110 Dr. H. Dewitz on Rudimentary 
thickenings of the hypodermis ; in the full-grown larva the 
wing appears as a crescentiform lobe standing free from the 
hypodermis and between that and the chitinous membrane. 
The wing-rudiments grow directly outwards, and do not le, 
as in the Lepidoptera and Phryganeide, in sac-like diver- 
ticula. As these wing-lobes are placed under the chitinous 
membrane until the passage to the pupa state, it follows that, 
after the appearance of the wing during the larval existence, 
no ecdysis takes place. Of the hind wings no trace is to be 
seen; the hypodermis on the sides of the third thoracic seg- 
ment is just as thin as on the other parts of the body. It is 
only when the animal spins up* that a semicircular thicken- 
ing of the hypodermis is formed on each side of the third 
thoracic segment. As always in the formation of the imaginal 
disks, a fracheal and a nervous branchlet run to the spot, 
and probably furnish the incitement to the multiplication and 
accumulation of the hypodermal cells. Some time after the 
spinning-up we find the fore wing as a long flat lobe lying 
beneath the old chitinous membrane of the larva, and reaching 
down nearly to the legs. It is widened in its basal part, and 
pointed at the oppositeend. At this time a halfmoon-shaped 
flat lobe has grown out of the thickening on the sides of the 
third thoracic segment, agreeing exactly in structure and form 
with the earlier formed halfmoon-shaped fore wing of the full- 
grown larva. 
The old chitinous skin of the larva is thrown off; and the 
wings, like the other members, come freely into view after a 
new chitinous membrane has been secreted over them as over 
the whole body. 
In the pupa the fore wing is of considerable length, while 
the hind wing lies on the side of the third thoracic segment in 
the form of a very minute freely projecting scale. In the 
fully developed beetle I could detect no trace of the hind wing ; 
and should any thing of the kind be discoverable, it will be at 
the utmost a minute chitinous wart, for the production of 
which an imaginal disk with trachez and nerves can never 
have been necessary. 
While the fore wing, therefore, already occurs in the half- 
grown larva, the rudiment of the hind wing only shows itself 
much later, when the animal is already on the point of termi- 
nating the larval stage. ‘That these rudiments of hind wings, 
occurring only in the last larval stage of all and in the pupal 
* For this purpose a thread is drawn out of a gland situated in the 
neighbourhood of the anus, and with this the animal fastens together 
small particles of bran, 
