300 ARTICULATA: INSECTA. 



But there are some kinds of insects which do not ap- 

 parently pass through all the changes enumerated above, 

 but whose larvae pass by insensible gradations to the pupa 

 state, and from the latter to the perfect insects, all the 

 Avhile remaining in a state of activity. These are said to 

 undergo only & partial transformation. 



The grasshopper, for example, is hatched from the egg as a wingless 

 insect. It eats voraciously, grows rapidly, hops about without the 

 use of wings, sheds its skin more or less regularly, and appears after 

 each shedding with longer wings and more completely developed 

 limbs, until at length it ceases to grow, and then, shedding the skin 

 for the last time, comes forth an imago or adult grasshopper. 



The larvre of those insects which undergo only a par- 

 tial transformation have only six legs, the same as adult 

 insects. Of the larvae which undergo a complete trans- 

 formation, some kinds, as maggots, have no legs ; others 

 FIG 379 have a pair of legs to each of the three 



first segments ; others have a pair to each 

 of the three first segments, and, besides 

 these, several fleshy legs placed beneath 

 the abdominal segments, and known as 



" Measure-worm " . 



Larva of a Geomet- pl'Op-legS. 



rid Moth, with two Insects proper may be divided into 



pair of prop-legs. o " .. 



seven groups or bub-orders, thus : 



1. HYMEXOPTERA or Membrane-winged Insects ; with four mem- 

 branous wings traversed by a few irregularly branching veins ; 

 four jaws, the upper pair horny, and the lower longer and 

 softer ; as Bees, Wasps, Ichneumons, Saw-flies, etc. 



'2. LEPIDOPTERA or Scaly- winged Insects ; with four wings cov- 

 ered with scales which are easily removed ; and with a tongue 

 formed of two grooved threads placed side by side so as to 

 make a sucking organ ; as Butterflies and Moths. 



3. DlPTERA or Two-winged Insects ; with only two real wings, the 

 hind pair being represented by two knobbed threads or baU 



