i8 Records of the Indian Museum. [Vol. X, 



The erection of what the author evidently intends as super-genera 

 is to be deprecated, as is, in fact, any system that introduces a 

 multiplicity of divisions. 



Comparative Examination of Structural Values. 



General. — Most families of the diptera, whilst quite well 

 circumscribed and distinct in themselves, exhibit fairly wide 

 diversity in several characters, whilst those parts of the body that 

 vary considerably in one family may be tolerably constant in 

 adjacent families or variable to a very much less extent, this 

 being exclusive of families with but a single genus each. For 

 instance, whilst the shape of the body and form of the antennae 

 in Syrphidae exhibit considerable variety (Baccha, Syrphus, 

 Eristalis, Microdon, Ceria), the venation is strikingly uniform; 

 whereas in the Tipulidae, the reverse is the case, the shape of 

 the body throughout the family being markedly uniform, whilst 

 the venation shows a large number of modifications. Other in- 

 stances could be cited, well known to dipterologists. 



It will now be my endeavour to compare the variation (or 

 otherwise) of the organs in Culicidae usually treated of, with the 

 variation of the same organs, speaking broadly, in other families 

 of diptera. 



The Proboscis. — The proboscis throughout the diptera is 

 exceptionally variable, ranging from the enormously prolonged, 

 conspicuous organ in Pangonia, Rhaphiomidas, Bomhylius , Nemes- 

 trina and other genera ; its lesser but still conspicuous and elongate 

 nature in Geranomyia, Empis, etc. to the very restricted forms in 

 many families: also from its long horny form in Stomoxys and 

 Drymeia to its soft prehensile nature in most Muscidae and 

 Acalyptrata; and again to its vestigial form in such species as 

 apparently take no nourishment in the adult state. 



In both comparative size and structure the proboscis varies 

 widely throughout the order, but usually not much within the 

 genus, and its range of variability is much greater in many families 

 than in the Culicidae. 



So far as structure goes, the proboscis is consistently uniform 

 throughout the subfamily Culicinae, whilst in the only other sub- 

 family {Corethrinae) the mouth is not formed for piercing. The 

 length varies in relation to the body, and this organ ma}'' be thin 

 throughout, swollen apically into a more or less elongated club, or 

 it may be foreshortened and thickened throughout. The modifica- 

 tions are not striking, and occur chiefly in the genera relegated by 

 Theobald to his Uranotaeninae and amongst those referred to the 

 Sabethini. 



The mere comparative length, unless very striking and consis- 

 tent, is not of generic value, as has been shown by its wide range 

 in Pangonia, Bombylius , Empis, etc. 



The Palpi. — Throughout the order, the palpi exhibit great 

 diversity, but usually conform to one of two forms, the elongate, 



