and reservoir similar in character to 

 those recorded as being present in certain other species 

 of IchneumonidcB.' In a letter to Nature of 24th 

 November 1921, Dr. Gahan quotes from a paper by 

 M. R. du Buysson (Revue d' Entomologie, vol. ii. p. 

 257, 1892), in which he states that he has often been 

 stung by Ichneumonidce of different kinds, including 

 Ophion, and 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 

 brought to my notice in my own house the person who 

 had been stung was young, and the sting caused con- 

 siderable inflammation and hard swelling which took at 

 least twenty-four hours to subside. ' In M. du Buysson's 

 case,' wrote Dr. Gahan, 'the insect had always been 

 held in the hand or otherwise irritated before it 

 attempted to sting, and this seems to be the general 

 experience. He was never puzzled to divine the pur- 

 pose of the sting, regarding it, no doubt, simply as an 

 act of self-defence ; and that is the explanation which 

 I would venture to suggest in reply to Sir Herbert 

 Maxwell.' That explanation, however, does not solve 

 my difficulty. The persons whose experience with 

 Ophion I have recorded, were in bed and asleep when 

 they were stung, except the young lady who was stung 

 on the arm when reading in bed, and saw the creature 

 in the act. The sleepers may have irritated the 

 flies by involuntary or semi-conscious movements ; 

 but the young lady in question was wide awake and 

 assures me that she was not aware that the creature 

 was on her arm till she felt the stab, saw it 



