508 THE ANIMAL KINGDOM. 



larva resembles its parent in most respects, except in the number of 

 antennal joints, of facets in the eye, absence of wings, and want of maturity 

 of the sexual organs. In the Hemi-metabola, the larva may differ notably 

 from the adult in the structure of the antennae, eyes, mouth-parts, shape 

 and disposition of the body-somites, especially the thorax, as well as in 

 the absence of wings and in internal structure. It is aquatic and possesses 

 special contrivances for respiration. The characters of the adult may be 

 acquired gradually or quickly. In the Metabola, three well-marked stages 

 are distinguishable, larva, nymph or pupa, and imago. The larva may be 

 Campodeiform, or cruciform (see p. 150), with or without limbs ; its antennae 

 differ much from those of the adult ; its eyes are ocelli ; its mouth- 

 parts may be similar (not identical) or very dissimilar to those of the 

 adult. It passes into a pupa-stage, w r hich becomes the imago in one, 

 rarely in two moults. The pupa is quiescent for the whole or part of its 

 existence (p. 152), and profound changes take place leading to a re-con- 

 struction more or less complete of organs external as well as internal, 

 together with the development of structures peculiar to the imago (wings, 

 genitalia). In a few instances (Mantispa among Neuroptera, Meloidae 

 among Coleoptera) there is a hyper-metamorphosis. The first larva is 

 Campodeiform, the second more or less cruciform. Much variety in the 

 details of metamorphosis are noticeable. 



Alternation of Generations is coupled with parthenogenesis, and is 

 known in this case as Heterogamy. Dimorphism is common, and falls 

 under several heads : (i) sexual when the male and female differ markedly, 

 a form of dimorphism sometimes connected in Lepidoptera with change 

 of locality : (2) seasonal when the imago produced at one time of the 

 year differs from that produced at another seen in the summer and 

 winter broods of some Lepidoptera : (3) functional, e. g. winged and apterous 

 viviparous Aphidae> the small female or worker in the colonial Hymenoptera 

 (Bees, Wasps, Ants) or the arrested male and female workers and soldiers 

 among the Termitidae (White Ants 1 ). 



Some Coleoptera are phosphorescent, and the light is produced by 

 special organs lodged in the head (E later idae) or in the abdomen (Lampy- 

 ridae). Some insects live in colonies, e. g. the social Hymenoptera (Bees, 

 many Wasps, Ants), the White Ants, some Lepidopterous larvae. A 

 great variety of structures are found, made for protection during pupation 

 or for rearing the young. Many insects possess the power of emitting 

 sounds, caused by the friction of external parts or of special organs 

 (Cicada among Homoptera), by the motion of the wings in flight, by the 



them, but accords with Brauer's views as to Classification (infra} and the results of recent researches. 

 Compare the general works cited p.. 146. 



1 Complementary ' kings and queens ' are also met with in this family. 



