64 FIRST REPORT ON ECONOMIC BIOLOGY. 



the stomach, where they were hatched ; but on more minute search I 

 do not find this to be the case, or at least only by accident ; for when 

 they have remained on the hairs for four or five days they become ripe, 

 after which the slightest application of warmth and moisture is 

 sufficient to bring forth in an instant the latent larva. At this time, 

 if the tongue of the horse touches the egg, its operculum is thrown 

 open, and a small active worm is produced, which readily adheres to 

 the moist surface of the tongue, and is from thence conveyed with 

 the food to the stomach. If the egg itself be taken up by accident, 

 it may pass on to the intestinal canal before it hatches ; in which case 

 its existence to the full growth is more precarious and certainly not so 

 agreeable, as it is exposed to the bitterness of the bile. 



I have often, with a pair of scissors, clipped off some hairs with 

 the eggs on them from the horse, and on placing them in the hand, 

 moistened with saliva, they have hatched in a few seconds. At other 

 times, when not perfectly ripe, the larva would not appear, though 

 held in the hand, under the same circumstances, for several hours ; 

 a sufficient proof that the eggs themselves are not conveyed to the 

 stomach. . . . The eggs, in the first place, when ripe, often hatch 

 themselves, and the larva, without a nidus, crawls about till it dies ; 

 others are washed off by water, or are hatched by the sun and 

 moisture, thus applied together." 



Other writers state that the eggs hatch after a time, and the 

 horse, feeling the irritation of the larvae creeping over the skin, licks 

 itself and thus conveys them to the mouth. 



Finally, Osborn 1 has recorded a series of most interesting experi- 

 ments. He writes: " Eggs collected from a horse while flies \\crc 

 depositing, and therefore probably not long laid, were opened at 

 different times by rubbing them with a moistened finger, simulating 

 as nearly as possible to the action of the tongue in licking the body. 

 While the larvae appeared to be fully formed during the first three 

 or four days after deposition, the eggs hatched with difficulty and the 

 larvae seemed inactive, and all larvae that were freed in this manner 

 up to the tenth day were hatched with difficulty, though the larvae at 

 the end of this time was becoming fairly active. 



Four weeks after hatching the eggs opened with the slightest 

 touch of a wet finger, and the larvae adhering to the finger were very 



1 Op. cit. 



