Probably the commonest food plant of the caterpillars is the Dutchman's Pipe or Aristolochia, which is frequently planted as an ornamental vine for porch adornment. It also feeds upon wild ginger or Asarum and probably upon other plants. A dozen or more eggs are laid upon a leaf by the mother butterfly, usually in a cluster or grouped near together. They hatch a week or so later into small brownish caterpillars which remain together for awhile in little groups that feed side by side upon the leaf, beginning at the margin and working toward the centre. As they become larger they feed more freely and gradually disperse so that each forages for himself. As they approach maturity their appetites become voracious and their presence is often shown by the defoliated condition of the branches. They have back of the head the osmateria or scent organs which are commonly found in the other caterpillars of this genus, but the odor emitted by them is likely to be less pronounced than usual. [Illustration: TWO OF THE SWALLOWTAILS (Three fourths natural size) The Palamedes (_see page 76_) The Giant (_see page 62_)] [Illustration: _See page 67_ THE GREEN-CLOUDED SWALLOWTAIL Upper surface above; lower surface below] When full grown the caterpillars find such shelter as they may and each spins a bit of silken web and a silken loop which hold it while it changes to the chrysalis. This chrysalis is very likely to take on the colors of the immediate surroundings and thus be rather difficult to see. If the egg was laid by one of the spring or early summer butterflies, the chrysalis will soon change to a butterfly which will appear toward midsummer and which may lay eggs for another brood of caterpillars. These caterpillars mature to chrysalids the same season and some of them are believed to change into butterflies in autumn, these butterflies hibernating through the winter; while others are believed to remain unchanged through the winter and disclose the butterfly the following spring. This is an exceptional condition for the Swallowtails and it is worth while to make careful observations along its northern limits to learn more definitely the facts as to the winter condition. =The Green-clouded Swallowtail= _Papilio troilus_