36 



ECONOMIC ENTOMOLOGY 



and segmentation of the body; (4) in the development of feelers and 

 mouth-parts, (5) in the number and development of organs of locomotion 

 and (6) in the alimentary, tracheal and nervous systems. Examples 

 can be readily found to illustrate the differences outlined above. 



Pupal Stage. — After a short period of rest the full-grown larva of 

 holometabolic forms changes to a pupa within a pupal skin. Usually 

 the outer skin is shed, but sometimes, as in the Diptera, the outer skin 

 becomes a puparium. During the pupal stage not only are all the 



Fig. 39. — Types of pupae, i. Asparagus beetle (free); 2, puparium of cabbage 

 root maggot (coarctate); 3, bud moth (obtect); 4, tobacco sphinx (obtect); 5, male 

 of maple scale (free). 



external organs of the adult insect formed, but even the internal organs 

 undergo profound changes. The organs break down and reform, and 

 the structures are adapted to the new creature with its new mode of life. 



In most insects the pupa is quiescent but it is quite active in the 

 Culicidae and other families. There is but little difference, except 

 the presence of rudimentary wings, between the larval and pupal 

 stages of the insects belonging to the Hemiptera and the Orthoptera. 



Three types of pupae are recognized (Fig. 39): (i) ohtect, where the 

 appendages and body are closely united, as in Lepidoptera and some 

 Coleoptera; (2) free, where the appendages are free, as in Neuroptera, 



