1921] Huckett: Ovipositor of Anthomyian Genera 293 
The segments of the ovipositor are alternated by a well 
developed membrane known as the intersegments. The func- 
tion of the latter is to provide a membranous sheath for the 
folding up of the segments and to increase the range of the 
ovipositor when necessary. The intersegments may be smooth, 
without vestiture, as in Pegomyia affinis Stein, Hylemyia lipsia 
Wlk., and Chortophila longula Fallen, or covered with minute 
spines, partially or wholly. These recurrent spinules are some- 
times arranged in transverse striz, or as broad, imbricated 
spinules in no definite order, as in Chortophila parva R-D. 
caerulescens Strobl. and cinerella Fall. These spinules, although 
they appear to be limited to definite areas, yet frequently are 
to be found on adjacent membranes and sclerites, there being 
no definite demarkation. The annulations of the segments 
can, however, be always determined. 
Intersegment nine is considerably reduced in size and dis- 
similar in form to the three preceding membranes. It functions 
as an attachment for the modified ninth segment (suranal and 
subanal plates) to the caudal margin of the eighth segment, as 
well as serving in a telescopic manner for the inclusion of the 
ninth segment when the ovipositor is retracted. Further the 
ligaments of the cerci are associated with the ninth inter- 
segment. 
The segments represent chitinized areas that are unstable 
both in delineation and degree of chitinization. Though 
functioning primarily as a strengthening device for the rigidity 
of the ovipositor, it undergoes changes in structure to provide 
elasticity and collapsability. Thus the dorsal plate (tergum) is 
frequently composed of two lateral pieces that are more heavily 
chitinized caudad than cephalad, and whose margins blend 
imperceptably into a mid-dorsal membranous area known 
as the discal area, or into the lateral conjunctive, ventrad. 
Degrees of chitinization, varying from a complete dorsal 
encasement, as in the abdomen proper, to vestiges of chitinous 
thickenings in the membrane, have been found in a series of the 
same species. This is thought to depend upon the age of the 
adult, degree of development, condition of pupation, etc., so 
that it is deemed inadvisable to put much credence in its 
taxonomic value.* The caudal margin of each tergum is 
* The peculiar outline of the chitinous thickenings on segment eight in Chor- 
tophila brassice Bche, and antiqua Meig, have been so constant in the specimens 
under examination that it has been thought fit to make an exception of this case 
and to include this character in the key. 
