HARDWICKE'S SCEN CE- GO S SIP. 



231 



auimals which have a joiuted external or cutaneous 

 skeleton. 



If instead of the mouth of a stag beetle we 

 take that of a cockchafer, or better still, that of 

 some predatory beetle, we shall find the maxilla 

 (fig. 145) consists of two lobes, one of which is con- 

 verted into a piercing or cutting instrument, whilst 

 the other forms a soft tactile organ, like a lateral 

 tongue, probably largely supplied with nerves of 

 taste. The maxillse are often sharper than the 

 mandibles, but they are probably never equally 

 powerful when mandibles exist. The paraglossaj 

 are merely a modified second pair of maxillse, and 

 in crickets, grasshoppers, and cockroaches are 

 exactly like the maxilla;. 



All the lateral organs of the mouth have a similar 

 origin, which they share with the lunbs of the 

 insect; hence they are frequently spoken of as 

 modified legs. When the insect is very little 

 developed, a number of exactly similar buds appear 

 on either side of the middle line of the under side 

 of the embryo: of these, some become converted 

 into jaws, and others take the form of legs. Eig. 146 

 represents the young embryo of a crajfish, in which 

 the process of development is precisely similar to 

 that of an insect, as far at least as the formation 

 of the jaws and limbs is concerned. Not only are 

 the mouth-organs and legs developed in tliis manner, 

 but the eyes and antennae have a similar origin ; 

 hence the first three pairs of buds in the figure, 

 marked e, a, and «", represent tlie rudiments of ihe 

 eyes and the two pairs of feelers, or antenna;, of 

 the future crayfish. Those marked md, mx, and mx" 

 represent the mandibles and two pairs of maxillse 

 respectively, whilst those marked /»', i?", jo"', and^"" 

 are rudiments of legs. It is worthy of note that 

 the three pairs of legs which follow the mouth- 

 organs of the crayfish, lobster, crab, &c., are quite 

 intermediate between jaws and legs, partaking 

 equally of the characters of each : these are called 

 foot-jaws. In insects there are no foot-jaws, but 

 some authors think that the three pairs of legs 

 which are constant in all perfect insects represent 

 them. 



The jointed organs, p' and j?" in the figures, are 

 called palpi. The maxillas and paraglossse of all 

 beetles have each one of these organs, and in some 

 beetles there is a second palp on the maxilla;. The 

 palpi are probably tasters ; their hard external 

 sheath is perforated by a vast number of exceed- 

 ingly minute perforations, often amounting to several 

 thousand, each of which leads into a delicate little 

 internal sac, upon which a filament from the nerve 

 terminates. Just as the surface of the tongue of 

 man is extended by the existence of a great number 

 of taste-papilla;, so the palpi of insects are 

 extended by the formation of these little taste-sacs ; 

 so that the same result is attained under very 

 different conditions. 



Turning from the moutii of a beetle to that of a 

 bee, we still find the same essential parts, but 

 instead of the tongue or ligula remaining a com- 

 paratively insignificant organ, it becomes marvel- 

 lously developed (fig. 142). It is no longer rigid, 

 but consists of numerous joints moved by separate 

 muscles. Its extremity is spoon-shaped, and the 

 whole organ is densely covered with hairs, which 

 are capable of being erected by special muscles or 

 pressed flat upon the surface of the tongue. These 

 hairs are of high importance, and aid materially, as 

 will appear in the sequel, in raising the honey to 

 the cavity of the mouth. 



The paraglossse appear quite rudimentary ; but it 

 must be remembered it is probably only their points 

 which are seen as separate organs, the greater 

 portion of them being frequently united to the 

 mentum to form the base on which the great tongue 

 rests. This is evident, because the palpi which 

 really belong to the paraglossse, or tongue-sheaths, 

 then come from the back of the mentum, which is 

 more correctly designated the labium, on account 

 of its compound nature. The labial palpi, or those 

 which properly belong to the paraglossse, are organs 

 of considerable importance : they serve at least as 

 tongue-cleaners, affording the insect a ready means 

 of clearing the hairs on the tongue, of pollen, 

 whilst they probably possess considerable sensibility 

 of a special kind, perhaps, enabling the bee to taste 

 the nectar which it is about to lap into its mouth by 

 the aid of its enormous tongue. 



The labial palpi have also a third function, for 

 they form a portion of the walls of a tube, chiefly 

 composed of the maxillse, which incloses the base of 

 the tongue when in action. 



The maxillse are also very highly developed, as 

 will be seen by a reference to the figure. Each con- 

 sists of a large outer knife-shaped lobe, mx , 

 strengthened by a prominent rib along its inner 

 margin ; of a small inner lobe, densely covered with 

 sensory hairs, mx"" ; of a basal sheath, r,ix^ ; and a 

 rudimentary palpus, mx^. 



The great outer lobes are of great importance. 

 First, they form the roof the mouth-tube, the base 

 of which consists of tiie mentum and labial palpi. 

 The labrum completes the roof of this tube between 

 the basal joints of the maxillse only, the ridge-like 

 edges of these organs being in close apposition, 

 when the insect is feeding, in front of the labrum. 

 A tube then is formed, in which the tongue lies, 

 and from which it protrudes when it is extended to 

 its full length. The tongue is capable of being 

 entirely withdrawn into the tube, except its spoon- 

 shaped extremity, which then lies between the 

 terminal joints of the labial palpi. 



The act of suckiug takes place in the following 

 manner. The bee presses the maxillse, inclosing 

 the other parts, to the base of the nectary of a 

 flower in which the honey lies, and then extends its 



