78 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 37 



hind wing lodges in this socket, securely locking the tegmen in such 

 a way that it cannot be displaced outward unless it is first slightly 

 moved toward the midline of the body and then raised vertically in 

 order to dislodge the mesal edge of the second axillary sclerite of the 

 hind wing from the tegminal socket. The site of this socket near the 

 base of the first anal vein of the tegmen is noticeable from the upper 

 surface as a slightly raised, dark-colored spot. The inferior surface 

 of the basal part of the anal region of the fore wing is covered with 

 spinose hairs which are similar in appearance to those on the tubercles 

 of the prescutal mesothoracic areas and the third axillary sclerites. 



The writer believes that the locking apparatus of the fore wing has 

 not been hitherto described. It seems, however, that this structure 

 can be found in other grasshoppers too, since he has observed it in 

 species of the genus Dichroplus (Catantopinae). In this last genus, 

 however, it does not seem so well developed as in Marellia. 



V. THE LEGS 



The fore and middle legs of Marellia rcmipcs (fig. 12) are similar 

 to those of other grasshoppers. Their femora are somewhat more 

 robust in the male (not figured) than in the female. 



A noticeable feature in all the legs of Marellia is the poor develop- 

 ment of the pretarsal arolia (figs. 12, 13, 14, Ar). In spite of its 

 being a phytophilous form, the arolia are not developed as usual in 

 the plant-dwelling grasshoppers, but instead are reduced as in the ge- 

 ophilous forms. The fact that the host plants of this genus have float- 

 ing leaves that lie in a horizontal position, which makes climbing 

 unnecessary, might be related to the poor development of the arolia. 

 It has already been noted that this feature may possibly indicate a 

 relationship with the geophilous Ommexechidae. 



The hind legs. — The hind legs of Marellia (fig. 13) are remarkable 

 in several respects and, with the probable exception of the ovipositor, 

 they are the organs of this insect that show the more advanced ana- 

 tomical adaptations to the semiaquatic habitat. 



The coxae (fig. 13, Cx) are similar to those of other grasshoppers, 

 being globose, somewhat elongated, and articulated to the thorax by 

 means of a relatively small trochantin (fig. 8, Tn). The hind femora 

 (fig. 13, Fm) are unusually robust. In fact, the great development of 

 the hind femora is one of the distinctive features in the general aspect 

 of this grasshopper. Aquatic locomotion, it seems, calls for unusual 

 strength of the tibial muscles lodged in the hind femur. The lateral ex- 

 ternal surfaces of the hind femora are marked with the usual fish-bone 



