THE INSECTS OF NEW JERSEY. 23 



use in tucking in the elaborately folded hind wings beneath the 

 short wing-covers. The transformations are incomplete. 



The Colcoptera, or sheath-winged insects, commonly called 

 beetles, illustrate the extreme of this line of development. They 

 have the fore wings hardened so as to- be useless for purposes of 

 flight, and they are laid on the back so as to meet in a straight 

 line down the middle. The secondaries are folded transversely 

 under the wing-covers or elytra, and the metamorphosis is com- 

 plete. 



The third and last of the mandibulate series is that in which 

 all the thoracic rings are united together to form a more or less 

 compact or even, barrel-shaped mass. The head is now free from 

 the thorax and united to it only by a slender neck. A fly, a bee 

 or a butterrlv will serve as an illustration. 



The ancestry of this series began in the aquatic forms passing 

 the larval stages under water, and the Hphemerida or day-flies are 

 the earliest types. The larvae live in the mud of stream and other 

 water bodies in immense numbers and, when full grown, change 

 to frail, gossamer-'winged flies which have the fore wings larger 

 than the second pair and both pairs held upright like those of 

 butterflies when at rest. Most of the species have slender anal 

 filaments, the mouth parts are aborted and the life period is very 

 short in the adult stage, though as larvae they may live for years. 

 The transformations are incomplete. 



The Odonata or dragon flies are also aquatic in the larval stage 

 and in their day were numerous and well developed. They have 

 two pairs of flat, net-veined, similar wings, and they are predatory 

 in habit. The larvae live in the mud of ponds and among water 

 plants, feeding upon any soft-bodied insects that come in their 

 way, and the pupa is as active as the larva. The order has many 

 structural peculiarities in all stages and 'has no descendants, the 

 line now tending to become lost. 



From the Ephemerid type two lines diverged in larval struc- 

 ture one to a caterpillar-like larva living in mud and moist 

 places generally, the other toward a similar larva living in 

 water and building a tube or case for protection. The latter are 

 known as Trichoptera or "caddice-flies," the larvae either preda- 

 tory or plant-feeding. The adults have the wings more or less 



