OF THE STATE ENTOMOLOGIST. 



4 — Radiata or Star Animals. These have the body arranged on 

 the plan of an asterisk (*), radiating from a common center. They 

 are often called Zoophytes, and comprise the very lowest animals — 

 some of which, as the sponges, corals, etc., were for a long time con- 

 sidered plants, and do, indeed, connect the Animal and the Vegetal 

 Kingdoms. 



With the exception of a few Molluscous snails and slugs, the ani- 

 iiials of the last two Branches live 'almost entirely in water, and we 

 see that an Insect belongs to the second great Branch, and that it 

 shares the jointed or articulate structure in common with the other 

 animals of that Branch. Wherein;, then, does it differ from them? 

 Briefly, in having only 13 joints to the body,* including the head as a 

 joint, and in the adult stage 6 true, jointed legs, and usually (not 

 always) wings. The five classes of Articulates differ from each other 

 in the number of legs they possess jn the adult form, as follows: 

 Insecta^Q legs; Arachnida^S; Crustacea, 10-14; 3I>/riaj)oda^ more 

 than 14 ; Annelida, none. 



I say true legs and in the adult form, because there are some 

 mites (Class A7'acJmida) which, when young, have six legs only, while 

 many insects have additional legs in their preparatory or adolescent 

 stages, which are not jointed, but membranous, and are lost in the 

 perfect stage: these are called false, sham, or prolegs. 



Insects are further characterized by having the body divided into 

 three distinct parts : the 7iead, which bears the sense organs ; the 

 thoraX) which bears the organs of locomotion; and the ahdomen, 

 which bears the reproductive organs. They also undergo a series of 

 molts, and exist in four distinct stages : 1st, the e(/ff stage ; 2nd, the 

 larva (meaning masked — the future and ultimate form being usually 

 masked or hidden, so far as external appearance goes) or active stage ; 

 Srd, the pupa (sometimes called chrysalis or nymph) or usually quies- 

 cent stage ; 4th, the imago or perfect stage, in which alone the wings 

 appear. To be brief, then, I would give the following definition of an 

 Insect: A 13 jointed, ^legged animal, with an external sheleton ; 

 undergoing transformations or metamorphoses, and hreaihing through 

 spiracles {hreathing holes) which lead to tracheae {air tuhes): the hody^ 

 in the adult divided into three distinct parts (Jiead, thorax and ah- 

 domen)', with or without wing s.\ 



*An additional sulyoint is often apparent, and sometimes very fully developed, as, for instance, 

 in the larva of Passalus cornutus (4th Rep., Fig. 6'2, a) . 



I I fancy the exclamation from some curious reader — ' ' Well, Avhy , if the possession of IS joints 

 and 6 articulate legs be so true a test of an insect, do some authors include the spiders and tliousand- 

 legged worms in the same Class and call them insects ? Does not Packard in his 'Guide to the Study of 

 Insects' give us in his first figure a 21-jointed larva as typical of the Class, and does he not give us three 

 Orders in tlie Class, elevating i\ie. ArachnidatmA Myriapoda to the same rank as Insecta; and has not this 

 arrangement the sanction of such eminent men as Agassiz and Dana ?' ' It is true, there is some dis- 

 pute as to how many typical joints the head of insects is composed of, Packard himself arriving at 

 different conclusions in the first and third editions of his work ; while the figure referred to might con- 

 vey the impression above expressed. But all the discussion on the first |head is more or less hypothe- 

 tical, and the larva represented by the figure referred to is only apparently 21-jointed, being that of 



