INSECTS. 281 



For touch, in some Insects the sucker serves as the organ ; in 

 others the palps which belong to the organs of the mouth, in many 

 the antenna. Of taste, smell and hearing, little is known. Taste 

 has its seat in the internal surface of the mouth. In some Insects 

 there is a part present, which may be compared to a tongue 1 . 

 Respecting smell different opinions are offered. On theoretical 

 grounds, from presumed analogy with vertebrate animals in which 

 the first pair of cerebral nerves always goes to the olfactory organ, 

 BLAINVILLE has concluded, that the antennae, to which the first 

 nerves from the cerebral ganglion proceed, must be the organs of 

 smell 2 . B ASTER, REIMARUS, DUMERIL and STRAUS place the 

 sense of smell in the air-slits (stigmata), which admit the external 

 air to the air-tubes. TREVIRANUS however has with reason alleged 

 against this opinion, that the stigmata, inasmuch as they are 

 dispersed over the body, must be useless for determining the place 

 from which the odorous matter proceeds ; also that in Insects, which 

 have no stigmata and which respire by tracheal gills, it would be diffi- 

 cult thus to account for the sense of smell. ROSENTHAL discovered 

 in flesh-flies (Musca carnaria) a red-brown, folded membrane, which 

 is situated in the head beneath the setting on of the antennae 3 . 

 TREVIRANUS thinks that in sucking Insects, which are especially 

 distinguished by their acute sense of smell, the seat of this sense 

 ought to be sought for in the sucking organ itself, or in the 

 oesophagus. If these animals suck in air, then they may smell 

 with the same organ, by means of which, when they imbibe fluids, 



For the theory of vision with compound eyes it is necessary that the partial images 

 be erect; hence JOH. MUELLER (Zur vergl. Physiol. des Gesichtsinnes) has concluded 

 that insects see with their compound eyes not by refraction of the rays, but by keeping 

 separate the rays of light that come from different points. Hence he denies to the 

 fagettes of the cornea, which are true lenses, a refractive power ; yet that vision in 

 insects with compound eyes occurs by dioptric means, has been shewn by Dr. A. 

 BRANTS, and established" by means of an instrument constructed on the plan of the 

 insect's eye. Tijdschr. voor natuurl. Geschied. en Physiol., XD., 1840, pp. 12 56, 

 PI. I. 



1 See this part figured and described in some hymenopterous insects by G-. R. 

 TREVIRANUS, Verm. Schriften 11. s. 125, 131 133, Tab. xin. fig. i, L, fig. 4, 7 ; Tab. 

 iv. fig. 5, 7, 8, 9, L' and L. 



2 See DUGES, Physiol. compar. I. 1833, pp. 157 161, who endeavoured to establish 

 the same views by experiments, as also LEFEBVRE, Ann. de la Soc. entomol. de France, 

 1838. 



3 BEIL'S Archivf. die Physiol. x. s. 427 439. 



