234 NATURAL HISTORY OF AQUATIC INSECTS CH. 



is completely submerged, the emerging Moth must 

 float up through the water. The Moths, which arc 

 by no means uncommon, appear in June, July, or 

 August, and may be seen disporting themselves on 

 the surface of the water. They lay greenish eggs on 

 floating fragments of leaves, and the eggs hatch out 

 in eight days. 



There is, as we have seen, some discrepancy in the 

 accounts of the pupation of Hydrocampa nymph^eata. 

 Some observers have recorded that the pupa-case 

 is attached to submerged leaves, while others have 

 found it fixed to stems well out of the water. But all 

 agree that the pupa-case of Paraponyx is often to be 

 found attached below the surface, and it becomes a 

 question of some interest how the air-breathing pupa 

 can under these circumstances obtain the moderate 

 supply of gaseous air which it requires. A fact 

 contributed by Dr. Schmidt-Schwedt i may furnish 

 the answer to the question. Schmidt-Schwedt found 

 that beneath the pupal cocoon of Paraponyx the 

 leaf of Stratiotes^ is pierced by a number of small 

 holes, which, as thin sections prove, pass into the 

 air-filled spaces which are so common in aquatic 

 plants. It may be that Paraponyx, like Donacia, 

 draws its supply of air, during the pupal stage, 



1 Berl. Eniom. Zeits., Bd. XXXI. p. 332 (1887). The 

 author does not believe that these openings in the leaf are 

 actually employed as a source of respirable air, but his reasons 

 are of a general kind, relating to the excess of oxygen in the 

 gas evolved from a living leaf, and not very convincing to 

 myself. 



^ He calls it by mistake Pistia stratiotes, a very different 

 plant. 



