PAPILIONID^. 347 



middle, and orange spots on tlie sides. They change their color at 

 each moult and on reaching maturity are light green, with bold black 

 bands, which partly enclose a number of bright yellow spots. Upon 

 being disturbed, the hirva protrudes a forked scent organ from just 

 back of its liead, which gives off a disagreeable odor. This organ is 

 orange in color and by the manner in which it is used, one might 

 suppose the insect to be venomous. Except, however, for the havoc 

 which the insect sometimes makes in the vegetable garden, it is 

 harmless. 



The caterpillars are exceedingly subject to the attacks of para- 

 sites, and it frequently happens that from one hundred of them, one 

 will obtain but lialf a dozen butterflies. 



An interesting account is given b}^ Mr. Harris in his "-Insects 

 Injurious to Vegetation " of the manner in which the larva of this 

 species prepares for its change into the chr^-salis state and its hatch- 

 ing into the butterfly. He says, " The caterpillars usually come to 

 their full size between the 10th and 20th of July and then measui'e 

 about one inch and a half in length. After this they leave off eat- 

 ing, desert the plants, and each one seeks some sheltered spot, such 

 as the side of a building or fence, or the trunk of a tree, where it 

 prepares for its transformation. It first spins a little web or tuft of 

 silk against the surface wheron it is resting, and tangles the hooks 

 of its liindermost feet in it, so as to fix them securely to the spot ; 

 it then proceeds to make a loop or girth of mau}^ silken threads bent 

 into the form of the letter U, the ends of which are fastened to the 

 surface on which it rests on each side of the middle of its bod3% and 

 under this when finished it passes its head, and gradually works the 

 loop over its back so as to support the body and ])revent it from fall- 

 ing downwards. 



" Though it generally prefers a vertical surface on which to fasten 

 itself in an upright position, it sometimes selects the under side of 

 a liml) or of a projecting ledge, where it hangs suspended, nearly 

 horizontally, by its feet and the loop. 



" Within twenty-four hours after it has taken its station, the cater- 

 pillar casts ofl" its caterpillar skin and becomes a chrysalis or pupa 

 of a pale green, ochre yellow or ash gray color, with two short, ear- 

 like projections above the head, just below which, on the upper part 

 of the back, is a prominence like a pug nose. The chrysalis hangs 

 in the same way as the caterpillar and remains in this state from 

 nine to fifteen days, according to the temperature of the atmosphere, 



