INSECT TRANSFORMATION 



thorax are plainly visible, having grown out from those 

 segments beneath the cuticle of the preceding instar before 

 the moult took place. These wing-rudiments are, at this 

 stage, merely rounded lobes on the hind dorsal region of the 

 segments to which they belong, traversed by diverging track- 

 lines which indicate the position of air-tubes marking out 

 generally the course of the future wing-nervures. 



a 



FIG. ig. SUCCESSIVE STAGES IN THE GROWTH OF A GRASSHOPPER (MddnOplus). 



a, first instar ; b, second instar ; c, third instar with minute wing-rudiments ; d, e, fourth and 

 fifth instars with distinct wing-rudiments. Magnified (natural size indicated in each case by the 

 index lines). /, Adult. Natural size. From Comstock, "Introduction to Entomology ", after 

 Emertonj 



With the assumption of the cuticle of the fourth stage 

 (Fig. 19 d), the wing-rudiments are seen to be much more 

 prominent than before, no longer mere lobes on the mesothorax 

 and metathorax, but imperfectly jointed to those segments, 

 looking like miniature wings with the developing nervuration 

 distinctly visible. The general form of the fifth instar (Fig. 

 19 e) closely resembles that of the fourth, but the wing- 



