LEPTID^. 237 



" straight liairs standing ol)liquely, and somewhat longer, straight, regularly arranged 

 " stiff bristles, which under the microscope appear like thorns ; the hairs are more 

 " dense than the bristles and both are dark colored, being blackish brown or black, 

 " but on the under side of the anterior tarsi there are numerous isolated per- 

 " pendicular pale fine hairs which are usually rather hooked or bent towards their 

 " tips. On the front tarsi all these hairs exceed the other clothing in length and 

 " occur on all the joints, but are more numerous on the basal joint which also bears 

 " the most numerous thorn-like bristles. I consider that these pale long fine hairs 

 " are ' touch ' liairs, for which I propose the name of ' track ' or ' hunting ' hairs 

 " (pili vestigantes). I notice also that on the two last joints of the front tarsi there 

 " are no bristles and only the straight oblique short hairs and the rather bent 

 " 'hunting' or 'tracking' hairs remain. 



"These hairs also exist on the middle tarsi but are more scarce and do not 

 " exceed the usual oblique hairs and bristles in length, while the hind tarsi have 

 " the ' touch ' hairs entirely absent. 



" These ' hunting ' hairs can readily be seen with moderate magnification and are 

 " plainly visible in dried specimens. 



" The formation of these extraordinarily organised hairs shows that they do not 

 " serve as mechanical means for accumulating foreign bodies near the fly's head, 

 " because assuredly hairs for such a purpose would form a kind of brush. 



" An anatomical examination of these hairs would certainly be of great interest, 

 " but that must remain for others. 



"The 'hunting' hairs will be readily noticed in other Diptera, and among other 

 " things will have a systematic signification. In the last reference I mentioned that 

 " I have observed these hairs in all the specimens of Leptis in my collection, in 

 "some in greater, in some in less numbers. They occur plentifully in Atherix 

 " marginata Fabr. while they are absent in Atherix H/is Fabr.,* and Rondani was 

 " therefore right in putting these species in different genera (he founded the genus 

 " Ibisia for the first in Prodrom, I., 154) even though the 'touch' hairs were 

 " unknown to him. 



"In examining the genera Chrf/sopila, Symphoromyia, and Ptiolina of the 

 " LeptidcB the ' touch -hairs ' are entirely absent. 



" The movements of the front tarsi are remarkable in the species of Tahmms, as 

 " they sit in abundance on the stems of trees, on wooden palings and so on, and can 

 " be easily observed to carry on an extraordinary game with their front tarsi ; they 

 " lift these up from the base and move them as if they were feeling about in the 

 " air, similar to Clivysomyza (Ch/oria) demandata Fabr. which occurs abundantly on 

 " our windows, or like many of the Platystomas and Ghironoviidie. 



" An examination of the front tarsi of Tahanus showed that quite similar ' touch ' 

 " hairs occur as in the Leptidce ; I saw these first in a male of Tahanus hromivs L. 

 " and this showed the same numerous fine ' touch ' hairs on not only the front tarsi 

 " but also on the tip of the tibiae, 



" All the genus Tahanus in my collection show these ' touch ' hairs, sometimes 

 " more, sometimes less. I have not examined other 7\dianidce. 



" I will not decide whether the gropings of these flies aim at espying booty or 

 " whether they are only trying to test the safety of their resting-place, but I believe 

 " that one must incline to the latter opinion. 



" The constancy and the different appearance of the ' touch ' hairs in the genus 

 " Tahanus offer a probable new distinctive character for many species to the 

 " systematic examiner who will make a minute inspection. The great similarity 

 " and arrangement of the ' touch-hairs ' in Leptis and Tahanus seem to me to afford 

 " a new proof of the close relationship of the LepdidcB and Tahanidce. 



'• I could not discover any similar ' touch ' hairs in the above-mentioned 

 " Chrysomyza, Platystoma, and Chironomus, although the movements of their 

 " fi'ont legs agree entirely with those of Tahanus. 



"In conclusion, as a proof that abundant material for examination may be found 

 " in the occurrence of the ' hunting ' hairs on the front tarsi of Diptera, I may 

 " mention that on the front tarsi of Aricia erratica Fall. $ I have found long pale 

 " ' touch ' hairs, resembling those on Leptis, and that further, many Anthomyidas 

 " possess one or more similar long ' touch ' hairs at the base of the basal joint of the 

 " front tarsi. The following will serve as a further example : Ericjone consohrina 



* This Is not quite correct (G. H. V.). 



