ANNUAL REPORT OF NEW YORK 
792' 
MIDGE. LARVA. THE CASED LARVA. 
now 'become what is termed a cased larva. It is analogous to a 
pillow enclosed in a pillow-case. Its outer skin forms a thin and 
nearly transparent case, a bladder-like pod or bag, within which 
the worm lies. And the yellow worm it is plainly to be seen 
does not fill this case. A whitish transparent space is seen 
sometimes at one, sometimes at both ends, extending beyond the 
ends of the yellow worm inside. This transparent portion in¬ 
creases in length as the worm within becomes more dried and 
shortened, whereby it sometimes forms a fourth or a third of the 
total length. And thus the worm will remain dry, stiff and 
quiescent in this case, for several months, without any further 
change and without losing its vitality. But on placing it upon 
a wet cloth it revives. It absorbs the moisture and hereby 
swells out to its former size and becomes soft and flexible. The 
following note of an examination of one of these cased larvse 
when it was revived by moisture and beginning to move again, I 
here present. “With the magnifier I see it swells itself out to 
almost till the case, and then contracts, leaving a large vacancy 
at one end of the case, and then expands itself again. I now 
place it in a drop of water on glass, and examine it under the 
microscope. The inclosed worm has the same appearance and 
parts as in the figure of the moving larva (fig. 12), and the tip 
at times shows the four sharp teeth and the round concavity the 
same as figured (fig. 14). I see the transparent case is frac¬ 
tured, whereby it has an irregular opening on one side near its 
fore end, and the inclosed worm protrudes its head and horns 
from this opening, and feels around, slowly and cautiously, as if 
fearful the same violence which caused this rent might still be 
lurking there to do it further injury; and on the slightest dis¬ 
turbance it draws back into the case again. Next I notice it 
with the point of its head feeling all about the head end of the 
case forward of the opening, as if to ascertain if there was any 
other injury there. Then again it protrudes its head from the 
opening, examining around on the outside as before. It repeats 
these movements several times, till I beooine weary of noticing 
them.” The worm eventually crawls out of this case or outer 
skin and disappears. 
Now that we have seen this larva under its three different 
forms of a quiescent, a moving and a cased larva, and have 
observed how readily it crawls when wet or placed on a surface 
