Mermis Parasitic on Ants of the Genus Lasius. 



357 



weeks it spent most of the time out of sight under the soil, only 

 appearing when the earth became dry. War duties necessitated 

 my leaving home for some months, and the Mermis in consequence 

 died. 



The size of the worms found in these two species of ant varied 

 considerably (see description). In more than one case an ant 

 contained no less than three worms. The illustrations show the 

 relative size of the host and the parasite, also the manner in 

 which the parasite is coiled up in its host. 



My friend Dr. J. Bronte Gatenby very kindly cut a series of 

 excellent sections of the abdomen of a L. alicnus female with the 



Fig. 2. — Normal female of Lasius alienus. 



parasite in situ. These sections, and also the simple dissections 

 of the abdomens of the hosts, show very clearly how considerably 

 the ovaries are reduced in size compared with those of a normal 

 female. The sections also distinctly show the beginning of de- 

 generation of the nurse cells. Both these conditions are directly 

 traceable to the starvation ot the organ caused by the parasite. 

 Other conditions pointed out by Gatenby as caused by the parasite 

 are the hypertrophied tracheie and the almost entire absence of 

 fat-bodies in the host. The Malpighian tubules are normal. 



A careful examination of the ant fails to reveal any external 

 modification except the reduced wings and the distension of the 

 abdomen caused by the presence of the worm. This distension 



