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XVI.— MEEMIS PAEASITIC ON ANTS OF THE 



GENUS LASIUS. 



By W. C. Ckawley, B.A., F.E.S., F.R.M.S., and 

 H. A. Baylis, M.A., D.Sc, F.Z.S. 



(Read November 16, 1921.) 

 Twelve Text-Figures. 



I. Account of the Occukrence of the Worm and 

 ITS Effect on its Hosts.- — W. C. Crawley. 



It was hoped to give in tliis paper a complete account of the 

 life-history of the parasite, but the evidence obtained after nearly 

 a year's continuous observation suggests that it may possibly be 

 longer than was anticipated, and we have therefore thought it 

 better to give the results already obtained, with the hope of adding 

 to them later on. 



There is a fair amount of literature dealing with the infestation 

 of ants by nematode worms. W. Gould, whose little book, " An 

 Account of English Ants," published in 1747, contains many shrewd 

 observations on the habits of these insects, says, " Amongst other 

 incidents that tend to lessen and destroy Ant-Flies " (by this he 

 means the males and winged females) " it is observable that 

 abundance of them are demolished by a white and lonr>' kind of 

 worm, which is often met with in their bodies. You may 

 frequently take three from the insides of the large, but seldom 

 more than one from a small Ant-Fly. These worms lie in a spiral 

 form, and some of them may be extended half an inch." As will 

 be seen below, Gould's account, as far as it goes, is remarkably 

 accurate. By the " small ant-flies " he presumably means the 

 males, as he is speaking of the common yellow ant, Lasius fiavus, 

 but it is possil^le he may be mistaken here, as no Mermis has 

 since been found to be parasitic on the male ant of this species. 

 Gould's worm was subsequently named Gordius foi'tnicarum by 

 Diesing, but no description of it appears to exist. Forel (1874) 

 mentions having found nematodes in the abdomen of L. flavus, 

 and refers to Gould's account. A small worm was found in the 

 labial glands of Formica fusca by Janet (1893, 1894, 1897), and 

 in the pharyngeal glands of F. rufa and L. fiavus by the same 

 author, and this latter form was described by de Lacaze-Duthiers 

 under the name of Pelodera janeti, and later referred to Ehabditis. 



