and of several Brachyccrous families in Dipicra. 287 



marked, and relatively large ; this condition is well seen 

 in some Mycetophilida. A somewhat similar structure is 

 found in some Dolichopodidte, that in Porphyrons gravipes, 

 Wlk., being a good example. 



In P. incrassata, P. rujipes and T. aterrima and a number 

 of other species this is so far modified that the plate has 

 gone, but the eyes are bordered by chitinous bands, and in 

 each junction of the bands is a socketed hair, very similar 

 if not identical in structure with the hairs found in the 

 Nematocera or Brachycera. The pubescence found on 

 the eyes in the Muscida^ is of a different type, being 

 transparent and weak, and not tapering, just the opposite 

 being found in the Nematocera, where each hair tapers 

 from a comparatively broad base to an exceedingly sharp 

 point, while in the Muscidaj the socket is so minute as 

 often to be scarcely visible, and the lenses are never 

 separated by bands. 



7. TJie structure of the hair and bristles. This is peculiar; 

 it is as if each single bristle were made up of a number of 

 fine hairs of various lengths, so that its point and edges 

 appear almost plumose, certainly serrated. The hairs are 

 numerous and strong, and so characteristic in appearance, 

 that it is easy to recognise them as either from a Phorid, 

 or as the apical bristles from the tibia3 of a Mycetophilid. 

 The Mycetophilidse are the only other family in which 

 this structure is found, and in them only on the tibiae. 

 It is figured in Becker's monograph already referred io, 

 but will require a magnification of 250 diameters to see 

 clearly on the actual insects. It is so characteristic, that 

 even were other similarities absent, I should consider it a 

 strong mark of relationship. 



8. The mouth 2^ arts are difficult to study owing to small- 

 ness of size, but can easily be seen to have but little 

 affinity with those of tlie Mycetophilidje, and indeed might 

 be thought to approximate (as they do in some characters) 

 to the Muscid form, yet as I shall show later, can only be 

 homologised by comparison with Nematocerous forms. 



Except in Gymnophora arcuata, Mg., and here I am not 

 quite certain owing to the imperfection of my preparation, 

 the armature of the species examined is different in the 

 sexes. Not in the manner found in Tahanus and Culcx, 

 where the males are without the mandibles, but in the 

 structure of the labrum and the aculeations or teeth on 

 the paraglossse; the labrum has in the females of many 



