47''^ TIPULTD.E. 



constant differences in venation. Parrnnongoma need not here be 

 discussed, since the only Oriental species is the P. alhitarsis of 

 Doleschall, described many years ago from Java and apparently 

 never recognised since. 



The other two may be easily separated as follows : — 



Four posterior cells; * discal cell present Alunr/oDia, Westw. 



Three posterior cells ; discal cell absent Mon</vmwides, Brun. 



Mongoma (sensu Into) is highly interesting as presenting one of 

 the most conspicuous variations from the normal type of venation 

 in this family. Previous to describing the genus Prof. Westwood 

 wrote to Osten 8acken for his opinion, and the latter's reply is 

 indicative of its abnormality in his words: "The systematic posi- 

 tion of this species {M. fragiUima) is very puzzling . . . ." He 

 pointed out that the apparent resemblance between its venation 

 and that of Paratropeza, Sch.,t Avas only superficial and that it was 

 certainly a new genus. 



Westwood's figure of the original species, M. fragUlima. from 

 Central Africa, is excellent, and clearly portrays the distinctive 

 features of the genus ; the long auxiliary vein ending only just 

 before the tip of the 1st longitudinal ; the wide forking of the 

 2iid vein, which, with the marginal vein, gives a first impression 

 of the marginal cell being divided by two cross-veins into three 

 portions ; the merging of the 'Srd longitudinal vein in the 4th,t at 

 the upper basal corner of the discal cell, thereby causing the 

 absence of the anterior cross-vein ; the abrupt curve downwards of 

 the end of the oth vein, closing, in most cases (speaking sensu 

 lata), the anal cell ; the shortening of tlie two basal cells and the 

 very short 7th vein, — all characteristic features of this singular 

 genus.§ 



Even Osten Sacken, than whom no better authority on Tipulid.e 



* As regards the names of the posterior cells, it must be remembered that, 

 as the anterior cross-vein is wanting, the Jirsf posterior cell is absent, and that 

 the u])iierniost of tlie posterior cells, whether four or only three be present, is, 

 strictly speaiiing, tlie second and not the first. This view is coniinued by 

 Willistoii. 



■!• For description of I'aratropc::a see Verb, zool.-hcjt. Ges. Wieu, xvi, p. 932 

 (1866). 



\ This view is in accord with Williston's opinion (Tr. Ent. Soc. 1896, 

 p. 292), but I only recently saw this author's paper, long after I had studied 

 the question personally. 



§ Of course, if the short vein joining the 2nd vein with the discal cell (or 

 the corresjwnding part of the 4th vein when tlie discal cell is absent) be con- 

 sidered the anterior cross-vein instead of the Srd longitudinal vein, it follows 

 that there would be only one subinarginal cell in any of the three genera 

 concerned, and the cell exterior to the anterior cross-vein will become the 

 1st posterior cell. This would give Moiu/oitta iive posterior cells, and Mo)igo- 

 mloides and Paraiiiongoma four posterior cells each. In support of this 

 suggestion it may be urged that the ord vein is not known elsewhere to ter- 

 minate in the interior of the wing. Personally I know of no case where it 

 does so. but it must be remembered that excessive almormalities are nut rare 



