48 REPORTS OF OBSERVATIONS AND EXPERIMENTS. 



applied. Again, on October 26, two or three eggs were used, each of 

 which gave off the cap very readily, but in none of them did I find any 

 active larvae, although one of the larvae seemed to be fresli and showed 

 very feeble movement. October 27 one egg hatched as before and gave 

 a larva which appeared inactive. Another, hatched at the same time, 

 appeared inactive at first, but, upon the addition of a drop of saliva, 

 showed at first a slight amount of movement at the head end, being 

 most apparent iD the hooks and later quite decided contractions 

 appeared in the forward part of the body, the larva becoming in a short 

 time sufficiently active so that there would seem to be no difficulty in 

 its securing proper conditions for development and ability to attach 

 itself to the mucous membrane of the alimentary canal had it been set 

 free upon the horse's tongue. 



October 28 seven eggs were opened by means of moisture and rub- 

 bing as heretofore, and these all proved to be inactive, three of them 

 thoroughly plump, but not recovering when placed in a drop of mois- 

 ture, while the others were shriveled and two of them adhered to the 

 shell. 



I also found among the remaining eggs one from which the larva was 

 partially free, the cap of the eggshell adhering to the front end of the 

 larva and the larvae wriggling about actively, the tail portion only being 

 connected with the shell. 



One or two other eggs had been noticed from which -the caps were 

 removed, and these had probably hatched by their own efforts. This 

 would seem to show that it is possible, although not a normal habit, 

 for the embryos to push the egg cap off and escape without assistance. 



Summing up the results of these observations, which were riot as 

 complete as might be desired, it seems that we may, with considerable 

 certainty, reach the following conclusions. Some difference, due to the 

 changing conditions of moisture, may be possible under field condi- 

 tions, the conclusions being strictly applicable only to the conditions 

 under which these eggs were kept : 



(1) That the eggs of the horse bot-fly do not hatch, except by the 

 assistance of the horse's tongue. 



(2) That hatching does not ordinarily occur within ten or twelve days 

 and possibly longer, or, if during this period, only on very continuous 

 and active licking by the horse. 



(3) That the hatching of the larvae takes place most readily during 

 the third to fifth week after deposition. 



(4) That the majority of the larvae lose their vitality after thirty-five 

 to forty days. 



(5) That larvae may retain their vitality and show great activity upon 

 hatching as late as thirty -nine days after the eggs were deposited. 



(6) That it is possible, though not normal, for eggs to hatch without 

 moisture or friction. 



