100 CONNECTICUT GEOL. AND NAT. HIST. SURVEY [Bull. 



TAXONOMY 



Wing Venation 



R. B. Frien!) 

 Connecticut Agricultural Experiment Station 



In view of the fact that the collaborators in the present work 

 have not used the same terminoloo:y in naming- tlie wing- veins, al- 

 though within any one family uniformity exists, it is necessary to 

 discuss the wing ' venation briefly in order to clarify a condition 

 which may be confusing to those not familiar with the classification 

 of Diptera. No attempt is made to evaluate the merits of any one 

 system, nor to arrive at any decision on the true homologies of veins, 

 either within the order or with the veins of other orders of insects. 

 It may be found, hoAvever, that the key to families gives a vein one 

 name while the classification of the family itself, by another author, 

 calls the vein something else. It will also be noticed that in one 

 family the veins receive names totally different from the names em- 

 ployed in describing another family, although the actual structure 

 of the wing in these two families is strikingly similar. The system 

 of termhiology an author uses is a personal matter, and it has not 

 been considered expedient to attempt to impose a uniform system on 

 all collaborators. Such an attempt would probably fail. The ac- 

 companying illustrations of the wings of several flies will, it is hoped, 

 be of some assistance in this matter as well as an aid in using the 

 key to families. 



The Comstock-Needham system is used in describing the wing 

 venation of most insects and is the best known terminology. It is 

 thoroughly discussed by Comstock (The Wings of Insects, 1918). 

 According to this author the wing venation of primitive Diptera 

 departs from the hypothetical primitive type of insect wing venation 

 only in the reduction of the number of veins by coalescence or atrophy. 

 Neither accessory nor intercalary veins are ever developed, and only 

 the principal cross veins are present. In the more specialized Diptera 

 adjacent veins have frequently coalesced. 



The marginal vein of the wing is the costa (C). It is usually 

 more conspicuous along the anterior margin of the wing. 



The subcosta (Sc) branches once in some primitive Diptera, as 

 in Protoplasa (Figure 15). It may end in the costa, a more common 

 condition, or in the radius, or the tip may be evanescent, or the entire 

 vein may be missing. 



The radius (R) retains all five branches in the Psychodidae and 

 in the Tanyderidae, as Protoplasa. In most forms the radial sector 

 (Rs) has less than the primitive number of four branches, the re- 

 duction even extending to the single-branched condition. In some 



