STRUCTURE OF INSECTS. 259 



Crustaceans, the antennae are not ranked among the append- 

 ages strictly so-called. This is no pedantic distinction, but 

 rests on the fact that their development is different from 

 that of the jaws and legs. 



It was a step of some importance in morphology when 

 Savigny showed that the three pairs of appendages about 

 the mouth were homologous with the other appendages, ?.«., 

 were masticatory legs. 



(i.) Furthest forward lie two mandibles, the biting and 

 cutting jaws. These are single-jointed, and thus differ 

 from the organs of the same name in the crayfish, which 

 bear a three-jointed palp in addition to the hard basal 

 part. In those insects which suck and do not bite, e.g., adult 

 butterflies, the mandibles are reduced. 



(2. ) Next in order is \he. first pair of maxilla. Each maxilla 

 consists of a basal piece (protopodite), an inner fork (endo- 

 podite), and an outer fork (exopodite). I use these names 

 from Crustacean terminology, after the example of Marshall 

 and Hurst. The entomologists divide the protopodite into a 

 lower joint 'Cc^&cardo, and an upper \kvt stipes, the endopodite 

 into an internal lacinia, and an external galea, while the 

 exopodite is called the maxillary palp. 



(3.) The last pair of oral appendages or second maxillm are 

 partially fused, and form what is called the labium. The lower 

 and upper joints of their fused protopodites are called sub- 

 mentum and mentum; the endopodites on each side are double 

 as in the first maxillae, and consist of internal lacinia and 

 external paraglossa ; the exopodites are called the labial 

 palps. 



The three pairs of thoracic legs consist of many joints, 

 are usually clawed and hairy at their tips, and vary greatly 

 according to their uses. Think, for instance, of the hairy 

 feet by aid of which the fly runs up the smooth window-pane, 

 of the muscular limbs of grasshoppers, of the lank length of 

 those which characterise " daddy-long-legs," of the pollen- 

 baskets on bees, of the oars of water-beetles. In identifying 

 insects from a book it is needful to recognise the joints of 

 the legs by the names which entomologists have transferred 

 to them from human osteology, viz., the superior coxa with 

 projecting trochanter, the stout femur, the tibia, and finally 

 numerous tarsal joints. 



