

304 CRUSTACEA, ARACHNIDES, INSECTA. 



form, and frequently according to the sex, attached to the head, ap- 

 pearing to be peculiarly devoted to a delicate sense of touch, and 

 perhaps to some other kind of sensation of which we have no idea, 

 but which may refer to the state of the atmosphere. 



These animals enjoy the sense of smell and that of hearing. Some 

 authors place the seat of the first in the antenna?, others, in the ori- 

 fices of the tracheae, and Marcel de Serres, &.c. in the palpi; neither 

 of these opinions, however, is corroborated by positive and conclu- 

 sive facts. As to the second, it is only in the Crustacea Decapoda 

 and some few of the Orthoptera, that we can find a visible ear. 



The mouth of these animals presents a great analogy, which ex- 

 tends to those which can only feed by the suction of liquid aliment. 



Those called Tritores or Grinders (broyeurs^, on account of their 

 having jaws fitted for triturating their food, always present them in 

 lateral pairs, placed one before the other; the anterior pair are es- 

 pecially called mandibles; the pieces which cover them before and 

 behind are named labia, and the front one, in particular, labrum. 

 The palpi are articulated filaments attached to the jaws or to the 

 lower lip, and appear to be employed by the animal in recognizing 

 its food. The form of these various organs determines the nature 

 of the regimen with as much precision as the teeth of quadrupeds. 

 The ligula, or tongue, commonly adheres to the lower lip. Some- 

 times, in the Bees and other Hyrnenopterous Insects, it is consider- 

 ably elongated, as are also the jaws, forming a sort of false probos- 

 cis ( promusds} at the base of which is the pharynx, and frequently 

 covered by a sort of sub-labrum, styled by M. Savigny the cpipha- 

 rynx. At other times, in the Hemiptera and Diptera, the mandi- 

 bles and maxillas are replaced by scaly pieces in the form of setae, 

 which are received in an elongated tubular sheath, that is either 

 cylindrical and articulated, or formed with more less of an elbow, 

 and terminated by a kind of lips. In this case they constitute a true 

 proboscis. In others that also live by suction, the Lepidoptera, the 

 maxillae alone are greatly elongated and united, producing a tubular 

 setiform body, resembling a long, slender, and spiral tongue; the 

 remaining parts of the mouth are considerably reduced. Sometimes 

 again, as in many of the Crustacea, the anterior feet approach the 

 maxillae, assume their form, and exercise part of their functions the 

 latter are then said to be multiplied. It may even happen that the 

 true maxillae become so much reduced, that the maxillary feet sup- 



