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XIV. On Diorsis, a Genus of Dipterous Insects, with Descriptions of Twenty- 
one Species. By J. O. Westwoon, Esq., F.L.S. 
Read November 5th, 1833; and November 4th, 1834. 
THE immortal man whose name we, as a body, have adopted as our own, 
terminated his zoological labours by the publication of the “ Dissertatio Ento- 
mologica, bigas insectorum sistens,” scil. Paussus and Diopsis, as though, to 
use the words of his countryman Dalman, “ Linnæo hoc, ut videtur, erat con- 
silium, ut vellet absolvere illustrem suum cursum entomologicum per pro- 
ductum quoddam insigniter singulare, vix quidquam magis singulare ex- 
cogitari potuit quam Paussus et Diopsis.” 
Of the former of these two genera, in its present state, as a family, I have 
given a detailed account, which the Linnean Society has done me the honour 
to publish in the 16th volume of its Transactions. In order to show in some 
degree my sense of this honour, I have taken up the latter genus, and I now 
beg to offer to the Society the present memoir as a fitting companion to my 
former communication ; moreover, the now prophetic, but, at the time, erro- 
neous reference by Illiger to the Linnean Transactions for a memoir upon this 
genus, had a second-rate influence in this choice of subject. 
The cHIEF INTEREST of the genus Diopsis arises from the extraordinary elon- 
gation of the sides of the head into two cylindrical horns, which in some in- 
stances are as long as the whole body, and at the extremity of which the eyes, 
of a semi-globular form, are placed: the antennæ also are inserted near the 
extremity of these protuberances at a short distance before the eyes. At first 
sight these horns might easily be mistaken for antennz ; but they are inarticu- 
lated at the base as well as along the surface; they have, therefore, no inde- 
pendent motion, their movements being necessarily accompanied by those of 
the whole head: when, however, we recollect that they contain not only the 
infinity of nerves of the compound eyes at their extremities, but also those 
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