234 INSECTS. 



gans of locomotion; but the animal retains its habits and activity. 

 In the perfect or complete transformation, on the contrary, the 

 larva is so different from the perfect animal that nothing but 

 ocular evidence of the change can convince of its identity. The 

 pupae of this metamorphosis, although their forms are short- 

 ened and somewhat similar to those which they are to acquire 

 in their last change, take no food, remain immoveable, and give 

 no external sign of life. The term chrysalis is applied by 

 many writers to insects in the pupa state. 



The period insects continue in the pupa state is various. Some 

 species remain only a few days under this form, others as many 

 months, or even years. Each, however, has in general a stated 

 period, which is seldom or never exceeded. As Lamarck has 

 observed, there seems between the insect races and the vegeta- 

 ble kingdom a correspondence of developement. The larvae 

 are produced from the ova when the food of many, the leaves 

 of plants, begin to appear; and the perfect insect from the 

 same larvae, as in a great portion of some orders, appears in its 

 changed form, when food adapted to the animal is prepared in 

 the nectaries of the expanded flowers. The duration, however, 

 of the pupa state may be prolonged in certain cases beyond 

 the average term. Thus it has been found, that, according as 

 the insect becomes a pupa at an earlier or later period of the 

 season, it will remain in this state for a few weeks or several 

 months, according to circumstances. The caterpillar of the 

 Papilio machaon, one of those which have a double brood in 

 the year, if it becomes a pupa in July, the butterfly will appear 

 in thirteen days ; if not until September, it will not make its 

 appearance until June in the following year. The same is the 

 case with a vast number of other insects, and their developement 

 has been thus discovered to depend much on the temperature of 

 the season, or, which is the same thing, on the developement of 

 plants destined to afford them protection and support. In the 

 month of January Reaumur placed several of the pupae of moths 

 and butterflies, which would not naturally have been developed 

 till the following May, in a hot-house, and the result was, that 

 the perfect insects made their appearance in a fortnight, in the 

 depth of winter ; and by other experiments he ascertained that in 

 this high temperature the change was accomplished in five or six 

 days, which would have required as many weeks in ordinary cir- 



