278 ~=Prof. L. C. Miall and Mr. T. H. Taylor on the 
14, 15) which pass to the inner face of the tube (7th 
segment). They enclose between them a median portion 
of the hemoceele, in which lies the 
special muscular portion of the uterus. 
It is difficult to say whether these 
oblique muscles effect a change in the 
shape of the external wall of the 7th 
segment or in that of the conical ex- 
tension. It is possible that they serve 
to protrude the ovipositor by setting 
up an increased blood-pressure in the 
last segments of the body. The 8th 
and 9th segments are specially modified 
to form the ovipositor. The dorsal and 
ventral surfaces of the 8th segment 
bear an elaborate arrangement of 
denticles (figs. 16, 17) which facilitate 
the operation of boring into the tissues 
of the holly-leaf during feeding and 
oviposition. The 9th and last segment 
bears at its posterior extremity a pair 
Rea of short valves. The thin intersegmental 
Ovipositor of fly, dorsal CUticle between the 8th and 9th seg- 
ToT tay Cote ana ee is much enlarged, and permits 
not shown, (x 120.) the 9th segment to be completely 
telescoped into the 8th (figs. 18, 19). 
ez 
Fic. 18. 
Posterior abdominal segments of female fly, diagrammatic. The ovipositor is 
extended. The left ovary alone is shown; one tubule is complete; 7, rectum; the 
rest of the lettering as in fig. 13. 
The hinder-part of the 8th can be folded back into the 
fore-part. When fully retracted, the ovipositor is enclosed 
