84 THE EARLY STAGES OF TABANID^ 



bifurcating into the somewhat tapered cylindrical mandibles on its anterior half. 

 The maxillae are traceable to two-thirds of the distance from the tip to the base 

 of the head, scarcely tapering, bent obliquely downward at two-thirds of the 

 way to their tip, and obliquely truncate at tip. On the anterior margin of ven- 

 tral segments four to ten, in the living insect, is a row of six large fleshy roundish 

 tubercular retractile pseudopods, the outside ones projecting laterally, and each 

 at tip transversely striate and armed with stout bristly pubescence; on the ante- 

 rior half of ventral joint eleven is a very large, transversely oval, fleshy, whitish, 

 retractile proleg, with a deeply impressed, longitudinal stria. On the anterior 

 margin of dorsal joints four to ten is a pair of smaller, transversely elongate, re- 

 tractile, fleshy tubercles, covering nearly their entire width, armed like the 

 pseudopods, but not so much elevated as they are. No appearance of any 

 spiracles. Anus terminal, vertically slit, with a slender retractile thorn, 0.05 

 inch long, visible in 1860, but not in 1863. Head, and first segment or two, 

 retractile." 



When handled, the larva is, according to Walsh, "very vigorous and 

 restless," and burrows with great strength between the fingers, and 

 even on a smooth table walks as fast as any ordinary caterpillar, 

 either backwards or forward; when placed in a vessel of water it 

 swims vigorously, twice the length of its body at every stroke, by 

 curving its tail around laterally, sometimes to the right, sometimes to 

 the left, so as to touch the side of the fourth or fifth joint, and then 

 suddenly lashing out with it. In such a vessel it always keeps close 

 to the surface, and at the end of every stroke, and also when in re- 

 pose, elevates the anal slit out of the water, on which occasion Walsh 

 once saw a bubble of air attached to it. In the breeding jar the 

 larva scarcely ever comes to the surface, but burrows among the 

 decayed wood, aquatic plants, etc. 



The larva described by Walsh differs, according to him, remarkably 

 from the one described by Degeer {Tabanus bovinus L.), in having 

 ventral pseudopods as well as dorsal ones. Walsh says that it might 

 be supposed that the dorsal tubercles were branchial, "but for the fact 

 that they are found in the earth inhabiting species described by De- 

 geer," and that like the aquatic larvas of Pnonoxyphon discoideus 

 Say (Coleoptera) it has a branchial apparatus issuing from the anus, 

 and the short retractile anal thorn, observed in 1860, was the form 

 assumed by this structure when out of the water. This assumption 

 by Walsh is partly confirmed in so far as the terminal spine con- 



