68 CH^ETOTAXY. 



(intra-liumeral of Osten Sacken) absent. Notopleural (of 

 Girschner and Hough, post-humeral of Osten Sacken), 2. Prse- 

 sutural, I* Sup-a-alar, 1. Inira-alar, 1, situated just in front 

 of the post-alar callus, on a level with the second dorso-central.f 

 PoHt-alar, 3, the foremost somewhat smaller than the other two, 

 and placed directly above the alar frenum.J Dorso-central, 3, 

 two near together, close to the hind margin of the dorsum, and 

 one immediately in front of the suture ; the latter bristle may be 

 termed the pnesutural dorso-central.^ Inner dorso-central, \\ 1, 

 near the hind margin of the thorax. Scutellar, 2, one marginal 

 (near the basal angle), the other apical ; in certain specimens of 

 Glofisina fusca, Walk., and Gl. longipennis, Corti, there is a 

 second marginal bristle in front of the ordinary one, and also, in 



* Often small and difficult to distinguish in Gl. palpalis. 



t I follow Hough {h)c. cit. p. 180) in numbering the dorso-centrals 

 froni rear to front, except that, for reasons explained in the note below, I 

 term the comparatively large dorso-central bristle immediately in front of 

 the transverse suture tho prassutiiral dorso-central. 



X Cf. Osten Sacken, Trans. Ent. Soc. Lond. 1884, p. 504. 



§ In certain cases [e.g. individual specimens of Gl. moraitans and 

 Gl. longipalpi^) there are one or more small additional bristles (little larger 

 than the small bristle-like hairs clothing the general surface of the 

 dorsum, but nevertheless recognisable as bristles belonging to the dorso- 

 central series) between the second dorso-central and the suture. It is 

 therefore obviously impossible to give the dorso-central bristle in front of 

 the suture a numerical designation. 



N.B. — In Fig. 10 the extra dorso-central bristles, as well as certain 

 others which sometimes occur, are not shown, the object being to represent 

 so far as possible the normal chastotactic arrangement in the genus. 

 Aberrations in chffitotaxy noticeable in the material available for examina- 

 tion will be referred to under the individual species. 



II Cf. Mik, " Ueber Acrostichalborstchen {sctiilie acrostichalcs) " : Wien. 

 Ent. Z". xix. Jahrg. 1900, pp. 151-152.— Aspointed out by Mik {loc. cit. p. 152), 

 recent writers on Muscidie, such as Girschner and Stein (as also Hough), 

 following an original slip on the part of Osten Sacken {cf. Trans. Ent. 

 Soc. Lond. 1884, p. 509), have misapplied the term acrostichal in using it 

 for the i)inrr dorso-crntral series of bristles. The small acrostichal 

 bristles, however, cannot be interpreted as inner dorso-central bristles. 

 Mik adds : " The dorso-central bristles are always symmetrically 

 (bilaterally) arranged macrocluetas, whereas the little acrostichal bristles 

 (Acrusticliallor.'ifchcn) belong to the ordinary original covering of the 

 dorsum of the thorax and occur by no means seldom in a single row along 

 the sagittal line, or may form even more than two longitudinal rows. It 

 may also happen that little acrostichal bristles occur even when the two 

 rows of the inner dorso-central bristles are present. Whoever, for instance, 

 examines a Dolichopodid provided with little acrostichal bristles will at 

 once recognise that these little bristles have nothing to do with the 

 macrochsetee, but that they belong to the same category of covering 

 {Bcklcidung) as the tiny bristles that occur on the anterior portion of the 

 mesothorax, especially behind the humeral calli." 



I am indebted to Mr. J. E. Collin for directing my attention to Mik's 

 note, which otherwise I should have overlooked, as it is concealed among 

 the last instalment of the lamented author's " Diptcrologische MiscoUeu." 



