64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I37 



species of MarelUa the specific name of rcniipes, or oar-shaped legs. 

 The unusual structure of the ovipositor has for a long time been re- 

 garded as a further anatomical adaptation to the aquatic habitat, 

 though it was not until recently (Carbonell, 1957) that the meaning 

 of this modification of the egg-laying organ was ascertained. Even 

 more striking than these structural adaptations are, in the writer's 

 opinion, the corresponding adaptations in behavior, such as the habit 

 of swimming under water and the very peculiar oviposition habits. 



The study of the external anatomy of MarelUa remipes has made 

 evident to the writer that the aforementioned adaptations are not the 

 only ones to be found in this remarkable insect, which is also struc- 

 turally modified for its life on the horizontal surface of the floating 

 leaves of the host plants, and for feeding on them from their upper 

 surfaces. Though a phytophilous grasshopper in the strict sense of 

 the word, the general depressed shape of its body, the position of its 

 eyes on the upper part of the head, and the reduction of its pretarsal 

 arolia are features characteristic of the geophilous forms. This may 

 be interpreted as a convergence produced by the life upon a hori- 

 zontal surface, but if the Pauliniidae are phylogenetically related to 

 the Ommexechidae, as the study of the phallic complex of these fami- 

 lies has suggested to Dirsh (1956), then the presence of these features 

 in the Pauliniidae will not be just a case of convergence with the ge- 

 ophilous Ommexechidae, but will reveal instead, a community of an- 

 cestry. Paradoxically enough, the eminently geophilous and xero- 

 phyllic Ommexechidae would have their nearest relatives living in an 

 aquatic habitat, never coming to land except by accident. 



The fact that the immense majority of the Acridoidea are inhabit- 

 ants of dry land, and many of them distinctly xerophyllic, suggests 

 that the invasion of the aquatic habitat by a few species of them must 

 be a secondary event in the history of these insects. If the degree of 

 adaptive modifications to an unusual habitat attained by a certain spe- 

 cies can be considered as proportional to the length of time it has been 

 living in this particular habitat, then we are led by the study of the 

 external structure of the Pauliniidae to regard them as the representa- 

 tives of the earliest group of grasshoppers that made aquatic plants 

 their permanent abode. 



In the description of the external anatomy of Marellm remipes 

 that follows, the writer has borne in mind that the structure of several 

 species of grasshoppers has been described carefully and in great 

 detail, and therefore he has limited his account to the description of 

 those features of the insect that reveal adaptations to its habitat, or of 



