8918 Insects. 
separate them. The female is, however, strikingly different; so far 
from being apterous, it is furnished with wings of twice the area of 
those of the male. 
3. Acentropus Newz of Kolenati. This form, from Kolenati’s 
figure, I judge to be distinct. It will there be seen that the insect is 
smaller than A. niveus. The upper and under wings have different 
relative proportions, and the body is shorter and more hairy, whilst a 
very definite difference exists in the two blunt teeth on the hinder 
tibie, of which | cannot detect any trace in A. niveus. It is probable 
that A. latipennis of Méschler will prove to be the female of this 
species. 
The larve of A. niveus may be found, when fully fed (I have failed 
in discovering them earlier), in silken cocoons, which are strengthened 
by small.pieces of the leaves incorporated longitudinally in the fabric, 
and which are placed in the submerged axils of Potamogeton per- 
foliatus and P. pectinatus. The larve are of a light green colour, 
and possess every Lepidopterous character, and make no approach to 
the Trichopterous type. The pupe are of the “ masked” character, 
and the external case enables one to see clearly which will produce 
males and which females. The pupe exhibit three remarkably pro- 
minent spiracles on each side. 
The male imago of A. niveus sits sluggishly on any object that 
protrudes from the water where it occurs, or it flies slowly over the 
surface. I saw it on one occasion deliberately enter the water, and, 
after creeping down a pond-weed stem for an inch or two, it emerged 
again with unwetted wings. This act was probably done in pursuit 
of the virgin female. I regret, although I have bred the apterous 
female, | have never had an opportunity of studying its habits in a 
state of nature; but, from the long tibial fringes which it possesses, 
I presume it to be endowed with active swimming and diving powers, 
to enable it to deposit its eggs upon the food-plant, which, excepting 
in flowering time, is almost always totally submerged. For several 
seasons, owing, I imagine, to floods in July and August during 
previous successive years, I have been unable to find the insect in its 
old haunts. 1 have thus been disappointed in the hope I entertained 
of being able to complete its history from the egg to the imago, and 
hence the cause of the delay in giving my observations to the 
public. 
With regard to the position of Acentropus in nature, the opinions 
of entomologists, as I have stated, have varied very widely. The 
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