AND THEIR TRANSFORMATIONS. 25 
is of a creamy-white on the upper side, the tip of the fore wings having a very slight fuscous dusky or black 
irregularly defined mark, not extending along the entire margin of the wing. On the under side this mark is 
replaced by a pale yellow mark, and the hind wings on the under side are also yellow, thickly spotted towards 
the base with black atoms. The males have moreover a black spot, and the females two round spots on the 
upper side of the fore wings, and both sexes have two black spots on their under side. The females have often 
also an elongated patch on the inner margin of the fore wings above, and there is a slight black mark on the costa 
of the hind wings. All the markings vary greatly, and some females have the upper side dirty pale buff, 
If the perfect insects of this and the first species, P. Brassiex, thus agree so closely together, their prepa- 
ratory states are totally unlike, affording reason to believe that the specific distinctions of the other presumed 
species might also be better determined by their preparatory states. The eggs of this species are placed singly, 
and not in clusters, upon various species of Brassica, Reseda, &c. ; the caterpillars are pale green, with a slender 
yellow dorsal line, and an interrupted yellow line above the feet on each side, in which the spiracles are placed ; 
the head, feet, and tail, are also entirely green ; the body is transversely wrinkled, and the segments are but 
slightly indicated. Under a lens the whole body is seen to have a vast number of very minute black tubercles 
arranged in transverse rows. It feeds on the interior leaves of the hearts of cabbages, &c., it is therefore much 
more obnoxious than P. Brassicee. It is from this circumstance well known in France under the name of the 
cer du coeur. 
The mode in which the transformation of this insect from the caterpillar to the chrysalis state is effected, has 
been carefully described by Reaumur. Having attached itself by the hind feet to the little bundle of silk at the 
tail, and suspended itself by a silken skein across the middle of the body, in the manner described in our obser- 
vations on P. Brassic, it remains for about thirty hours unchanged, or rather the change is going on beneath 
the skin of the caterpillar, which gradually becomes of a dusky colour, owing to the separation of the body of 
the chrysalis within ; the throwing off of the skin is effected very rapidly, “c'est Vaffwire d'un instant,” says 
Reaumur. After a variety of contortions the skin of the back slits near the head, and forms a passage sufficiently 
large for the passage of the whole body of the chrysalis. When the head of the chrysalis is disengaged, it rests 
upon the old skin of the caterpillar, but it remains now to draw the hind part of the chrysalis out of the slit, 
or what is the same thing, to push back the caterpillar skin until it becomes a crumpled mass near the spot 
where the two hind legs are fixed ; this is effected by the alternate lengthening and shortening of the chrysalis. 
The skein of silk across the body is now seen to offer but little obstacle to the pushing back of the exuvie by 
the contraction of the rings of the chrysalis. When the exuvia has been pushed back so as to cover only 
about one-third of the length of the chrysalis, the insect ceases this operation, it being more convenient for it to 
withdraw the extremity of the chrysalis out of the aperture (being upheld by the transverse girth), and then 
push it back outside the exuvie till it reaches the little bundle of silk, into which it fixes the little hooks at the 
extremity of the tail. It then rids itself of the exuviw by a semicircular movement of the extremity of the 
abdomen, which is at the time curved, whereby it pushes the exuvia out of its old position and breaks the 
threads of silk to which it was attached, when it falls down. The chrysalis then remains quict, being fixed 
exactly in the same situation and manner as the caterpillar. The chrysalis is yellowish, greenish-grey, or 
brownish, often with three sulphur yellow lines. 
According to Mr. Stephens, the first brood appears at the end of April, and the second about the beginning 
E 
