BY JOHN L. FROGGATT. 663 



outer slits, and somewhat less strongly between the middle and 

 inner slits; in the latter case, this projection usually forms a 

 hollow above the space in the upper end of the " intermediate 

 structure." Slits fairly close together, and running practically 

 the whole length of the plate. Outer and inner slits fairly 

 straight througliout their whole lengths. The lower half of the 

 middle slit is fairly straight, from which point it bends slightly 

 inwards. " Blister-structure " usually situated just above the 

 point of curvature. " Intermediate structure " always present 

 between the middle and inner slits, and well developed. In a 

 few cases, a similar structure has been noticed between the outer 

 and middle slits, but then the " blister-structure" on the middle 

 slit is absent. " Blister-structure" well developed on the slits. 

 The "sun-ray" effect is particularly well marked on the " blister- 

 structures" and on the space in the top of the "'intermediate 

 structure." 



Pycnosoma rufifacies. (Plate Ixx., figs.5, 5a). 



Anterior Spiracles. — Cap differentiated into two parts. Tu- 

 bules long. 



Posterior Spiracles. — Band very strong, often differentiated 

 into two parts, the chitinous material being thinner on the outer 

 portion. It would seem that, when the maggots are young, the 

 differentiation in the band is most marked, but as development 

 is carried on, this differentiation decreases until the two parts 

 become either fused or the outer becomes the thicker and stronger. 

 There is, of course, no space between these two parts in the band. 

 The band is broken at the base, leaving the space open and in- 

 completely surrounded. The band is always much thicker at 

 the base. The inner edge of the band projects downwards 

 slightly between the middle and inner slits, and less markedly 

 between the middle and outer slits. The outer margin of the 

 band is regular in outline. The slits run the full length of the 

 plate, abutting on the inner edge of the band at the top and 

 bottom of the spiracular plate. The outer slit, in shape, is fairly 

 straight on the inner side, the outer side being slightly convex, 

 following the outline of the inner margin of tlie band. The lower 

 part of the middle slit is fairly straight, and close against the 



