308 



PSYCHE. 



IJuly— September iSSS- 



6. They molt twice while they are 

 parasitic. I have obseived most closely 

 the molting in Hypoderma larvae of the 

 second stage. In H. diana the pas- 

 sage from this stage [p. 38] to the 

 last one takes place about the begin- 

 ning of February. If in a cutaneous 

 muscle which is richly larded with 

 such larvae the capsules of those larvae 

 whose hinder stigmatal plates have the 

 shape of the third stage, but are still 

 clear yellowish-brown, are carefully 

 slit open, the skin characteristic of the 

 preceding stage, with the many little 

 thorns heaped in groups, will be found 

 either still partlv attached to the front 

 end of the laiva or entirely dependent 

 from the cephalic end or folded together 

 along the dorsal side. The process of 

 molting seems to be entirely similar to 

 that in the Mclophagus larvae ; at least 

 Leuckart states that tiie old skin in 

 these is shoved together toward the 

 cephalic end of the larvae and there re- 

 mains attached. The Hypodcrtjia larva, 

 immediately after the molt, is pure 

 white, very soft, and appears naked, 

 since the thorns do not become dark 

 and distinctly separated from their sur- 

 roundings until they harden. 



Three forms or stages are to be dis- 

 tinguished, corresponding to the molts, 

 which forms in Hypoderma, Gastro- 

 philus and Dermatobia show great 

 differences. In the third stage the lar- 

 vae reach their full size, usually change 

 their color and that often very consid- 

 erably, and then first leave their host- 

 animal, crawl away and pupate, after 

 the manner of the muscidae. 



7. This pupation must be consid- 

 ered as a third molting, in which, how- 

 ever, the skin is only detached around 

 the pupa, but is not stripped off, and 

 remains in connection with it by means 

 of four tracheae. The hardened larval 

 skin, or puparium, is burst open at the 

 cephalic end by the emerging fly by 

 means of the frontal bladder tilled with 

 fluid, in the direction of the arcuate 

 sutures in a double manner. Altliough 

 the pupation resembles iieiein that of 

 the m/iscidac in general, vet there oc- 

 curs in one part of the oestridae, i.e., 

 in Hypoderma, a peculiarity which has 

 not been observed before, namelv, that 

 the larva transforms in the puparium 

 in a completely outstretched condition, 

 and this therefore is far larger than the 

 insect which comes forth from it. 



8. So far as they have been observed, 

 thev lead a parasitic life in mammals, 

 and feed upon the juices of these ani- 

 mals. In Hypoderma a blood-red in- 

 testine often shows through, and it is 

 likely that these sometimes suck up 

 blood in addition to the exudation \\ liich 

 immediately surrounds them. 



9. The closely observed larvae all 

 show at first a slow and finally a rapid 

 development, so that there occurs a 

 resting stage which often lasts seven 

 months, between the swarming of the 

 imago and the first visible appearance 

 of the larvae. 



The larvae of the oestridae were for- 

 merly divided into two groups : into lar- 

 vae with oral hooks and those without 

 external mouth-parts. Such a separa- 

 tion is of service in distinguishing the 



