230 NATURAL HISTORY OF AQUATIC INSECTS CH. 



protection is wetted, full of water, and fixed. The 

 larva at this time excavates the leaves of Potamogeton, 

 scooping out the soft green substance for its nourish- 

 ment. It moults several times, without any import- 

 ant change in its form or habits. The cold season 

 comes round, and there is still no change, except 

 that the larva feeds less. The following April it 

 begins to feed actively again, and makes a fresh 

 sheath, but still its mode of respiration remains 

 unchanged. In May and June, it for the first time 

 begins to make sheaths filled with air, and its cuticle 

 is now provided with long conical prominences, in- 

 terspersed with smaller ones, which act like velvet, 

 and prevent the surface of the body from being wetted. 

 The spiracles now open for the first time, and the 

 larva breathes the enclosed air. After this it moults 

 once or twice more before undergoing pupation. 



Buckler 1 has related the history of Hydrocampa 

 stagnata. The larvae feed on the Bur-reed (Spar- 

 ganium), riddling the pith with holes, and biting away 

 the sides of the leaves. They hibernate in the cold 

 months, begin to feed again in April, and emerge as 

 Moths in the height of summer. The full-grown 

 larva is -J in. long, and tapers both ways from the 

 third segment. The pupal sheath is made of bits of 

 leaf woven together, and moored to a floating leaf. 

 It lies horizontally, either partly or entirely submerged. 

 Sheaths are also attached to submerged parts of the 

 plant. Inside the sheath is a cocoon of white silk, 

 quite dry and filled with air, which closely invests 

 the pupa. 



1 Entom. Monthly Mag., Vol. XIV. (1877-8), pp. 47-103. 



