GENERAL REMARKS. 



The mode of development in all of the first series 

 of orders from I.-IX. is as a rule direct, and this neces- 

 sarily unites the Thysanuriform larva, when it is pres- 

 ent, more or less closely with the adult stages, and 

 the adults are apt to show traces of this connection 

 in the retention of certain primitive characteristics. 

 The absence of a waist or deep constriction between 

 the thorax and the abdomen is due to the fact that 

 the junction with the metathorax remains in most 

 adults as it is in the larva and in Thysanura. The 

 mouth parts also are for biting, except in the highly 

 specialized Hemiptera, in which, although the suc- 

 torial characteristics of these parts are developed early, 

 the larvae, with this exception, have what may be 

 called a Thysanuriform stage. The highly specialized 

 adults of groups having indirect development (Coc- 

 cidse) are not exceptions to this rule, and retain to a 

 recognizable degree the primitive form of the larvae. 



The second series of orders from X.-XVI. have, as 

 a rule, more complicated modes of development, intro- 

 ducing various intermediate and often extraordinary 

 stages, such as grubs, caterpillars, etc. Following 

 Brauer and some other entomologists, we have re- 

 garded these as more or less degraded modifications 

 of the primitive Thysanuriform larva, but have spoken 



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