CHAPTER IV. 
Order Thysanura (Thys-a-nu'ra). 
Bristle-tails , Spring-tails , Fish-moths , and others . 
77z^ members of this order are wingless insects which 
undergo no metamorphosis , the larval form being retained by 
the adult . The mandibles and maxillce are retracted within 
the cavity of the head, so that only their tips are visible; they 
have , however , freedom of motion , * 72 /* be used for 
biting and chewing soft substances. True compound eyes are 
rarely present; but in some genera there is a group of simple 
eyes on each side of the head\ The abdomen is sometimes 
furnished with rudimentary legs . 
Under stones and decayed leaves and wood, in the chinks 
of bark, amongmoss, in damp 
places, on snow or on pools, 
or sometimes in houses, are 
the members of this order to 
be found. They are for the 
most part very small insects, 
but sometimes they are nu¬ 
merous and lively enough to 
make up for their lack in 
size. They have no wings, 
^-3 but they can either run very 
mobryidee. (Drawn by J. M. Stedman, f^St 0 T jump Very far. Their 
under the author’s direction.) 8 , labrum; . 1 „ 
10, mandible; n, maxilla: 12, labium; 12 d, mouth-parts are USUally fit- 
labial palpus. ’ , , , . . . J 
ted for biting, but are very 
difficult to study, because they are retracted within the 
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