. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 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 w
. Bulletin of the Department of Agriculture. Agriculture; Agriculture. 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 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
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