EGG OF BOT-FLY, OE (ESTRUS. 103 



STING OF WASP AND BEE. 



The weapon of defence given to these insects consists of 

 a barbed dart and a bag of subtle poison. The dart itself 

 is composed of two blades, with serrated edges, enclosed in 

 a sheath, and attached by strong muscles to the side of the 

 abdomen ; near the slit by which it protrudes are two hairy 

 appendages, which act as brushes and keep it clean, and at 

 a short distance within a slender canal leads to the bag of 

 poison, which, pressed by the muscles in the act of stinging, 

 gives out the acrid drop which irritates the wound to such 

 painful swelling. 



STING OF GNAT. 



See Head of Gnat. 



STING OF TABANUS. 



See Head of Tabanus. 



EGG OF BOT-FLY, OR (ESTRUS. 



There is not a more curious and interesting object than 

 this. Those little spots which cover the fore-legs of horses 

 from the latter end of July to the end of September, are 

 eggs like this, deposited by a fly called (Estrus, or Gad-fly. 

 The longest period of this fly's life is passed in the intes- 

 tines of the horse, and all the Winter every horse exposed 

 by field work or pasture feeding to the attacks of the 

 (Estrus is full of the larvae which hatch from this egg. 



The fly itself appears only in July, and is properly called 

 Gasterophilus, or Stomach-lover. A tawny body very 

 hairy, wings dingy white, and with a transverse gray band ; 

 without any proboscis, for it lives but a very short time 

 only to lay its eggs and die. The abdomen is bent inwards, 

 the female having a retractile tube consisting of four pieces, 

 and terminating in five points, within which she holds the 

 egg, and hovers over the horse, lightly darting at him, and 

 depositing each egg upon a hair. This egg is firmly 



