362 



THE ANATOMY OF INVERTEBRATED ANIMALS. 



gnathites are changed in form and function, or become con- 

 fluent. 



Tiie insects which, in this view of their morphological re- 



Pio. 102.— Camiwdea staphy'inus, one of the 7Vii/sanura (after Luhbock).^ 



lations, occupy the lowest position in the group, are the Col- 

 lembola and ThysiDiura^ the Mallophaga^ and the Pedlcu- 

 llna, inasmuch as they possess no trace of wings and undergo 

 no metamorphosis. 



The CoUemhoIa and Thyscmura undergo no metamorpho- 

 sis, and are always wingless. The abdomen contains six seg- 

 ments only in the Collemhola (Podura^ Smynfhurus, Tomo- 

 ceros), in which group the mouth is usually provided with 

 mandibles and maxilL'B, though these, instead of being artic- 

 ulated with the sides of the head, are capable of being re- 



tracted into its interior.' 

 suctorial. 



In the crenus Anoma the mouth is 



1 " Monocfraph on the Collembola and Thysanura!;'' pi. liii. 



