190 LEPTDOPTERA 



the left side ; ;;/.r' is the sucking-tube ; hph, floor of 

 pharyngeal sac ; pv, pharyngeal valve ; sd, saliv^ary 

 duct ; oe, oesophagus ; fz, dz, frontal and dorsal mus- 

 cles, which hold the sac in position. Fig. 140 shows 

 the sac hung by the five muscles, — dorsal (dz), frontal 

 {fz), and lateral (/s) ; oe is the oesophagus, which ex- 

 tends backward. When the muscles just mentioned 

 contract, the pharyngeal sac enlarges : this causes a 

 vacuum, which is at once filled by the nectar that 

 flows upward through the sucking- tube ; the muscular 

 sac then contracts, and the liquid food is forced back- 

 ward into the oesophagus, the pharyngeal valve pre- 

 venting it from passing downward into the trunk. The 

 second pair of maxillae are reduced in size, but the 

 palpi (PL IX., Fig. 135, x") are large and hairy. The 

 muscle which moves one of these palpi is seen in 

 PL IX., Fig. 140, x", z. 



The legs are very small and weak, being used for 

 supporting the insect, and not much for locomotion. 

 The species Papilio {Ageronia) feronia is an exception 

 to this rule, since, according to Darwin, it uses its legs 

 for running, notwithstanding it is a high flier. The 

 first pair (PL IX., Fig. 135, /'), borne on the weak 

 prothorax, is useless even for supporting the butterfly. 

 The section nearest the body is thickly covered with 

 hairs, for which reason this insect is placed among 

 the brush-footed butterflies, or Nymphalidae (p. 219). 

 Both pairs of wings are well developed, though the first 

 pair is the larger. The distinguishing characteristic 

 of these organs is the thick coating of scales or modi- 

 fied hairs which has given the name of Lepidoptera, 

 (XeTTtg, scale ; -n-Tepov, wing) , signifying scaly wings, 



