Metamorphosis 



117 



insect in form and differing only in the absence of 

 wings. A Dragonfly or a Mayfly begins free life as 

 an aquatic larva, not resembling its parents ; after 

 a few moults this becomes a nymph, showing an 

 approach to the body-form of the imago and bearing 

 rudimentary wings. The off^spring of a Cicad (see 

 fig. 86) is a burrowing grub (fig. 74), provided 

 with strong, digging fore-legs, and very unlike its 

 parent in appearance. During a long underground 

 life, it under- 

 goes successive 

 moults and 

 obtains the 

 rudiments of 

 wings ; during 

 the stage pre- 

 vious to the 

 emergence of 

 the imago it 

 ceases to feed 

 and remains 

 quiescent with- 

 in an earthen 

 cell (fig. 75), 



thus showing Fig. 75.— Earthen cells formed by Cicad Nymphs, a. 



somp annrmrh elevation; ^. section ; c. passive nymph waiting final 



avjuic appiuacii moult; d. mature nymph ready to undergo change 



to the niiml ^"d emerge through opening e. From Marlatt (after 



, , . F " F''^ Riley), Bull. 14 (n.s.) Div. Ent. U.S. Dept. Agr. 



habit though 



no pupal form is assumed. In the tiny black insects 

 known as Thrips (often found abundantly on flower- 

 heads) the nymph in its last stage, though it moves, 

 is sluggish ; its limbs are enveloped in a membrane 

 and its wings enclosed in sheaths. The Scale-insects 

 furnish a specially interesting transition stage. While 

 the females undergo a typically incomplete metamor- 

 phosis, the males (see fig. no) pass the ante-imaginal 



