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branches, the Bythoscopidas being in some respects extremely 

 specialized, while the Jassidas are subdivided into nearly equal 

 branches, Jassinae and Tettigoninae. The relations of all these 

 groups can be expressed in the following diagram : 



The Heteroptera have in like manner been arranged more with 

 reference to convenience than upon a phylogenetic basis, the 

 strictly aquatic forms being made to occupy the lowest position, 

 and the series passing from these to the semi-aquatic, littoral, 

 terrestrial, and arboreal a plan which does not seem to me to 

 correspond in any sense with the probable line of descent. It ap 

 pears evident, even upon a very hasty examination of the group, 

 that the aquatic forms are descendants of non-aquatic forms and 

 that the derivation of the non-aquatic and terrestrial forms from 

 the aquatic groups is out of the question. Not only does the 

 structure of the groups oppose such an idea, but, on any theory 

 of the origin of the Hemiptera from the simpler groups of insects, 

 we must assume that they connect with the non-aquatic groups. 

 It is only necessary to mention the specialized condition of the 

 antennae in the whole series of Cryptocerata and the extremely 

 specialized mouth-parts of Corisidas to show the nature of the 

 morphological evidence, and to attempt to find a generalized 

 aquatic ancestral form, to see the force of the latter argument. 

 It may be in place to call attention further to the general fact that 

 all aquatic insects are such by secondary adaptation and trace 

 their ancestry to terrestrial forms, just as certainly, I believe, as 

 that all aquatic mammalia, such as whales, seals, &c., trace their 

 ancestry to terrestrial forms. 



The more probable line of descent is that the strictly aquatic 

 forms are descended from semi-aquatic forms, and these from 

 non-aquatic or littoral species, and in some such generalized form 

 as may be represented now by the Saldidas we may find the stock 



