72 ENTOMOLOGICAL NEWS. [May, 



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

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



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

 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 of 

 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 denote 

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

 imago, although formerly it was synonymous vi\\hpupa. Insects 

 with an incomplete transformation are Grasshoppers, Dragflies, etc. 



3. These insects undergo no transformatton, 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 on 

 the various orders. 



TJie principal characters which distinguish the Insecta from the 

 other classes of Arthropoda may be tabulated as follows (These 

 characters apply only to adult individuals) : 



Arthropoda. — Animals with a segmented body and jointed segmental 

 appendages. 



A. — Breathing by gills (Division Branchiata.) 

 Body usually divided into a cephalo-thorax and an abdomen; two pairs 

 of antennae Class I, Crustacea. 



B. — Breathing by tracheae (Division Tracheata.) 

 I. No true antennae (Subdivision Chelicerota.) 

 Body usually divided into a cephalo-thorax and an abdomen; four 

 pairs of thoracic feet; no abdominal feet. Class II, Arachnifla. 



