358 



Transactions of the Society, 



disappears after the emergence of the worm, and the ant has then 

 a normal appearance except for the small wings. The size of the 

 latter varies to a certain extent, a series of L. flavus showing a 

 variation in the upper wing of 4" 6 mm. to 5*3 mm., and one of 

 L. alienus of 5 • mm. to 6 ' 2 mm., whereas the normal wing of 

 the first species measures 9 • mm. in length and that of the latter 

 10-0 mm. The variation in L. niger is 5 '3 mm. to 6'0 mm., 

 the normal wing being 10*0 mm. 



Until 1920 the only two species of ant known as hosts of 

 Merniis in this country were L. fiavus and L. alienus, but in July 

 1920 my friend Mr. H. Douisthorpe found in Cornwall a colony 

 of L. nigcr containing numerous mermithogynes (1921). The 



Fig. 3. — Mermithogyne of Lasius flavus. 



habits of all three species are to a great extent similar. L. fiavus 

 throws up mounds which become covered with grass and may 

 reach a diameter of over 2 ft. and a height of 1 ft., and 

 these nests are generally in meadows. A certain amount of 

 moisture is necessary for these ants, and nests are often found in 

 damp situations, and stones, logs, etc., are often utilized as cover. 

 L. alienus, though equally a hypogieic species, rarely throws up 

 mounds, but is more fond of stones as slielter, and its nests are very 

 frequently in damp situations. L. niger has habits similar to 

 those of alienus, but lives more in the open air, and in damp places 

 will erect earth mounds. All three species have the following 

 important habits in common : they nest underground, preferably 



