79 



This is the normal position of these parasites in general, for the 

 respiratory apparatus which is attached to the candal portion, close 

 to the anus, is placed near the opening originally made by the sting of 

 the parent fly, in order that they may be as close as possible to the 

 atmosphere. When the larv« were extracted they wriggled quite 

 actively in their vermicular movements, and continued to move untd 

 they were embalmed in the cell five or six hours after their extraction. 



On microscopicjil examination of the most perfect specimen (with a 

 low- power three quarter objective, B. and L., ej'e-piece B.) a remarkable 

 appearance is presented. The major portion of the parasite is seen to 

 consist of an elongated, pyriform, tuberose, or exaggerated clavate body, 

 apparently concave on the ventral aspect and convex dorsally, termi- 

 nating in a long, tapering, glabrous, elongated-pyramidal extremity. 

 The broader and truncated part of the larva is opaque, and none of the 

 contaiued organs can be distinguished. The external surface presented 

 the curious appearance which is well displayed in Fig. 10 (a aud b). 



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Fig. 10.— One of the larvae viewed in its ventrat (a) and dorsal (b) aspects. At a is shown the ventral 

 aspect aud the appearance of the cephalic and caudal extremities, also the three rows of spines 

 single below, and the point where the double dorsal rows end ; b gives the dorsal view and ^how^ 

 that the three rows of spines single below are double above. Hair line between indicates the 

 natural length. (From drawings made for the author by courtesy of the U. S. Entomologist.) * 



Corresponding to the three dark zones distiuctly outlined with the 

 naked eye are seen three double rows of black booklets or spines, which 

 are distinctly shaped, when examined carefully, like the thorns of a 

 rose stem. They are lamelliform, sharply pointed at the ends, and are 

 curved and directed (the majority) towards the caudal extremity, so 

 that, if embedded in the tissues lining the larval sinus, they would ofter 

 a resistance to caudal traction in direct ratio to the force employed. 

 j This arrangement is manifestly calculated to assist the larva in retain- 

 I ing its position m the subcutaneous tissues, and especially in prevent- 



