50 



THE INTERNAL STRUCTURE OF MUSCA DOMESTICA 



There is a single pair of accessory glands (ac.g.) which are 

 fairly long, and on nearing the vagina they become narrower to 

 form a slender duct which opens on the dorsal side of the vagina 

 immediately behind the ducts of the spermathecae. The accessory 

 glands are closely united with the fat-body. They probably 

 secrete the adhesive fluid which covers the eggs when they are 



sp. 



Fig. 21. Terminal region of tlie female reproductive organs, showing the accessory- 

 glands, etc. 



sac. Sacculus. vag. The muscular vagina which evaginates during copulation ; 



a pair of retractor muscles are shown. Other lettering as in fig. 20. 



laid, and causes them to adhere to each other and to the material 

 upon which they are deposited. Behind the accessory glands there 

 is a pair of thin-walled transparent vesicles (tasche dell' ovidutto of 

 Berlese), which I propose to name the accessory copulatory vesicles 

 (a.c.v.) on account of the part they take in ensuring firm coitus 

 with the male when copulating, during which process they expand 

 to a much greater extent. 



TJie ovipositor (fig. 22). 



The terminal abdominal segments of the female are much 

 reduced in size to form a tubular ovipositor, the chitinous sclerites 

 being reduced to form slender chitinous rods. When extended it 



