2 BRITISH FLIES 



Nobody has studied these higher divisions of the Dipteea more 

 thoroughly than Osten Sacken, and nobody is more competent to 

 diagnose their distinctions ; consequently, I cannot do better than quote 

 his formulffi as given in the Berliner Entomologische Zeitschrift, vol. xxxvii., 

 p. 422 (1892). 



" I. Palpi generally four-, or five-jointed,^ pendulous, and more or less 

 " filiform ; antenuEe many-jointed (more than six-jointed), generally fili- 

 " form (seldom pectinate), with the majority of the joints of the flagellum 

 " of a homologous structure." "' — " Nemoccra, Latreille." 



"II. Palpi one or two-jointed, porrect (not pendulous), the second 

 " joint more or less clavate, larger than the first, which in this case 

 " appears like a handle to the second; the joints of the antennal flagellum, 

 " with rare exceptions, not homologous."-"' 



" Orthorrhapha Braehycera and Cy dor) kapha Athericera." 



As additional characters for the Nemoceka Osten Sacken later on added, 

 " No macrochsetye ; no tegul8e,(*) but the antitegula (*) is almost always dis- 

 " tinct; the alula and the axillary excision are but little developed or 

 " entirely absent. No discal cell (exceptions: Tipulvla'., Rhyphidca). Larvse 

 " with a distinct head in the shape of a horny shell, mandibles with a 

 " lateral mobility, opposed to each other like pincers ; round-headed 

 " larvffi." 



1 " It is very probable that the palpi, in most cases, are only apparently five-jointed, the basal joint repre- 

 " senting the maxilla, or a portion of it." 



2 " In this paper I have used the word homologous in its ordinary sense, as ' having the same relative 

 " position, proportion, value, or structure' (Webster's Dictionary), and not in the narrower sense, used by 

 " zoologists : for instance that the hand of man and the fore-foot of a horse are homologous. Observe that 

 " the joints of a flagellum, for being pectinate, do not cease to be homologous." 



:' " ' Joints of the flagellum not homologous.' I purposely use this, merely negative, definition, in order to 

 '' leave room for the endless variety in shape of the third joint of the antennii- of the Bnichycera ." 



(') Tegula .ind antitegula = my thoracal and alar squama. 



