60 H. C. HUCKETT 



Calythea albicinda and Anihomyia pluvialis. The spinules may differ 

 in character and arrangement. Typically they are minute recurrent 

 spinules, scattered densely on the membrane. Occasionally they are 

 arranged regularly in transverse striae, as in Egle muscaria. In some species 

 (as, for example, Paregle radicum, P. cinerella, Anthomyiella pratincola, 

 Hylemyia lasciva, and Pegomyia luteola), the spinules appear scale-like, 

 resembling small, flattened, triangular plates. In Pegomyia connexa, 

 intersegment 8 is armed with stout hooks as well as with spinules. 



In the genera Hammomyia, Hydrophoria, and Neohylemyia, the dorsal 

 and ventral regions are developed unequally, so that there is a considerable 

 buckling or overlapping of the segments with the intersegments. This 

 causes the ovipositor, when extended, to form a sharp curve, or arc, in a 

 downward direction. 



The cerci 



The cerci form the paired anal appendages which arise laterad of the 

 anal opening. (The anus is assumed to have come to lie within the tenth 

 segment, due to the atrophy of the eleventh.) In appearance the cerci 

 resemble palpus-like or club-shaped appendages. In reality they are 

 hollow conical or saucer-shaped plates, the inner surface of which is lined 

 with a delicate membrane. The proximal region has become considerably 

 attenuated, so that in certain species it appears like a petiole, or stem, 

 of attachment. 



The armature of the cerci is typically composed of setae and hairs. In 

 addition, minute sense organs with trigger-like papillae are to be found 

 near the apex of each cercus. In the genera Hammomyia, Hydrophoria, 

 and Neohylemyia, stout curved spines are present on the cerci, besides 

 the normal setae. 



The integument of the cerci, like that of the segments and the inter- 

 segments, may be spinulose, as in Hammomyia spp., Neohylemyia spp., 

 and Hylemyia variata; or it may be smooth, as in Pegomyia calyptrata, 

 P. hyoscyami, and P. ruUceps. 



