436 Osten Sachen: on tlie characiers of the tJiree divisions of 



lias little erect hairs in the middle of the joints of tlie flagellum that 

 iiiay be considered as „sensitive hairs". Aniong the Cecidomyiae 

 such liairs are wanfing in Äsphondylia\ among the T'rpulidae in 

 Pludacrocera. It is also worthy of noticc that the Tipulae from 

 New-ZeaUuid ^Ylüch I have seen, as well as several species from the 

 sonthern end of South-America (Chili, Argentine) which I know either 

 by sight, or from descriptions, have no verticillate hairs. Compare 

 in Macquart D. E. I, 1, p. 55 — 5(5 the descriptions of Tip. midicornis, 

 trimacidata, rt(fostigmosa, all of which speak of the antennae as 

 bare (nues); compare also the antenna of 21p. trimacidata figured 

 in Gay's Chili, Dipt. Tab. I, f. 2a. A specimen of Tip. decoraia 

 Phil., with similar antennae, I have before me. Such Tipulae may 

 perhaps represent one of those archaic types which occur so frequently 

 in these faunae. 



The sensitive hairs of the Nemocera vera are usually inserted 

 on a swelling at the base of the corresponding joints of the antennae. 

 Hence the tendency to the moniliform structure which characterizes 

 the antennae of this division. The greater the development which 

 these hairs reach, the greater the swelling, It is at its maximum in 

 the moniliform antennae of Cecidomyiae; at its minimum in the 

 Mycetophilidae, which have neither verticillate hairs, nor swelling. 

 The chilian Tipida decorata which I have before me, and which, 

 as I Said above, has no verticillate hairs, has cylindrical joints of the 

 antennae, without the usual swelling at the base. On the contrary, 

 in the exceptional Platyura from New-Zealand, which has short, in- 

 cipient „sensitive hairs", a slight swelling of the joints is also per- 

 ceptible. 



It will belong to a future micro-anatomist to investigate the struc- 

 tural and fnnctional dilferences that exist between the different forms 

 of bristles, hairs, pile, pubescence, down, and tomentum which occur 

 on the different parts of the body of Diptera: on the antennal joints, 

 the antennal arista, on different parts of head and face (mystax; 

 frontal, vertical and orbital bristles), on the edges of the tegulae, on 

 legs and wings (surface, costa, veins etc.). The functions of most of 

 these hairs are merely mechanical, as protective coverings, or tools. 

 for brushing, gathering, scraping or digging; but it is evident that 

 some of them are organs of sense. There is not the slightest doubt 

 that the peculiar, delicate, mostly erect and elastic hairs, .arranged 

 in regulär whorls on the antennal joints of the Nemocera vera be- 

 long to the sensitive order of hairs, and, as they are much more 

 developed in the male than in the female, that they have some part 

 to play in the bringing together of the sexes. They are peculiar to 



