182 ENTOMOLOGY FOR MEDICAL OFFICERS 



open. The larva has two pairs of mouth-hooks — a small, 

 straight, median pair, and a large, divaricated, lateral pair. 

 The eggs are attached to the hairs of the destined victim, by 

 whom they are probably licked off. The resulting larvae attach 

 themselves to the wall of the stomach or intestine by their 

 mouth-hooks, their heads becoming at last fairly embedded 

 in inflammatory pockets of the mucous membrane. When 

 the larvae are full grown they lose their hold, and are 

 eventually passed with the droppings, whence they reach the 

 ground, where they pupate. 



CEstrus. The larva lives in the nasal passages and 

 neighbouring sinuses of the sheep and some other Ruminants. 

 In the adult fly the 4th longitudinal vein bends abruptly 

 forwards so as to close completely the ist posterior cell. 

 The larva has a single pair of mouth-hooks ; its ventral 

 surface is flattened, and its dorsal surface is convex and 



Fig. 71.— Macaw-worm ; Larva of DermatoyAa. 



transversely wrinkled or tubercled. The eggs are laid on the 

 victim's nose and the newly hatched maggots are said to 

 creep up ths nostrils. When the maggot is full grown it 

 drops or is sneezed out. 



Hypoderma. The larva forms inflammatory tumours 

 beneath the skin of various domestic animals. In the adult 

 fly the 4th longitudinal vein bends forwards and there are 

 no vestiges of maxillary palps. The larva has no mouth- 

 hooks. The eggs are laid on the hairs of the victim, and it 

 has been supposed that the newly hatched maggots bore 

 through the skin ; but Curtice gives reasons for believing 

 that the eggs or young maggots are ingested by the victim 

 and reach their destination under the skin by an internal 

 route. When the maggot is full grown it pierces the skin 

 and leaves its "host" in order to pupate. 



Dermatobia. The larva is a subcutaneous parasite of 

 various domestic animals and also, very commonly, of man, 



