5 



jectives the adverbs proximad (towards the proxitaal end) 

 and distad (towards the distal end) are formed. 



Examples. — Th^ proximal segment of the leg of an insect is the coxa. 

 The segments of the leg distad of the tibia constitute the tarsus. 



Aspects of appendages. — In addition to the two ends 

 of an appendage four aspects are recognized. To these the 

 same terms are applied as to the corresponding aspects of 

 the body : viz.^ dorsal, ventral, cephalic, and caudal. It is 

 therefore necessary to have a rule by which the correspond- 

 ence between the aspects of the body and of appendages can 

 be determined. In other words, a definite position must be 

 chosen as the normal position of an appendage. Naturalists 

 are quite well agreed as to what is the normal position of 

 the limbs of the Vertebrates. The following are what we 

 believe to be the analogous positions for the legs and wings 

 of insects.* 



{a,) Wings. — Extended horizontally at right angles to the 

 body as are the wings of a dragon-fly (Libellula) when at 

 rest. 



{b!) Legs. — Extended horizontally at right angles to the 

 body so that the convexity of the articulation between the 

 two principal segments of the leg (femur and tibia) shall look 

 dorsad ; and so that the surface of the tarsus (" foot") which 

 is usually applied to the ground when walking shall look 

 ventrad. 



The dorsal, ventral, cephalic, or caudal aspect of a wing or 

 leg is that aspect which, when the wing or leg is in its normal 

 position, looks in the same direction as does the aspect of 

 the body which bears the same name. 



First, second, third, etc. — When the members of a 

 series of parts forming a portion or the whole of the trunk 



* The necessity for referring to the aspects of other appendages than the legs 

 and wings will so seldom arise that it does not seem worth while to attempt to 

 determine the normal positions of such appendages. 



