6 



Fig. &.—Hypoderma lineata — 

 ovipositor of female; a, from 

 side; 6, tip, from below — en- 

 larged (from Insect Life) . 



region about the hoof and flanks of the animal. As seen from the 

 examination of our material, the egg, as soon as deposited, has the 

 larva already formed in it, and it is probable that the young larva 

 escapes from the egg at the moment it is con- 

 veyed to the mouth, the pressure and moisture 

 of the tongue facilitating its escape. The egg, 

 at any rate, splits readily at the anterior end, 

 and the young larva being conveyed into 

 the mouth soon penetrates the esophagus by 

 means of its strong spines, which are repre- 

 sented in the illustration (fig. 5,e,h). These 

 young larviv have been found in the walls of 

 the esophagus, and it is not until about the 

 end of December that they appear in any 

 numbers in the back. 



After penetrating the esophagus the larva 

 soon moults and assumes a nearly smooth sur- 

 face (fig. 7), and for several months wanders 

 through the connective tissue of its host between the skin and the 

 flesh, penetrating gradually along the neck and ultimately reaching 

 a point beneath the skin in the region of the back. In the meantin":e 

 all traces of the larvne or attending inflammation disappear from the 

 region of the esophagus. The ''lick," according to 

 Dr. Curtice, is nothing more than an eft'usion of 

 serum in the connective tissue caused by the inflam- 

 mation induced by the wanderings of the young 

 grubs. 



When the final position in the back is reached, 

 the larva moults again, becomes more spiny, and 

 penetrates or bores a hole through the skin, caudal 

 end first, through \\hich it gets air for respiration 

 at this stage. At this time the anal spiracles, or 

 breathing pores (fig. 8, d,f), are nuich more promi- 

 nent than they were during the long period of the 

 wandering life of the larva, when respiration must 

 necessarily be very limited. The larva now develops 

 much more rapidly, subsisting on the pus and bloody 

 serum which its presence beneath the skin induces. 

 The final moult soon follows, which brings it to the 

 form that is commonly seen by stockmen (fig. 8, g, i). 

 Wlien full grown, the larva has a length of more 

 than an inch and is rather robust and of a yellowish-white color. It 

 works its way out by means of its strong spiny covering through the 

 hole which it has previously used as a source of air, drops to the ground, 

 which it may or may not enter, ])ut, at any rate, contracts and hardens, 



Fig. 7. — Hypoderma 

 lineata — second 

 stage of larva from 

 esophagus; a, larva; 

 h, enlarg.ement of 

 cephalic segments, 

 end view; c, mouth 

 parts; d, enlarged 

 end view of anal seg- 

 ment, showing spira- 

 cles and spines (from 

 Insect Life). 



