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). Samia 

 cccropia also uses a dissolvent fluid; Tropaa luna, Philosainia 

 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 hyper metamorphosis occurs notably in the coleopterous 

 genera Meloe, Epicauta, Sitaris, Rhipiphorus and Stylo ps, in 

 male Coccidse and several parasitic Hymenoptera. 



In Meloe, as described by Riley, the newly-hatched larva 

 (triungulin form) is 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 cruciform type, fat 

 and apodous like the bee-larvse themselves. After these four 

 distinct stages the larva becomes a pupa and then a beetle. 



Epicauta, another meloid, has a similar history. The tri- 

 ungulin (Fig. 217, A) of E. vittata burrows into an egg-pod 



