332 C. R. Osten Sacken: 



wheiiGver Rondan i meant to mention, or to describc, one of thc 

 pairs of squamae separately, the anterior pair or the posterior, or 

 to institute a comparison between tliem, he, like R.-D., used the terni 

 squamae, alvvays adding the word calyptrornm, to indicate that 

 calyptra meant the comp lex, the ensemble of the post-alar 

 membrane (abundant references to Rondani's terminology will, be 

 foiind in Note III). The insistence of Rondani in making this 

 distinction leaves no doubt about Ins Intention. I again repeat, that 

 neither calyptum nor calyptrnni have ever bcen used in the Sin- 

 gular, either by R.-D. or by Rondani; both used sqnama for it, 

 a term that, as I have shown in my article (p. 286), has been used, 

 since Linne, by the majority of authors (and not only by Swedish 

 ones, as the article in the E. M. M, has it, p. 30 at top). About 

 the i)hilology of the terms derivod from the Greek calypto (I cover) 

 I have added a notice, sub No. IV. 



IV. The Services o{ i\\Q squamae as coverings of the halteres 

 have been for a long time assnmed. There may be some truth in 

 this assumption, but, as far a I know, it has ncver been thoroughly 

 investigated or proved. A ijuaint Interpretation of the use of thesc 

 Organs is found in the old, but very original and praiseworthy 

 publication: 



v Gleichen, gen. Russwurm, Gesch. d. Stubenfliege, 1764, p 16. 



„Mit diesen Schlägeln rührt die Fliege gleichsam die Trommel, 

 wenn sie damit von unten hinauf an die ausgespannten SchallbLäschen 

 schlägt. In welcher Absicht sie dieses thue, wird so leicht nicht 

 ausfindig gemacht werden; vielleicht aber dienet das Geräusche dazu, 

 die Verliebten zusammen zu ruffen." 

 (Translation.) 



„With these drumsticks (the halteres) the fly scems to bcat 

 the drum, whon it strikes from bclow the distended sound-follicles 

 above (squamae). For what purpose the Hy does it, is not easy to 

 find out; the noise may serve to bring together the amorous couples." 



A long interval occurred between this assumption and the opinion 

 of R.-D. who considered the post-alar membrane as a sub- 

 sidiary organ of flight (1830). But as R.-D."s specialty were the 

 Museidae, he did not further devolop his idea for the rest of the 

 Diptcra. Leon Dufour was on the right track when he attempted 

 to establish a relation between the structural inodifications of the 

 post-alar membrane with the organs of breathing and the aero- 

 static bladders existing in the head (bulles cephaliques), 

 in the thorax (utricules thoraci(iuc s), and especially iu the ab- 

 domen of Diptera (ballons ou aerostats). Although he confesses 



