274 TIPULlDjE. 



the tip of the tibia.* In many genera they are easily seen. 

 The tarsi are always elongate, often being much longer than 

 the tibiae ; the ungues are sometimes smooth, sometimes with 

 teeth on the underside ; the empodia are often distinct, sometimes 

 absent, but pulvilli are wanting, except in PTYCHOPTERiN-E.t 



WINGS, j The costa is continued right round the edge of the 

 wing and not terminated suddenly in the neighbourhood of the 

 wing-tip as in some families of NEMATOCERA (Mycetophilidai, Chiro- 

 nomidce, etc.). The auxiliary vein (or subcostal) is of much greater 

 length than usual, nearly always reaching the middle of the wing 

 and often extending beyond three-fourths of the wing's length. 

 It turns down into the 1st longitudinal vein in the subfamily 

 TIPULIK-S, and up into the costa in the PTYCHOPTEIUX.E and 

 LmjfOBiixjE. In rare cases it is merged with the 1st longitudinal 

 (Antocfia, Toxorhina). The 1st longitudinal is invariably longer 

 than the auxiliary, except, of course, when fused with that vein, 

 in which cases the joint vein is termed the 1st longitudinal ; as a 

 rule it ends in the distal third of the wing. The 2nd longitudinal 

 originates from about the middle of the 1st, which is also 

 generally at or near the middle of the wing; it is nearly 

 always forked, the upper branch often being so oblique or per- 

 pendicular as to appear like a cross- vein. Barely the 2nd vein 

 is absent (Toxorhina). The 3rd longitudinal is always simple, except 

 in PiYCHOPTERnrJE, and very rarely absent (Paramongoma spp.). 

 The 4th longitudinal is invariably forked and at least one of the 

 bi-auches (more frequently the anterior one) forked again. The 

 4th vein begins at the base of the wing and invariably encloses 

 the discal cell, when such cell is present, as is normally the case. 

 The 5th, 6th, and 7th longitudinal veins normally present, generally 

 straight or slightly curved, the 5th usually bent somewhat down- 

 wards at the point where it meets the posterior cross-vein. In the 

 PTYCHOPTERIXJE the 6th vein is absent but the 7th is present. 

 The humeral cross-vein is always present ; the subcostal cross- 

 vein generally present in LIMNOBIIN.E, placed at various points 



* In many cases I have been unable to perceive these structures at all in 

 species belonging undeniably to genera theoretically supposed to possess them. 

 Osten Sacken, who was a great believer in their systematic importance, noted 

 that they were often very small and difficult to recognise ; but it seems to me 

 that they are more often absent than is generally supposed, and consequently 

 their biological importance is less than has usually been accorded them. 



t Too much importance should not be attached to minor differences, such 

 as the comparative size, toothed nature or otherwise, and so on, of the ungues 

 (claws) ; presence or absence of empodia, etc. When Theobald's first volume 

 on the CCLICID^E of the world was published, great stress was laid on very 

 microscopic differences in the shape and size of the different pairs of claws, 

 and in my " Catalogue of Oriental Culicidae " the great value attached to these 

 structures was questioned. In subsequent volumes of Theobald's work it was 

 admitted that they did not possess the value at first accorded them. 



\ As a Tipulid genus (Limnophila) was selected for the explanation of the 

 terminology of the venation in Diptera (p. 8), that portion of this work may be 

 studied in conjunction with the present description. 



