ANATOMY OF MARELLIA REMIPES — CARBONELL 



8i 



able upward (see fig. 13 B) so that the spurs probably act to avoid 

 slipping on the smooth surface of the leaves w^hen the insect jumps 

 from them. 



An expanded distal portion of the hind tibiae is not an uncommon 

 feature among semiaquatic orthopterans. It can be observed in 

 the Tetrigidae and in other grasshoppers of semiaquatic habits, such 

 as Cornops aquaticiim (Covelo de Zolessi, 1956) and others. The 

 hind tibiae of Marellia remipes seem, however, to be the most per- 

 fected swimming organs among the true acridoid grasshoppers, being 

 supplemented in their function by the tarsi, as described immediately 

 below. 



Ar Un 



Fig. 14. — Tarsus of the right hind leg of Marellia remipes. 



A, dorsal view. B, lateral (external or anterior) view. C, mesa! (internal or 

 posterior) view. 



Ar, arolium ; ce, external edge of first tarsomere; ie, internal edge of same; 

 iTar, ^Tar, sTar, first, second, and third tarsomeres ; TP, tarsal pulvilli ; Un, 

 claws. 



The hind tarsi. — The hind tarsus of Marellia (fig. 13, Tar, fig. 14) 

 presents a striking form, being indeed highly modified in relation to 

 the function of swimming. The first and third tarsomeres (fig. 14, 

 iTar, sTar) are expanded and, when the tarsus is extended as for 

 swimming, the tibial spurs support the first tarsomere from behind 

 (see fig. 13 C). 



The first tarsomere is the largest of the three. Its margins are ex- 

 panded and upcurved, especially the inner one. The whole first tar- 

 somere is affected by a helical torsion (Rosas-Costa, 1940), and from 

 a nearly horizontal plane in its basal portion it turns inward to an 

 almost vertical position in its distal part. The inferior surface of this 



