1910] Forbes—Aquatic Caterpillars O21 
the house, into warmer water, they mostly cut out the portion 
of leaf on which their nests were made, and so made of then 
portable cases, much like those of N. gyralis, but filled with water. 
Pupation took place in the last nest, which was lined with a 
translucent layer of silk, and then showed a distinct central ridge 
from the outside. If the caterpillar was in a portable case (in the 
laboratory), it was anchored to the edge of a leaf. Late in August 
young caterpillars about an eighth of an inch long, or a little 
larger, had the same habits, but very soon the cases were cut 
away, as happened with the first brood in the laboratory, and the 
caterpillars were found to be only on the young submerged leaves. 
Apparently when very young they eat one epidermis and the 
parenchyma of the parts of the leaf forming their nests, but by 
the time they are a quarter of an inch long they feed only outside 
of the nest which is of uninjured pieces of leaf. 
Eggs were laid in captivity, but not in a regular egg-mass. They were oval and 
flattened; .65 x .5 mm., and had no decided longitudinal ridge. Duration of stage 
about ten days. 
Stage I. (From these eggs.) Slightly larger than N. gyralis? described below, 
with proportionately much larger anal sete, without a trace of gills. Head nearly 
.3mm.; length of large anal setee 1 mm. 
Stage II. Not seen; and no sign of leaf-mining was noticed. 
Stage III (?). A transparent caterpillar, essentially like the full-grown ones. 
The maximum number of gill-filaments is two, and the anterior suprastigmatals 
and the last three pedals have but one. Length about 4mm.; head .6 mm. 
Stage IV. Length 4 to 6 mm.; head .4 to .56mm.; maximum number of gill- 
filaments three. 
Stage V. Length 6 to 10mm.; head 1 to 1.5 mm.; maximum number of gill- 
filaments four. (Possibly two stages are confused here, or the wide range in size of 
head may be sexual. 
Last Stage. Length fully extended may reach 25mm.; head 1.5mm. Trans- 
parent, the only appearance of marks being due to the internal organs showing 
through. Head pale chitin-yellow, with darker mouth-parts. The gills are 100 
in number, each with from two to five filaments, as shown in the diagram. 
Segments. 2 SUA aa Se Alby \ Grd 8) SD 
Anterior suprastigmatal: .3..5..2.:2-5-.- BF co ae Se Ay A aie Ay 8) Sl) = 
Posterionsuprastigmatallsser yee ee eee Bi, 4B) 85.6) 65) A, Ai) 4m 
Weatteralls:c cic yeascenys stories clay eape coos Sine 
Anterior intrashigmatalee cecal es = Se Ol OE OMmOr i Onl L Oma 
Posterior infrastigmatal..............-- Say oy GY BOG B  GAG!! SG } - 
