The mother butterfly deposits the eggs singly upon the young growth of orange or other citrus fruit trees, generally near the tips of leaves or branches. About a week later each egg hatches into a caterpillar that feeds upon the young leaves, resting upon the lower surface when not eating. After a few days of this feeding the caterpillar becomes too large for the skin with which it was born and it moults, coming forth with a new skin which soon hardens so that it can begin feeding again. A week or so later it moults for the second time, and continues these processes of feeding and moulting until full grown, which is perhaps a month from the time of hatching from the egg. At first the caterpillars eat only the succulent young leaves and branches, but as they grow larger they feed more freely upon the older foliage. They are very voracious and when abundant may often do much damage especially to young trees. When ready to change to the chrysalis each caterpillar 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 fortnight or so later it changes again into a fully developed butterfly that sallies forth in search of the nectar of flowers. (_See plate, page 240._) These "orange dogs," like the caterpillars of other Swallowtail 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 disagreeable odor which is believed to serve the purpose of repelling birds and possibly other enemies. It has been noticed that these caterpillars are not molested by birds although 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 butterflies 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 September. The length of time required from the laying of the egg to the emergence of the butterfly varies greatly with the locality and the temperature. It commonly extends over a period of four or five weeks. [Illustration: _From a drawing by Mary E. Walker_ _See page 62_