26 



NATURAL HISTORY. 



only be detected in the larva state by a careful and difficult examination, are now easily to be 

 discerned on the outside of the horny envelope of the pupa. But the pupa has no other limbs, and is 

 usually incapable of any function of life, except breathing, or of any motion, except a slight wriggling 

 of the segments of the abdomen. But there are exceptions ; some pupse are able to move about 

 in their cocoons, and those formed in the trunks of trees are provided with small hooks by 

 which they can work themselves along their galleries, and push the head of the pupa through the 

 partition, so that when the Moth emerges it finds itself completely at liberty. The pupa of a Cuban 

 Moth (Conchylodes diphtheralis") lies on the ground without any protection, but possesses the power 

 of leaping actively about. 



A pupa consists of the thorax, which is the thicker portion, and of the abdomen, which consists 

 of nine movable segments jointed together. The seams in the thorax more or less distinctly indicate 



the parts of the future Butterfly. The head is 

 visible as a slight swelling in front. It is pressed 

 downwards, and the eyes are visible on each side. 

 Behind and above this is the thorax ; and the 

 lower joints of the two first pairs of legs are placed 

 on the under side in front, on the sides of the head. 

 The antennae pass round the eyes, and run back- 

 wards outside the middle pair of legs. The wing 

 cases, which vary in length in different species, lie 

 on the sides of the pupa. In. the large Sphinges,. 

 the proboscis is often furnished with a separate 

 sheath, sometimes convoluted, lying in front of the 

 breast. 



The position of the spiracles is the same in 

 the pupa as in the larva ; but not only are the 

 external organs of the future imago developed 

 during the pupa state, but the digestive and 

 CHRYSALIS MAGNIFIED AND PARTIALLY OPENED TO SHOW nervous systems are profoundly modified, assuming 

 RUDIMENTARY WINGS (), ANTENNA (b), AND OTHER the form which they present in the perfect insect. 



During the first stages the pupa appears to be filled 



with a milky fluid, in which the rudiments of the future insect can scarcely be distinguished ; but 

 these rapidly acquire consistency, an evaporation, or rather transpiration, taking place constantly, by 

 which the weight of the pupa is eventually much reduced. 



The duration of the pupa state is very different in some insects : but except in the case of 

 summer broods of double-brooded insects, when it frequently lasts only a few days, it extends over 

 several months, for the insect usually passes the winter in this condition. In some cases, especially in 

 the Small Eggar (Eriogaster lanestris), the pupae do not all disclose the perfect insect the same season ; 

 but the insects of the same brood appear a few at a time each year, up to fourteen or fifteen years 

 afterwards. The reason for this is obvious in the case of the Small Eggar, for the Moth appears 

 during the inclement month of February, and if all the pupse belonging to the same brood disclosed 

 the Moth during a single season, the species would be liable to extinction in the event of unusually 

 severe weather. 



When the Butterfly or Moth has arrived at maturity, the pupa cracks along the seams, and the 

 perfect insect works itself out, discharging a few drops of fluid at the same time. In some insects 

 this is of a reddish colour; and when the insects were unusually numerous the red spots used 

 occasionally, in superstitious ages, to give rise to the idea that a shower of blood had fallen. In the 

 case of insects enclosed in a cocoon this fluid serves to moisten the silk, or to exert a chemical action 

 upon it (for it is acid, at least in some cases), in order to facilitate the escape of the Moth. Some of 

 the larger Bombyces are actually provided with a strong spine under the wings, which helps them to 

 force their way out of the cocoon. As the cocoon is useless for mercantile purposes after the 

 emergence of the Moth, silk-growers always kill the insect before unwinding the silk, by throwing it 

 into boiling water, which likewise renders the silk itself more manageable. 



