284 Mr. Westwood on Diopsis, 



producing the sensation of which the antennae are the seat, we can easily 

 imagine how necessaiy it is that the means of communication with the re- 

 mainder of the head should be unbroken by articulations. 



Linnaeus observes that this genus, on account of these ocular peduncles, is 

 distinguished " non a Dlpteris solum, sed ab omnibus etiara insectis hue 

 usque mihi cognitis." Since his day, however, other insects have been dis- 

 covered presenting a somewhat similar formation : of these, the Dipterous 

 genus Addas, Fabr., is nearly allied to Diopsis, and of this M. Gu^rin has given 

 an account, illustrated by very good figures, in the first number of his " Maga- 

 sin (VEntomologie" drawn from the original unique specimen described by 

 Fabricius from the cabinet of M. Bosc, which, I am sorry to say, had suffered 

 materially from the ravages of insects when I inspected it at the Jardin des 

 Plantes*. From M. Guerin's figure it is evident, however, that the eyes only 

 in Achias are fixed at the extremity of the peduncles, the antennae being 

 inserted in the middle of the face : the same remark is also applicable to 

 several other insects with long ocular peduncles, which were at first described 

 by Wiedemann as belonging to the genus Achias, but subsequently formed by 

 him, in a memoir read at the meeting of German Naturalists in 1830, into 

 distinct genera, namely, the Plagiocephalus lobularis and Zygothrica dispar, 

 both brought from Brazil by M. Lund ; to the latter of which (at least to the 

 female) is also allied the Trigonosoma perilampiformis of Gray (GrifF. Anim. 

 Kingd., pi. 128.). In like manner the different species of the Strepsipterous 

 genera Xenos and Stylops, as also the recently established genus Halictophagiis, 

 Curt., have the eyes placed upon very short footstalks. The genus Elenchus, 

 Curt., however, belonging to the same order, does not appear to be so circum- 

 stanced, since Robert Templeton, Esq., who has written and kindly presented 

 to me an account of this genus illustrated by figures, states that the eyes are 

 sessile. Certain male Ephemene are also remarkable for having a supple- 

 mental pair of eyes placed upon short peduncles between the lateral eyes. 



In the order Hemiptera (Heteroptera) De Geer has also figured three spe- 



* The existence of this remarkable genus fortunately does not rest upon this single mutilated spe- 

 cimen, since Dr. Horsfield has been kind enough to show me a specimen of a distinct and very beautiful 

 species with maculated wings, captured by himself in Java ; and amongst the unascertained species 

 at the East India House I noticed the female of this new species, in which sex the head is not broader 

 than the thorax. 



