332 



General Biology 



When insects hatch from eggs (Fig. 241, I, II), and are unlike their 

 parent-forms, they are said to be heterometabolous ( ). 



Such insects hatch as nymphs ( ), a wingless form 



gradually growing larger and larger wings after each ecdysis until the 

 adult form is reached. Insects are holometabolous ( ) 



if there is a complete metamorphosis, such as being born a worm-like 

 larva ( ), which takes food for a short time and then 



TraSc 



fpiV 



HtTraSc 



215. 



A. Respiratory system of worker honey-bee as seen from above, one anterior 

 pair of abdominal sacs removed and transverse ventral commissures of abdomen 

 not shown. / sp, III sp, VII sp, spiracles; HtTraSc, Tra Sc, 1, 2, 4, 7, 8, 10, 

 tracheal sacs; Tra, tracheae. (From Snodgrass, Tech. Series 18, Bur. Ent., U. S. 

 Dep't of Agric.) 



B. A portion of the tracheal tissue of a cockroach, highly magnified. Only 

 parts of the tubes are in focus. 



cu., Cuticular lining with spiral thickening; nu., nuclei of the protoplasmic 

 layer; ppm., protoplasmic layer continuous with the epidermis ("hypodermis") of 

 the surface of the body. (After Borradaile.) 



goes into a resting or pupal stage during which no food is taken, and 

 during which time it loses all its larval structures, finally developing into 

 a complete adult insect, known then as an imago' ( ). 



In those cases where there is no metamorphosis, the animals are 

 said to be ametabolous ( ). 



