292 DIPTERA OF NORTH AMERICA. [PART IV. 



otherwise would probably be overlooked by entomologists who 

 have not made the Tipulidse their especial study. 



The structure of both male and female genitals of the Cylin- 

 drolomina shows some peculiarities which deserve to be noticed. 



In the forceps of the male Cylindrotomina which I have had 

 an opportunity to examine, the claw-shaped horny appendages 

 inserted at the tip of the movable basal pieces do not meet or 

 overlap each other, as usual. In the state of repose they are 

 folded backwards, like the blade of a penknife, towards the upper 

 side of their basal pieces. A very characteristic, long, horny, 

 linear organ, which I have called aculeus, usually protrudes 

 when the forceps is opened, and sometimes remains hanging on 

 the outside even in dry specimens. This organ consists of three 

 slender horny styles, connate at their basis, which is especially the 

 case with Phalacrocera tipulina ; each of the styles has a knob 

 at the tip in Cyl. nodicornis 0. S. and in Triogma; in Cylindro- 

 toma americana these styles are so far connate that the aculeus 

 assumes the shape of a lamella with three sharp points at its tip, 1 

 separated by deep indentations. 



The ovipositor of the female is distinguished by its short, broad, 

 foliaceous valves, rounded at the tip. Nothing similar is to be 

 found among the Tipulidee. The ovipositor of Cyl. distinc- 

 tissima has a still more complicated structure, which will be 

 described in its place. 



2. Historical Account. '- 



The history of this group is short, as the recognition of its true 

 characters is only of recent date. The principal European Cylin- 

 drotomina were known for a long time before any connection was 

 discovered between them, and on the other hand the genus 

 Cylindrotoma was first established and long maintained, upon a 

 purely artificial character, which caused many foreign elements 

 to be introduced in it. 



The genus Cylindrotoma has been adopted byMacquartin 1834 

 (Hist. Natur. des Dipt. Vol. I, p. 10T) ; he formed it out of two 

 European (distinctissima and macroptera) and a North American 



1 The forceps of the European Cyl. glabrata Meig. seems to be built upon 

 a different plan ; but I cannot well judge of it from a single dry specimen. 

 The structure of its aculeus, as far as I could perceive, is the same as in 

 Cyl. nodicornis 0. S. 



