104 ARTHROPOD A. 



(only wanting the wings, or the wings only partially developed), 

 or it may have no resemblance to it. 



Agamic reproduction (parthenogenesis) occurs in some of the 

 orders, chiefly among the Hemiptera and Hymenoptera ; this is 

 said to be the result of cell-formation, " comparable to a kind of 

 budding." 



The life of an insect for good or for evil, with a few exceptions, 

 is in its larval stage ; in its perfect state its life is short, some- 

 times lasting only a few hours. In the fertilization of plants 

 insects play an important part by conveying the pollen from the 

 anthers to the stigma. 



Insects and their allies are supposed by Herbert Spencer to 

 be compound animals, each one representing as many individuals 

 as there are true segments, but which have become severally spe- 

 cialized for certain definite functions. 



Considering the Mallophaga to be degraded forms of Hemiptera, 

 and that the Trichoptera are not more entitled to ordinal rank 

 than other groups of Neuroptera, there will remain nine orders 

 which, if we except Collembola and Thysanura, are universally 

 admitted. To these are sometimes added Thysanoptera [aberrant 

 Hemiptera], Euplexoptera [an isolated form of Orthoptera], 

 Aphaniptera [degraded Diptera], and Strepsiptera and Achri- 

 optera [abnormal Coleoptera]. 



Apterous : no metamorphosis (Arnetabola). 



Abdomen with terminal saltatory appendages. . . COLLEMBOLA. 



Abdomen without such appendages THYSANUKA. 



Winged : metamorphosis in nearly all. 



Metamorphosis incomplete (Hemimetabola, Ho- 

 momorpha). 



Without mandibles [suctorial] HEMIPTERA. 



With mandibles. 



Wings dissimilar in texture ORTHOPTERA. 



Wings similar in texture NEUROPTERA. 



Metamorphosis complete (Metabola, Hetero- 



morpha). 

 Without mandibles. 



Two wings DIPTERA. 



Four wings LEPIDOPTERA. 



With mandibles. 



Upper wing coriaceous COLEOPTERA. 



Upper and. lower wings membranous HYMENOPTERA. 



After the Collembola and Thysanura, the Hemiptera contain 



