192 



PEACTICAL PARASITOLOGY 



hastened if the dead larva is first pricked in the back with a fine 

 needle. After removal from the fluid the soft body contents may be 

 squeezed out through the needle-hole. Clean water should be added 

 and the manoeuvre repeated until the body cavity is quite empty. 

 The cuticle and its appendages will now be of sufficient transparency 

 to be examined in water. The soft parts are only to be seen in 

 anatomical preparations. 



The larvae of (Estridas, 



a (j[J or Bot-flies, are found in 



d these latitudes in game 



animals and in the domes- 

 tic mammals. Three 

 groups are recognized : the 

 Cuticolce, the Gastricolce, 

 and the Cavicolce. The 

 larvae of several species 

 of Gastrus inhabit the in- 

 testine of the horse; those 

 of Hypoderma bovis are 

 found in abscesses under 

 the skin of cattle ; and 

 those of (Estrus ovis in 

 the nasal cavities of sheep. 

 As a general rule, only 

 larvae in the third stage of development are found. Very little in- 

 formation is forthcoming concerning the young stages and, in some 

 cases, they are quite unknown. In certain species the young larvae 

 inhabit different organs (Hypoderma bovis}. 



The larvae of (Estridae are somewhat larger, otherwise they conform 

 to the general structural organization of the larvae of Muscidae. Slight 

 differences in the body shape, in the mouth-parts, in the arrangement 

 of bristles upon the body segments, and in the structure of the anterior 

 and posterior stigmata, serve to distinguish between species, without 

 reference to the organ or to the host from which the larvae have been 

 taken. 



CEstridae may be cultivated artificially in earth, but only if ripe 

 larvae those, that is, which are on the point of leaving the host in 

 order to become pupae are used. The ripe larvae are recognized by 

 their colour, which changes before they quit the host. 



FIG. 100. Sarcophaga carnaria. a, b, and c, The 

 stigmatic apparatus during the three stages of larval 

 development d, Anal end of a mature larva seen 

 from behind. Magnified. (After Portschinsky.) 



