﻿THE CATTLE GRUBS OE OX WAKBLES 



29 



Fig. 9. — Hypodfrnui hovis: First-stage larva. I, Lateral view; II, vemtral view; 

 III, cephalopharyngeal skeleton with spine and mouth hooks ; IV, caudal segment. 

 Ph, Skeleton of pharynx ; //, mouth hooks ; 31, spine ; Tr, air tubes ; P. sp.^ pos- 

 terior spiracles (Carpenter and Hewitt) 



Ventrally segments 2 to 9 are provided fairly con- 

 stantly with a heavy l)and of spines along the posterior 

 border, but it is not uncommon to find specimens in which 

 segment 10 is also armed and others with segment 9 

 naked. The spines on the anterior borders of the seg- 

 ments, ventrally. vary even more, and usually end on 

 the eighth or ninth segment. Laterally the armature is 

 very irregular and rarely extends behind the sixth seg- 

 ment on. the ventrolateral or the foui'tli segment on the 

 mediolateral and dorsolateral areas. iJorsally the arma- 

 ture is almost entirely wanting. The greater p;irt of the 

 anal segment posteriorly is thickly covered with small 

 spines surrounding the posterior spiracles, but the tri- 

 angular spines are no longer present. The two posterior 

 spiracles may be round or very irregular in outline. 

 They consist of a group of circular rings or disks. The 

 color of the stigmal plate is orange or .yellowish brown, 

 and the di.sks are separate or loosely connected in groups 

 but always very distinct in individual outline. The num- 

 ber of disks varies from 12 to over IM). but usually with 

 sjiecimens collected in Texas it is from about IS to 25 

 'na. 14). 



The fourth-stage larva of //. horif< is similar to Ibjit of 

 //. Uncatum, but when grown it is slightly larger. The only 

 ►specific rlistiiitjuisliing cliarjicfers lli:it can be relied upon 

 are the p<^j8terior stigmal plates. In //. hovin the stigmal 

 I)lates are composed of disks or rings Hint are dark brown 

 or black in color, and usuiilly flic wliob; grouji is closely 

 fused togetbcr. Tli(; niniiber of disks in //. hovln i.s 

 usually con.siderjibly higher than in //. Uncatum, running 

 from 29 to above 40, with the nonn.i! number alxjut ."'.2 

 to 37 (fig. IG). 



» /V 



Fig. 10. Ifi/pnrlerma 

 Hnratinii: \'ontral 

 view (if lirst-sl.agei 

 larva. A, IMoutli 

 IkkjUh; /{, aiilcrior 

 HiuracJcK ; C, rcplia- 

 lopliaryngcMl skHo- 

 iTin ; J''n, flat I cued 

 NplncH on IkiimIci' oT 

 no.sti'riof Niiii-aclcH ; 

 /'. sp., iK)St(;r)()r 



SpllMclcK. X 121 



(Lanke) 



