INSECTA 393 







METAMORPHOSIS. This is a gradual process (insecta hemimetabola) in the 

 Rhynchota and Orthoptera, or a sudden one with a stage of inanition 

 (insecta metabola) in the other orders. This stage of rest or inanition, 

 the PUPA, concludes the larval life (caterpillar, maggot, &c.) ; during the 

 pupal stage no nourishment at all is taken, but the internal organs undergo 

 changes ; in some forms the rest is not absolute, as voluntary local move- 

 ments may take place (pupae of gnats). 



The insects are divided into numerous orders according to the form of 

 the mouth parts, the structure of the wings, as well as the manner of the 

 development ; with the exception of the lowest group (Apterygota\ which 

 is most nearly related to the ancestors of the insects, and which has 

 no wings and undergoes no metamorphosis, all the remaining orders, which 

 are termed Pterygota, have wings on the thorax, though there are, of 

 course, a few species and families of this order which have secondarily lost 

 their wings. 



The Pterygota include : 



(1) Orthoptera. Biting mouth parts, anterior wings leathery, posterior 



wings thin, folded longitudinally ; metamorphosis incomplete 

 (Grasshoppers, Crickets, Cockroaches). 



(2) Pseudoneuroptera. Biting mouth parts, wings of equal size, thin, 



not folded up (Dragon-flies, Hair and Feather Lice, Termites). 



(3) Rhynchota or Hemiptera. Mouth parts formed for puncturing and 



sucking ; wings alike, or the anterior wings may be thickened, 

 parchment-like (Plant-lice, Cicadae, Bugs and True Lice). 



(4) Neuroptera. Biting mouth parts ; wings alike, thin ; metamorphosis 



complete (Ant-Lions, Lace- Wing-Flies, &c.). 



(5) Trichoptera. Licking mouth parts ; anterior wings narrow, pos- 



terior wings longitudinally folded, both ornamented with little 

 hairs : the larvae are worm-like in form, live in water, and 

 breathe through tracheal gills (May-flies, &c.). 



(6) Lepidoptera. Suctorial mouth parts ; wings covered with scales 



(Butterflies). 



(7) Coleoptera. Biting mouth parts ; anterior wings thickened ; they 



differ in colour, appearance and function from the thin, folded 

 posterior wings (Beetles). 



(8) Hymenoptera. Mouth parts for licking or biting : the wings alike, 



membranous (Ichneumon flies, Ants, Wasps, Bees, Humble Bees). 



(9) Diptera. Mouth parts formed lor puncturing, sucking or licking ; 



posterior wings degenerated (Gnats, Flies, Gadflies, Fleas.) 

 (10) Strepsiptera . Anterior wings shortened : the femak; without wings 



and living parasitically (Fan-wings). 



The parasites of man occur amongst the Rhynchota, Coleop- 

 tera, and amongst the Diptera. 



[The most usual and recent classification of the Hexapoda is the 

 following : 



(1) Aptera. Wingless insects ; scarcely any metamorphosis. 



(2) Neuroptera. Four membranous wings, frequently with much net- 



work ; the front pair not much, if at all, harder than the under 

 pair; the latter with but little or no fan-like action in closing; 

 mandibulate ; metamorphosis variable, but rarely complete. 



