Entomology of the Illinois River. Vll 



face, secretiug themselves in the retreat thus formed, 

 and feeding upon the substance of the leaf. When a 

 little older, the larva cuts loose the portion of leaf 

 surface to which it has attached its shelter, and is 

 thereafter found traveling about like a case-worm in a 

 lens-shaped case, formed of two irregularly oval convex 

 pieces of green leaf attached at their sides and open at 

 the ends. In the larger cases made by older larvae the 

 posterior end is narrowed, giving the case an ovate 

 shape, or is even provided with a projecting median 

 lobe, like the neck of a bottle, in which rests the pos- 

 terior end of the larva [Fig. 11]. A case found by us 

 in September had one side made of the fronds of Lemna 

 trisulca, and another was entirely formed of these little 

 fronds. The pupal case is similar to that of the larva, 

 but is smaller, oval, and more convex, and the edges 

 are apparently strongly webbed together throughout, 

 though the anterior end is easily parted, revealing an 

 oval cavity with closely woven silken walls. When quite 

 young, the larva is submerged and water-breathing, but 

 soon fills its case with air and breathes it directly. In 

 this respect it differs from Paraponyx, which remains 

 submerged througiiout its larval life. 



The larvae [Fig. 10] were common in July and mostly 

 reached the pupal stage during the first part of August, 

 those seen towards the last of this month being fewer 

 in number and mostly full grown. They continued to 

 appear, howevei-, and still occurred in the collections 

 made in October. Tlie presence of more young larvae 

 than usual was noted Sept. 20, and a young example 

 taken in Flag Lake Mar. 23 seems to be of this species. 

 A few imagos were seen at the time the first eggs were 

 collected, and they continued to increase in numbers, 

 becoming most abundant in August and September, 

 when they were quite common on plants over water and 

 often settled abundantly upon the sides of our row- 

 boats. A few were seen in October. They emerged in 



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