5S H. C. HUCKETT 



are characteristic of such closely allied species as Hylemyia inornata, H. 

 setigera, H. piloseta, H. marginata, and H. marginella. The inner margin 

 of each process may possess a charactersitic series or tuft of hairs or setulae, 

 as in Anthomyia yluvialis, Egle parva, Pegomyia juvenilis, P. luteola, P. 

 rubivora, Hylemyia hetarum, and Hydrophoria uniformis ; or, again, these 

 surfaces may be devoid of such hairs, as in Paregle cinerella, Pegomyia 

 bicolor Hylemyia alcathoe, H. dlicrura, and H. trichodadyla. 



THE OVIPOSITOR 



The ovipositor represents the modified terminal segments, 6 + 7, 8, 9, 

 and 10, of the abdomen f Plate I, j). Such designation of the segments is 

 in accordance with the following assumptions: (1) that the abdomen proper 

 (preabdomen) consists of segments 1 to 5, the first tergum having fused 

 with the second; (2) that the occurrence of two pairs of spiracles on a single 

 apparent segment indicates the identity of two fused segments; and (3j that 

 the appendages of the ultimate segment represent the cerci. 



The ovipositor may be divided arbitrarily into three component parts — • 

 the segments, the intersegments, and the cerci. 



The segments 



Each segment is composed of the reduced tergum and sternimi of the 

 abdomen, together with the lateral conjunctivae. The tergum and the 

 sternum of segment 10 are modified to form the upper and lower lamellae 

 at the anal opening, that is, the suranal and subanal plates. The degrees 

 of chitinization of the plates vary considerably within a species and between 

 species. Typically the tergum is divided along the mid-dorsal line into 

 two lateral, more hea'vily .chitinized tergites, which tend to fuse along the 

 caudal margin. The sternum is represented by a single median plate 

 except in segment 9, where it is typically divided into two .sternites (except 

 in Pegomyia hyoscyami) . The caudolateral angles of the terga of segment 

 6+7 and segment 8 may become accentuated by a thinning of the chitin 

 across those regions, so that chitinous areas become isolated and form 

 accessory pieces, as in Pegomyia unicolor, P. calyptrata, P. fuscofasciata, 

 P. ii^nthemi, P. connexa, Paregle radicum, Hylemyia lasciva, Neofiylem^yia 

 mallochii, and other species. 



The spiracles of the ovipositor are reduced to two pairs which are found 

 tj^pically in the vicinity of the lateral margins of tergum 6 + 7. Frequently 

 they are found close to each other at the caudolateral angles of the tergum, 

 or in association "^ath the accessor^' pieces, as, for example, in Pegomyia 

 luteola, P. fuscofasciata, Paregle radicum, and Hylemyia lasciva. Occa- 

 sionally the caudal pair of spiracles may appear on the membrane of inter- 

 segment 7, as in Pegomyia hyoscyami and Hammomyia paludis. 



The armature of the segments is typically represented by bristles, spines, 

 hairs, and setulae, either in a single or a scattered series or as a dense 



