THE INSECTS OF NEW JERSEY. 19 



CHAPTER II. 



The system used in this list is practically the same as that of 

 the previous edition, and it may be well to briefly state the char- 

 acters of the orders as used here. 



I assume that the primitive insect from which all the types now 

 existing have descended was a small, soft-bodied creature living 

 in moist earth or mud along the banks of bodies of water. It had 

 six true legs, and probably leg-like abdominal appendages, no 

 wings, no compound eyes or no eyes at all, and no developed 

 breathing system ; taking in oxygen from the surrounding 

 moisture through all parts of the skin surface. The head was 

 not much differentiated from the rest of the body, and the mouth 

 parts were generalized, with three or four pairs of fleshy processes 

 from which the jointed and other appendages of the more 

 specialized mouth structures developed. These were the Proto- 

 thysanura, and creatures not so very different occur among the 

 TJiysanura of the present day. The latter, however, have in some 

 cases well developed mouth parts, while many live in dry places 

 and have a fairly complete trachea! system. There are no distinct 

 metamorphoses and the insects are wingless throughout. 



Our primitive Thysanurans divided early into two branches 

 on mouth structure; some becoming mandibulate or fitted for 

 chewing, while others became haustellate, fitted for puncturing 

 plant or animal cells, and living on the juices alone. In both 

 these branches wings developed, very different in type and yet 

 with fundamentally the same scheme of venation. 



The little order Thysanoptera has the mouth parts fitted for 

 puncturing or scraping the surface so as to get at the plant juices, 

 which are then drawn into the body. The wings are long, very 

 narrow, frail, not connected, and altogether the structure is 

 primitive. Popularly they are known as Thrips, and some of 

 them are decidedly injurious to farm crops. 



A decided step forward is made in the Rhyngota, in which the 

 mouth parts are developed into slender lancets fitted for piercing, 

 and are protected by a jointed beak except in the parasitica and 



