280 DIPTERA OF NORTH AMERICA. [PART IV. 



Abdomen of the male depressed, subclavate at the tip ; the 

 male forceps is analogous to that of Amalopis and Pedicia in 

 structure j 1 abdomen of the female more cylindrical; upper valves 

 somewhat arcuated, moderately long and broad. 



Dicranota is closely allied to RhapMdolabis and Plectromyia 

 by its 13-jointed antennae and its venation; but it is sufficiently 

 distinguished by the presence of two marginal cross-veins. " While 

 the only known species of Plectromyia has four posterior cells 

 and the two species of Rhaphidolabis five, Dicranota has some 

 species with four and others with five posterior cells. In all other 

 respects, the similitude of the venation of these three genera, 

 which extends to all the relative proportions of cells and veins, 

 is very striking and indicates the closest relationship. 



Two North American species are described by me. The four 

 European species have been sufficiently adverted to above, and I 

 am not aware of any other species of this genus ever having 

 been published, unless it is Limnobia stigmatella Zeft. (compare 

 the foot-note below), which may be a Dicranota. 



The genus Dicranota was first proposed by Mr. Zetterstedt 

 for his D. guerini, in 1840 (Insecia Lapponica, p. 851) ; but that 

 this author did not recognize the true character of the genus 

 appears from the fact that even in his later work D. bimaculata 

 Sebum, is left by him in the genus Limnobia (Zett. Dipt. Scand. 

 X, p. 389T, ?2). 3 Mr. Haliday, in Walker's often quoted work, 

 puts three species under the head of Dicranota: pavida Hal. 

 (syn. guerini ?), bimaculata Sebum., and senilis Hal. The latter, 

 as I have already shown, in 1859, can hardly be & Dicranota, 

 nor can it belong to the Amalopina, if Mr. Westwood's figure 

 (Walker, 1. c. Tab. XXVII, fig. 3) is correct: the subcostal 

 cross-vein is posterior to the origin of the second longitudinal 

 vein ; there is only one marginal cross-vein, and the discal cell is 

 present. The wings are those of Limnophila, but if the antennae 

 are really 13-jointed, it is difficult to decide where this species 

 belongs to. In 1859 (Proc. Acad. Nat. Sci. Philad. p. 249) I 

 described the first North American species of Dicranota, and 

 completed the definition of the genus by noticing its pubescent 



1 This is repeated from Proc. Acad. Nat. Sci. Philad. 1859, p. 249 ; I 

 have not had any fresh specimens for examination since. 



2 In the same work, Vol. X, p. 3843, there is a Limnobia stigmatella Zett., 

 from Lapland, which seems to be a Dicranota with five posterior cells. 



