93 



DIPTERA. 



Syn. Diopsis Tndica, Westw. in Trans. Soc. Linn. vol. 17, p. 299. 

 Diopsis Ichneumonea, Donovan, 1st edit. 



The appearance of this curious insect is peculiarly striking. Nothing can be 

 more singular than the disposition of the eyes, which are situated at the extremity 

 of two long immoveable pedicles arising from the head, most exactly in that part 

 which in other insects bears the antennas. In this particular the Diopsis differs not 

 only from other insects of the kindred genera, bat also from all the other kinds we 

 are acquainted with. Some few of the Cancri, &c. have indeed the eyes placed at 

 the extremity of elongated pedicles, as is, for example, instanced in the Cancer angu- 

 latus, yet these are obviously dissimilar in construction, for they are moveable at the 

 base, and may be directed towards any object, at the will of the animal, with the 

 utmost facility ; but to accomplish this, the motion of the pedicle in the Diopsis must 

 be necessarily accompanied by that of the head, or even of the whole body. The eyes 

 of the latter are notwithstanding so conveniently stationed at the globular extremity 

 of the pedicles, as to embrace a far more comprehensive range of sight than is usual 

 with the generality of insects. 



To the inexperienced entomologist, the Diopsis would rather seem to be furnished 

 with remarkable horns, and to be destitute of eyes, although the latter are so very 

 conspicuous when they are pointed out ; it is, on the contrary, the true horns, or 

 antennas, that are so minute as to be most likely to escape attention, for each of these 

 consists only of a single setaceous hair, or bristle, seated on a very small tubercle 

 just beneath the eye. 



It has been previously intimated, in the observations on the genus Paussus, that 

 the first account of the Diopsis was inserted in a small tract published by Linnasus, 

 at Upsal, in 1775. From this we learn, that both the Diopsis and the Paussus were 

 found by Andreas Dahl, among a parcel of insects in the possession of Dr. Fothergill, 

 of London, by whom they were sent to Linnasus. These consisted chiefly of insects 

 collected in North America and Guinea, but the habitat, either of the Paussus, or the 

 Diopsis in particular, it is very certain was by no means exactly known. Fuessly 

 notwithstanding describes the D. ichneumonea, upon this ambiguous authority only, 

 as a native of Cayenne, and after him Gmelin notes the same insect from South 

 America, and Guinea, perhaps with as little reason. Latreille tells us it is from the 

 coast of Angola, on the information of Perrin. a zealous naturalist of Bordeaux. 

 Donovan's specimens of the insects here figured, and which he says are most 

 assuredly the Diopsis ichneumonea of Linnasus, were brought from Bengal, where they 



