Burrowing 



255 



FIG. 156. A nymph of a burrowing mayfly, Ephemera. (From Annals 

 Entom. Soc. of America: drawing by Anna H. Morgan). 



The digging of burrows requires special tools for mov- 

 ing the earth aside. These, as with land animals, are 

 usually flattened and shovel-like fore legs. The other 

 legs are closely appressed to the body to accommodate 

 them to the narrow burrow. The hind legs are directed 

 backward. The head is usually flattened and more or 

 less wedge-shaped, and often specially adapted for 

 lifting up the soil preparatory to advancing thro it 

 (see fig. 116 on p. 209). 



One of the best exponents of the burrowing habit is 

 the nymph of the may- 

 fly, Hexagenia, whose 

 innumerable tunnels 

 penetrate the beds of 

 all our larger lakes and 

 rivers. It is an un- 

 gainly creature when 

 exposed in open water; 



but when given a bed 

 of sand to dig in, it 

 shows its fitness. Be- 

 sides having feet that 



FIG. 157. The front of a burrowing may- 

 fly nymph, Hexagenia, much enlarged, 

 showing the pointed head, the great 

 mandibular tusks and the flattened 

 fore legs. 



are admirably fitted for 



scooping the earth aside, it has a pair of enormous 



