A CONTRIBUTION TO THE KNOWLEDGE OF BOT-FLIES. 



97 



experience would corroborate this statement, it can be definitely stated, as the results 

 on Table I show, that the eggs of G. nasalis hatch quite freely without extraneous 

 aid. For those of G. haemorrhoidalis no definite assertion can be made, as the number 

 of eggs at our disposal was rather small. However, in one case, out of 14 eggs of 

 this species, 8 hatched independently in a dry vial. 



Table I. — Experimental Hatching of Eggs of Bot-flies in Vials, unaided. 



Species. 



Number 

 of un- 



hatched 

 eggs. 



Date 

 when 

 collec- 

 ted. 



Number 

 of eggs 

 hatched. 



Date of 



hatching 



of last 



egg- 



Remarks. 



G. intestinalis 



7 



July 28 







— 



3 alive Aug. 28, 4 dead. 





250 



Aug. 5 



1 



Aug. 16 



Larvae in eggs alive Aug. 16 





206 



Aug. 20 



4 



Sept. 6 



Remainder dead. 





13 



Aug. 26 







— 



All dead in September. 





12 



Aug. 27 







— 



Alive Sept. 4, died later. 





130 



Aug. 27 



6 



Sept. 21 



4 hatched only partly. 



G. nasalis 



40 



July 11 



32 



July 23 



Remainder died. 





69* 



July 11 



43 



July 23 



s> »> 





29 



July 18 



22 



July 28 



>> ,j 





8 



Aug. 3 







— 



Aug. 29, all dead. 





79f 



Aug. 5 



28 



Aug. 20 



Remainder died. 



G. liaemorrhoidalis . . 



14 



July 20 



8 



July 24 



1 damaged, remainder died. 



* The glass vial containing these eggs was kept slightly moist by means of a wetted 

 piece of blotting-paper inserted between the cork and the walls of the vial. 



f Includes some eggs which had hatched before they were collected from the horse, 

 the number of which was not determined. 



In the case of G. intestinalis, the experiments were continued until the end of 

 September, and the eggs were frequently examined, at least three times a week. 

 A large number of eggs in each batch were dissected after the date on which the last 

 larva was observed to emerge. In most cases the larvae inside were alive and, when 

 liberated, were quite active. From the results, it may be apparently deduced that 

 the eggs of G. intestinalis normally require assistance in hatching in the shape of 

 moisture and friction, and that only a very small percentage (l - 7) contrive to hatch 

 unaided. In support of this fact, it was found in frequent tests that hatching is 

 readily promoted when the eggs are moistened and subjected to pressure by passing 

 the blunt edge of a scalpel over them. In some, only slight pressure is required, 

 just sufficient indeed, to cause the operculum to spring from its attachment with the 



