305 



the i)res('iit time. It will be remembered that in the summary of tlie life- 

 history of the better kuowu Ox Warble, viz, Hypoderma bovis (Insect 

 Life, Vol. ii, pp. 172-177), the actual mode of ovipositiou was shown 

 to be not absolutely kuoMni, and that between the two oi)])osinc^ views 

 that were held, viz, insertion of the egg in the skin, or its attachment 

 to the skin or to the hair, a number of reasons based on recollection, on 

 the structure of the ovii)ositor and on the structure of the egg, were 

 urged in favor of attachment rather than of insertion. From the struc- 

 ture of the egg Dr. Curtice also drew the conclusion that the egg is at- 

 tached to the hair of the animal, but from the other facts observed by 

 him he also concluded that the young larva' are licked off by the cattle, 

 swallowed or lodged in the back of the mouth or esophagus, and pene- 

 trate the esophageal walls. These conclusions were deduced from tlio 

 presence of the young grubs in the esoi)liageal walls in November, and 

 long before they are found in the backs of the cattle. Later, about 

 Christmas time, they appear suddenly in full force under the skin of 

 the back. The earliest larvje occurring beneath the skin differ in no 

 wise from those found in the esophagus. By the latter jiart of January 

 or the beginning of February all have disappeared from the esophagus, 

 together with all traces of the inflammatory action in that organ scniotice- 

 able in January. The larvie at this stage are able to pierce through the 

 esoi)hagus and wander through the tissues to the back. The wander- 

 ing of the larvpe is further shown, according to Dr. Curtice, by the fact 

 that they have been found near the eleventh rib on the thoracic side, 

 also in the spinal column, in the subcutaneous nuiscles, and connective 

 tissue. Dr. Curtice has also found in the esophageal muscular coats 

 wounds which he believes to have been caused by the larvie in pene- 

 trating them. He has also found on the inside of freshly removed hides, 

 which carried larvae in the first or cutaneous stage, small gnawed spots 

 which he believes to have been made by these larvae. He says also : 



The eai'liest grub holes that I have been able to find are very uniform in size, cor- 

 responding with the caliber of the grubs contained in them, and had no appearance 

 of the sac which forms later. The walls were rough, as if gnawed, and the hole was 

 cylindrical to near the epidermis, when it suddenly contracted. Now the freshness 

 of the wound and the absence of inflammatory action is a very good index of the 

 lateness of the wound, for, when a wound is exjjosed to the air, germs are sure to 

 enter, a sac grows and secretes pus. Were the wound of a more remote date it 

 would bo quite of another character, as every pathologist will admit. 



Upon this theory Dr. Curtice explains the " lick " as nothing more 

 than an cftusion of serum into the connective tissue cau.sed by the 

 inflamnnition induced by the wandering of the young grubs, and it 

 appears also in the walls of the esophagus just before the disappear- 

 ance of the grubs therefrom. These licks disappear from beneath tlie 

 hide when the grubs become stationary and the '' sacs " are well formed. 

 On reaching a suitable point in the back the warbles are supposed to 

 bore through the skin, caudal end first; this end being jH'ovided in 

 this stage with numerous rows of short stout spines (Figs. 48<i and 49c). 

 24164— No. 9 2 



