772 



THE DIPTERA 



clature, which will be more fully explained under the heading Culicidss, but 

 which may here be compared with the typical arrangement of Comstock and- 

 Needham, from which it differs mainly by the form of coalescence called 

 ' inward,' which means that two veins have coalesced from the tip towards 

 the base of the wing. 



Dipteral Names. 



Costa. 

 Subcosta. 



First Longitudinal. 

 Second Longitudinal. 



Third Longitudinal. 



Fourth Longitudinal. 



Fifth Longitudinal. 



Sixth Longitudinal. 

 Seventh Longitudinal. 



The above table shows the two ordinary systems of nomenclature for the 

 v.'ing- veins of the Diptera at present in use. The terms in the right-hand 

 column are older than the other series, and are generally employed by English 

 writers. In addition to the longitudinal veins there are several transverse 

 veins, viz.:— 



1. The Flumeral from the Costa to Subcosta. 



2. The Radio-medial or anterior from the Radius to the Media. 



3. The distal Medio-cubital or posterior fromx the Media to the Cubitus. 

 z| . The proximal Medio-cubital or anterior Basal. 



5. The Cubito-anal or posterior Basal. 



The wing shows a costal cell, generally subdivided by the humeral vein, a 

 subcostal, a marginal, a variable number of submarginal, a posterior, and an 

 anal cell. The second anal vein is often wanting, and represented by merely 

 an incrassation. In addition there are generally an anterior or radial, a 

 posterior medial, and an anal or cubital basal cell. In the Culicidae the first 

 submarginal and the second posterior cells are often called the fork cells. In 

 the hrst posterior cell it is important to note whether it is closed, and does not 

 reach the margin of the wing owing to the junction of the media with the 

 radius, or open, or partially open, and does reach the margin of the wing. A 

 distal cell in the middle of the wing is present in some genera. It is bounded 

 either by the media or by that vein and the cubitus. 



The legs possess the usual number of segments, but with regard to the 

 nomenclature of these segments there is a certain amount of confusion. The 

 fifth tarsal segment carries two claws and usually two pulvilli or pads, while 

 between them lies the empodium in the form of a bristle or third pad, which 

 may be looked upon as a sixth tarsal or claw segment. 



Abdomen. — This has usually nine segments, which m.ay be reduced by the 

 fusion of segments, especially in connection with the male and female genera- 

 tive organs. The genitalia, especially the male, are of importance in classifica- 

 tion, and will be mentioned in detail under the heading Culicidae. 



The body is adorned by scales and hairs. The former have been made use 

 ot by Theobald to classify the Culicidae, while the latter may be strongly 

 developed in places, and have been used in flies as a help in classification, 

 and are of the utmost importance in fleas. 



Flies are usually modest in colour, being often yellowish, brownish, or 



Typical Names. 



Costa 



Subcosta 

 Radius i 



Radius 2 1 ^ , , 

 -o > Coalesced . . 



Radius 3 j 



Radius 4 



Radius 5 j ^oaiescea . . 

 Media i "\ 



Media 2 I Coalesced more or) 

 Media 3 T less . . , . / 

 Media 4 j 

 Cubitus 1 

 Cubitus 2 j 

 Anal I ) 

 Anal 2 / 

 Anal 3 - . 



