GROWTH AND TRANSFORMATION 163 



described, the young insect, all through its growth in 

 general aspect, and indeed in many details of structure, 

 resembles the adult, and its wing- rudiments appear at an 

 early stage as outgrowths of the two thoracic segments that 

 carry the wings. Such insects undergo no marked trans- 

 formation ; a young grasshopper has the long leaping legs, 

 and a young cockroach the flattened body and rounded 



Fig. 42. — Forms of Vine Aphid {M acrosiphum vittcola) , Amenca . 

 A, newborn young, X 70 ; B, nymph with wing-rudiments, X 20; 

 C, winged virgin female, X 25 ; D, adult wingless female, X 35. 

 After A. C. Baker (jfotdrn. Agric, Res. U.S.D.A. xi, 1917). 



pronotum of their respective parents. In a study of the 

 biology of insects it is noteworthy that the similarity of 

 form between adult and young goes along with the similarity 

 in the mode of life ; young cockroaches in various stages of 

 growth may be found along with adults sheltering in cracks 

 of walls or lurking beneath hot-water pipes in houses, while 

 young grasshoppers and locusts walk or leap among herbage 



