424 ZOOLOGY. 



exist often great differences between the male and the female : 

 the common lampyris has already offered us an example 

 (Figs. 444, 445). Almost all insects lay eggs : nevertheless, 

 some are viviparous. There often exists at the extremity 

 of the abdomen of the female a dart, a wimble, or some other 

 organ, destined to form holes adapted to receive the eggs ; and 

 by an admirable instinct the mother uniformly deposits these 

 in a place where the young will find themselves in proximity 

 with the food they require, even although it be in most cases 

 not the kind which the parent lives on. 



In youth, insects change their skin several times, and pre- 

 sent almost always a phenomenon of the most remarkable 

 kind, of which, however, we have already seen an example in 

 the batrachia. Most of them, on quitting the egg, neither 

 resemble their parents nor what they will themselves after- 

 wards become, and undergo, before arriving at the perfect 

 state, changes so considerable as to constitute a true meta~ 

 morpkosis. 



Fig. 446. Swallow-tailed Butterfly (Larva of the Butterfly Machaon). 



In general, insects pass through three conditions, quite 

 distinct, which have been named the larva state or condition 

 (Fig. 446), the nymph state (Fig. 447), and the perfect state 

 (Fig. 448); but the changes they undergo are not always 

 equally great. Sometimes these changes render the animal 

 altogether unrecognisable, at other times they consist only 

 in the development of wings ; and these various degrees of 

 transformation are known by the names of complete meta* 

 morphoses or of semi-metamorphoses. 



531. Insects which undergo a complete metamorphosis 

 are always more or less vermiform when they leave the egg 

 and when they are in a state of larva (Fig. 446). Their body 

 is elongated, almost entirely soft, and divided into moveable 

 rings, of which the regular number is thirteen. Sometimes 

 they are altogether without limbs : at other times they have 



