174 ENTOMOLOGY 
size, but they are still like a piece of wet cloth, without con- 
sistency and firmness, and as yet entirely unfit for flight, but 
after one or two hours they become sufficiently stiff, assuming 
the beautiful form characteristic of the species.” (Trouvelot. ) 
The expansion of the wing is due to blood-pressure brought 
about chiefly by the abdominal muscles. In the freshly- 
emerged insect, the two membranes of the wing are corru- 
gated, and expansion consists in the flattening out of these 
folds. The wing is a sac, which would tend to enlarge into 
a balloon-shaped bag, were it not for hypodermal fibers which 
hold the wing-membranes closely together (Mayer). Sama 
cecropia also uses a dissolvent fluid; Tropea luna, Philosamia 
cynthia and others cut and force an opening through the cocoon 
by means of a pair of saw-like organs, one at the base of each 
front wing. 
Hypermetamorphosis.—In a few remarkable instances, 
metamorphosis involves more than three stages, owing to the 
existence of supernumerary larval forms. ~ This phenomenon 
of hypermetamorphosis occurs notably in the coleopterous 
genera Meloe, Epicauta, Sitaris, Rhipiphorus and Stylops, in 
male Coccidee and several parasitic Hymenoptera. 
In Meloe, as described by Riley, the newly-hatched larva 
(triungulin form) 1s active and campodea-form. It climbs 
upon a flower and thence upon the body of a bee (Antho- 
phora), which carries it to the nest, where it eats the egg of 
the bee. After a moult, the larva though still six-legged, has 
become cylindrical, fleshy and less active, resembling a lamelli- 
corn larva; it now appropriates the honey of the bee. With 
plenty of rich food at hand the larva becomes sluggish, and 
after another moult appears as a pseudo-pupa, with function- 
less mouth parts and atrophied legs. From this pseudo-pupa 
emerges a third larval form, of the pure eruciform type, fat 
and apodous like the bee-larve themselves. After these four 
distinct stages the larva becomes a pupa and then a beetle. 
Epicauta, another meloid, has a similar history. The t- 
ungulin (Fig. 217, A) of E. vittata burrows into an.egg-pod 
