1916] Biology of Aquatic Lepidoptera 183 



tips of the mandibles are also turning brown. At the end of the 

 ninth or the beginning of the tenth day, the outlines of the com- 

 plete caterpillar are visible through the egg capsule. It is coiled 

 upon itself, the caudal end reflected around the head, and the 

 dorsal surface usually turned from the surface of the leaf. The 

 dark, chitinized head capsule and prothoracic shield are the 

 most conspicuous parts. The intersegmental grooves are visible 

 to a slight degree. The abdomen and the two posterior seg- 

 ments of the thorax are devoid of dark color or markings. At 

 this stage, the mandibles are observed to be in active motion and 

 contractions of the body preHminary to hatching are evident. 



The Larva (PI. VIII, Fig. 11). 

 First Instar. — Larva small; length about 1.4 mm. ; maximum 

 diameter of head 0.25 mm. Body whitish; translucent; head 

 and prothoracic shield very dark-brown and heavily chitinized; 

 remainder of body devoid of dark- color and quite flexible. No 

 "tracheal gills. Principal setas as in figure 11. Anal set« 0.14 

 mm. long. Dorsal surface of segments often showing transverse 

 folds and wrinkles. Prolegs with hooks arranged in transverse 

 ellipse; usually 22-24 hooks on each body proleg; about 7-9 

 hooks on anal prolegs. 



Case-making.—SmsiW, elHptical cases, 2.5-3 mm. long, are 

 constructed soon after hatching. They may be attached or 

 independent and the leaf material may be cut from the periphery 

 or from the middle of the leaf. The young larvae show a very 

 distinct tendency to remain on the lower sides of the leaves 

 where all of the work of excising pieces of leaves is done. 

 Cases are outgrown and new ones constructed, much as has 

 been described for A^. maciilalis, and they seem to serve similar 

 functions. Attached cases usually occur on the lower side of 

 the supporting leaf. 



Food. —Vsicksird. ('84, p. 825) found his supposed larva of 

 N. icciusalis making cases from the leaves of Menyanthes tri- 

 foliata. Forbes ('10, p. 226) reported his specimens on Pota- 

 mogeton and states that they would not eat Lininanthemum. 

 Miller ('12, pp. 127, 130) found caterpillars feeding on Pota- 

 mogeton natans and states that they may also work on Marsilia 

 quadrifolia. The egg masses, larvae, and pupas occur predom- 

 inantly on Potamogeton natans in the Douglas Lake region, 



