36 THE BOOK OF BRITISH BUTTERFLIES. 



far as our islands are concerned, for it is a common 

 butterfly on the Continent. 



P. machaon, Linn. (Swallow-tail) (Figs. 12 to 15), 

 though much sought after for the cabinet, is not easily 

 caught, even if the would-be possessor should happen to 

 be in one of the few districts where it may still be 

 found, for it majestically sails along, by the help of its 

 large and powerful wings, with great speed and almost 

 in a straight course, or sometimes soars aloft perfectly 

 safe from the pursuer's net. Why this species should be 

 named after Machaon, a physician, one of the sons of 

 ^Esculapius, who accompanied the Greek army against 

 Troy, it is hard to see ; but the name being once given, 

 it is quite clear why his brother's name, Podalirius, should 

 be bestowed on the second species of the genus. 



The larva (Fig. 14), which is often nearly 2 Jin. long, 

 and feeds on various umbelliferous plants, especially the 

 Marsh Hog's Fennel (Peucedanum palustre), the common 

 Fennel (Faniculum vulgare\ and the wild Carrot (Daucus 

 Carota), should be looked for from June to August or 

 even September. It is a lively green in colour, and 

 carries behind the head a reddish, two-pronged projection, 

 which it can protrude and retract at pleasure, and which, 

 by emitting a strong-smelling liquid, is supposed to keep 

 off its enemies. The head is marked with black, and 

 there is a velvety black band separating the segments, 

 while another crosses the middle of each segment trans- 

 versely. Each of these latter bands bears six orange dots, 

 except the first and the last, on which they are fewer 

 or wanting. A black dot or two below the termina- 

 tion of the bands, and another on each of the legs and 

 claspers, except those of the thirteenth segment, complete 

 the marking of the handsomest representative of our 

 butterfly caterpillars. 



