198 NATURAL HISTORY OF AQUATIC INSECTS CH. 



cess, once thought to be peculiar and unique, exhibits 

 gradations too, and passes by many intermediate 

 steps into a mere moult without change of shape. 

 To trace and study these gradations is one of the 

 most interesting of the biological problems cf the 

 future. Those who attempt to connect the Nemocera 

 with the Muscidae will find that Stratiomys is an 

 important link, illustrating as it does the origin of a 

 change which has profoundly modified the life- 

 history. 



The eggs are said to be attached in overlapping 

 rows to the underside of aquatic plants. 



THE RAT-TAILED MAGGOT (ERISTALIS). 



The naturalist who comes across the Rat-tailed 

 Maggot, a common inhabitant of stagnant pools, 

 especially such as are foul with decaying organic 



i 



matter, should turn at once to that memoir by 

 Reaumur in which he speaks of " two-winged Flies 

 which resemble Bees, Wasps and Hornets." For the 

 sake of those who have not Reaumur at hand I will 

 give the substance of his remarks, but I cannot hope 

 to keep any of the charm of the original. Reaumur 

 discourses in a leisurely way, talking freely of his 

 personal experiences, and handling his subject with 

 the light and amusing manner of an accomplished 

 writer, who must needs be clear, but above all things 

 hates pedantry. It is hard upon so pleasant an 

 instructor that he should be compressed until all' his 

 individuality is lost, and those who can should by all 



