A CONTRIBUTION TO THE KNOWLEDGE OF BOT-FLIES. 



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with small hook-shaped, placoid denticles. Posterior margins of segments 2 to 10 

 provided with an armature of irregularly-disposed rows of similar cuticular denticles 

 and sub-ovate, brownish-black, flat scales, the denticles predominating in segments 

 2 to 5 and the scales in the following segments ; segments 11, 12 and 13 devoid of 

 armature. There is a slight medio-dorsal and medio-ventral interruption in the 

 armature of each segment. Two divaricating, cylindrical, fleshy processes arise 

 from the 13th segment, each process containing the prolongation of the main tracheal 

 trunk of its side and bearing at its distal end the posterior spiracle (fig. 6). 



Fig 6. Larva of Gastrophilus intestinalis, x 120. 



Raillet (8), on page 752, quotes Joly as asserting that spines similar to the crown 

 of hooks of the head segment are present on the posteriormargins of segments 2-10 

 inclusive, a view with which we entirely agree. In a footnote, however, this author 

 quotes Brauer's opinion that these spines are more likely attached to the anterior 

 margin of the segments following number 2, as is found in'tke mature]_larvae. 



Gastrophilus nasalis. 



Number of segments 12. Length, 0'829 mm. ; greatest width, - 116 mm. Segments 

 2 to 12 sparsely provided with regularly-arranged, slender, elongate hairs. General 

 colour translucent white, with the exception of the black and brownish yellow of 



Fig. 7. Larva of Gastrophilus nasalis, X 11-1. 



the hooks, denticles and scales of the segmental armature. Slender, paired mouth- 

 stylets directed anteriorly from their articulation with the sclerites of the cephalo- 

 pharyngeal apparatus. Anterior margin of first segment bearing an armament 

 of recurved denticles, the ventral ones strongly developed, elongate and tapering 

 gently to a slender, sharp, recurved point (head-hooks). Posterior margin of segment 

 2 provided with similar placoid denticles, but elongate ones lacking. Posterior 



