814 INSECTA. 



element more suited to their future existence. The coccinellce and others fix 

 themselves by the anus under leaves or twigs ; others suspend themselves by 

 a silken thread ; and a very great number enclose themselves in cases or 

 cocoons composed of silk and other materials, to undergo their final change. 

 The second form in which insects appear is the pupa or nympha state. In 

 this, the number of the exterior organs of the animal is augmented or 

 developed anew. Linnaeus presents the forms uiider which insects appear 

 in this state under five heads. The whole, however, may be reduced under 

 two heads : first, those in which the transformation is partial ; and secondly, 

 those in which it is complete. 



The influence which the partial metamorphosis exercises on the body is not 

 sufficiently powerful to destroy the typical form proper to the species, and is 

 modified only by slight alterations. An experienced eye which has seen the 

 animal in its first stage of life, can still recognise the individual. The prin- 

 cipal change takes place in the exterior members, and particularly in the 

 organs 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 pupse of this metamorphosis, 

 although their forms are shortened, and somewhat similar to those which 

 ihey 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 remam only a few days under this 

 form, others as many months, or even years. Each, however, has in gene- 

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

 observed, there seems between the insect races and the vegetable 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 per- 

 fect 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 nec- 

 taries 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 Avill 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 



