64 BUTTERFLIES 



pillar attaches itself by silken threads to the bark of the 

 trunk or branch of the tree. Here it changes to a chrysalis 

 which takes on a color so similar to that of the bark that 

 the insect is surprisingly difficult to discover. A fort- 

 night or so later it changes again into a fully developed 

 butterfly that sallies forth in search of the nectar of 

 flowers. {See plates, pages 67 and 24-0.) 



These "orange dogs," like the caterpillars of other Swal- 

 lowtail butterflies, have curious yellow scent organs which, 

 when the caterpillar is disturbed, protrude from the upper 

 surface just behind the head. These give forth a very dis- 

 agreeable odor which is believed to serve the purpose of re- 

 pelling birds and possibly other enemies. It has been 

 noticed that these caterpillars are not molested by birds al- 

 though they are attacked by various insect enemies. Each 

 mother butterfly is known to be able to deposit four or five 

 hundred eggs and it has been suggested that the injuries of 

 the caterpillars may be checked by shooting the butterfly 

 upon the wing with cartridges loaded with small bird shot. 

 In the South there are several broods in a season. 



The life-history of this species in more northern regions 

 differs in the choice of the food plant and the number of 

 broods. It feeds upon various members of the rue family, 

 including common rue and prickly ash, as well as upon 

 certain poplars and probably other trees. It is two 

 brooded and apparently winters as a chrysalis. The but- 

 terflies of the first brood come from the chrysalis about the 

 last of May and are found on the wing during June. Those 

 of the second brood come from the chrysalis about the last 

 of July and are found on the wing during August and Sep- 

 tember. The length of time required from the laying of the 

 egg to the emergence of the butterfly varies greatly with 



