72 ENTOMOLOGICAL NEWS. [M.iy. 



2. Insects which pass through three states, viz.. f i) the . 

 (2) the Nymph and (3) the Imago. 



3. Insects which pass through two states, viz., (i) the E 

 and (2) the Larva-form. 



1. Insects passing through four such states differ very much 

 when in their larval state from the form which they possess when 

 in their imago state, and hence are said to undergo a complete 

 metamorphosis or transformation. Such are Bees, Butterflies, 

 Beetles, etc. Very frequently the pupa is enclosed in a cocoon <>t 

 silk, earth, chips, or other substance. 



2. In other insects there is no distinction between the larval and 

 pupal states, and the larva much resembles the imago, although 

 differing noticeably by the wings being not yet developed as or- 

 gans of flight. Such insects pass through an incomplete trans- 

 formation. Lately the word Nymph has been used to dente 

 that state of existence in such insects between the egg and the 

 imago, although formerly it was synonymous with pupa. Insects 

 with an incomplete transformation are Grasshoppers, Dragflies, etc. 



3. These insects undergo no transformation, the larval form 

 being retained to the end of their existence. Such are Fish- 

 moths and Spring-tails. 



The growth of an insect is completed in its larval or its nymph 

 state, and however long an insect may live, it never increases in 

 size after it has attained its perfect form. The modes of passing 

 through the successive changes of form vary much in the different 

 orders of insects, and are always full of interest to careful ob- 

 servers. These changes will be referred to in future articles .m 

 the various orders. 



I 



The principal characters which distinguish the Insecta from tin- 

 other classes of Arthropoda may be tabulated as follows (Th< -< 

 characters apply only to adult individuals): 



Arthropoda. Animals with a segmented body and jointed M--iiK-m.il 



appendages. 



A. Breathing by gills i 1 >i\isi.m Uraiu'liiatd.^ 



I'.' >dy usually divided into a ceplialo-thorax and an al>doim-u ; two pairs 

 of antenna- . . Qass 1, Crustacea. 



B. breathing by tracln-.r il>i\ision Ti\ichcata.\ 

 i. No true antenna- > Subdivision Ckelicerota.} 



Body usually divided into a eephalo-lliorax and an abdomen; tour 

 pairs of thoraric feet; no abdominal feet. I'las-. II. Aracllllitla. 



