368 LECTURE XVI. 



snout in suctorial insects, the long and slender ovipositors of insects 

 which place their eggs in holes of various depths, the soft, setaceous, 

 or plumed antennce, and above all, the palpi, often provided with a 

 terminal vesicle, present the requisite physiological conditions of the 

 organ of touch. Although another sense, and most probably that of 

 hearing, may reside in the antennce, yet no one can witness the use of 

 these organs by bees and ants, the exploratory actions of those of the 

 ichneumon and of many other insects, without recognising in them 

 instruments of the tactile faculty. 



All Mandibulate insects have a process from the labium, within 

 the mouth, so analogous to a tongue as to have received that name. 

 It is particularly well developed in the wasps ( VespidcB), the dragon- 

 flies {Libelliilidce), the grasshoppers {Locustidcp), and certain beetles 

 ( CarahidcB\ in which its soft, finely ridged, upper surface receives a 

 rich supply of nerves. Tt is not present in the suctorial insects, 

 which, as Burmeister well observes, always subsist upon one and the 

 same food, generally inhabit what they feed on, and consequently 

 less require the sense of taste. 



Although a few physiologists have suspected that some part or 

 appendage of the head, and others that the membranous lining of 

 the spiracles were the organs of smell, the precise seat of that sense, 

 which unquestionably exists in insects, has not yet been experi- 

 mentally determined. The application by the common house-fly of 

 the sheath of its proboscis to particles of solid or liquid food before it 

 imbibes them, is an action closely analogous to the scenting of food 

 by the nose in higher animals : and as it is by the odorous qualities 

 much more than by the form of the surface, that we judge of the 

 fitness of substances for food, it is more reasonable to conclude that 

 in this well-known action of our commonest insect, it is scenting, 

 not feeling, the drop of milk or grain of sugar. But no one ever saw 

 an insect present its spiracles to a nutritive substance before feeding. 



The signs of attention and hearing are plainer in insects than 

 those of smelling ; yet the precise organ has not yet been more defi- 

 nitely recognised, unless the structure indicated by J. Miiller* in the 

 fore-leg of the Gryllus hieroglyphus, and more definitely described 

 by Sieboldl in other Orthoptera, be the true seat of the auditory 

 sense. Between the pro- and meso-thorax of the grasshopper and 

 cricket is a double pair of stigmata; one of each pair is conspicuous 

 by its large oval unlabiate aperture, which leads to an infundibular 

 trachea ; close to this large aperture is the second stigma of the 

 ordinary size and shape ; the tracheae from this stigma ramify in the 



* CCXLIV. p. 439. t CCXLV. p. 56—72, tab. I. 



