Fm. 1, 1865.] 



SCIENCE-GOSSIP. 



31 



for she folds lier wings together on his 

 approach, and then the flirtations, pursuits, 

 refusals, and pretended departures commence 

 again. 



These performances sometimes last for 

 more than half an hour, no inconsiderable 

 portion of a butterfly's lifetime. When they 

 have ended, the female deposits its eggs, 

 several hundred in number, upon some por- 

 tion of a cabbage-leaf The eggs are like 

 little pyramids, three or four times as high as 

 wide, and grooved by deep channels, which 

 separate the rounded, undulating sides from 

 each othei". The Pieris arranges its eggs in 

 a most artistic manner, side by side, and, 

 having glued them firmly to the leaf, leaves 

 them entirely to their fate. By far the 

 greater number of them perish, but still some 

 are hatched, and thus insure the perpetuation 

 of the species. 



Every one knows that there springs from 

 each of these eggs a worm-like animal called 

 a caterpillar, which must pass into the inter- 

 mediate condition of chrysalis before it will 

 become a perfect butterfly. 



The egg which our Pieris lays is much 

 smaller than a millet-seed, and the caterpillar 

 which emerges from it is proportionally dimi- 

 nutive. When fully formed, however, it 

 measures one inch and a half in length, and 

 about l-5th of an inch in width, and l-6th in 

 depth. V/e see what a great difference there 

 is in size between the animal when it emerges 

 from the egg, and when it is fully formed, 

 and how rapidly the increase takes place. 

 Moi'eover, this growth is not gradual, as in 

 most other animals. We may describe it as 

 occurring suddenly, and by a series of forma- 

 tive leaps taken at each of those periods 

 ordinarily called moultings. In fact, as soon 

 as it leaves the egg the young caterpillar eats 

 with a vora.city too familiar to our gardeners, 

 but, nevertheless, does not increase in size. 



After some days this enormous appetite is 

 lost ; the caterpillar becomes quite languid, 

 and its skin loses its colour and appears to 

 wither. It then crawls av/ay to some 

 sheltered locality. If we follow it to its 

 retreat, we shall see it attach itself firmly to 

 the ground, alternately contracting and infla- 

 ting its body and twisting it about in every 

 way ; then resting for a while, as if com- 

 pletely exhausted, and finally commencing 

 anew. Sometimes whole hours are spent 

 before we can see the object of all these tire- 

 some operations. Eventually the skin bursts 

 at the third or fourth ring, and splits in a 

 straight line from one end of the body to the 

 other. The caterpillar now pushes out first 



its head and afterwards its entire body, and 

 appears in a new skin as flexible and as 

 brilliantly-coloured as ever. It has also 

 increased in size, so that it would be quite 

 impossible to enclose it in the case which 

 before enveloped it. Its organs have increased 

 in volume, but having been pent up and 

 compressed by the old skin, when suddenly 

 liberated they attained their proper size, as ib 

 were, through their natural elasticity. 



There are several moultings gone through 

 before the caterpillar arrives at its adult size 

 and acquires its final characters. At this 

 period we can distinguish but two anatomical 

 regions in our insect — the head and the trunk. 

 The head is small, of a blue colour picked 

 with black, covered with a hard skin, and 

 provided with six simple eyes, which are 

 quite separate from each other. The mouth, 

 as in other caterpillars, is formed for dividing 

 and chewing the tough leaves of cabbage and 

 other cruciferous plants. It is provided 

 laterally with a pair of solid horny mandibles, 

 and a pair of less powerful jaws, which are 

 partly concealed by an upper lip and a wide 

 lower one. In the middle of the latter may 

 be seen a small tubular elongated organ, 

 pierced by a microscopic aperture ; this is the 

 spinning apparatus, by which is made the 

 soft wool-like material which the animal will 

 soon require. 



The body of the caterpillar is of cylindrical 

 form, and is composed of twelve almost similar 

 rings. It is of a greenish or yellowish grey 

 colour, marked by three yellow bands which 

 pass from end to end, and is covered with black 

 spots. These spots are little tubercles, each 

 of which carries a white hair, easily seen with 

 a pocket lens. There are eight pairs of feet 

 for the purpose of locomotion, and, as in all 

 caterpillars, these are of tv»ro kinds. The three 

 first of each side are conical, jointed, and ter- 

 minated by booklets or little claws ; these are 

 the horoiy or true feet. The others are termed 

 membranous or false feet. The latter are 

 like large tubercles, whose ends are truncated 

 and furnished with a circle of booklets. The 

 most remarkable feature in connection with 

 these is, that the caterpillar can move them 

 in every direction, can push them out, or 

 draw them into the body so completely that 

 there is hardly a trace left of the positions 

 they occupied. There is on each side of its 

 body and extending over ten segments, a 

 series of little orifices, each of which is sur- 

 rounded by a brown circle ; these are the 

 stigmaM, or apertures through which the air 

 is admitted to the respiratory organs. 



The caterpillar of the cabbage butterfly 



