110 [Mny, 



foot. The genus Bhagovelia contaius at present eight or nine species, 

 and so far as I can discover none of the authors who have described 

 these species appear to have noticed the " wheel." The only reference 

 to it which I am able to find is an imperfect description in a short note 

 by Signoret* on the species of Bhar/o-dta khown to him, when he 

 writes of " un long appendice plumeux, ressemblant a une longue 

 plume de marabout, garantie par deux longs crochets courbes. Cette 

 piece n'est visible que lorsque I'inseete nage ; pour I'apercevoir, il faut 

 le laisser macerer et se ramollir pendant assez longtemps." 



Perhaps this last remark explains the failure of so many ob- 

 servers to notice the structure which to me seemed the most charac- 

 teristic feature in the insects I described. My specimens were pre- 

 served in spirit. Yet on examining a couple of dried Rhngovelia 

 infernalis, Butler, from Eodriguez in this Museum, I find that the 

 " wheel " is undoubtedly present, though, for the most part, folded 

 and drawn into the tarsal cleft. 



According to Mayr, Rhagovelia is characterized by the presence 

 of three segments in all the tarsi, the basal one in each foot being 

 exceedingly minute. At Mr. Champion's suggestion I have cleaned 

 and mounted in balsam a set of the legs of TrocJiopus. I find that in 

 the front foot there are two minute basal segments (not one only as I 

 described and figured). But the tarsi of the second and third legs 

 are undoubtedly two-segmented. The long proximal segment of the 

 second tarsus articulates directly with the tibia, there being no minute 

 basal segment as in Hhagovelia, while in the hind leg the foot consists 

 of a small basal and an elongate distal segment as shown in my fig. 6. 



It is possible that these distinctions, together with the characteristic 

 form of the body, the lateral insertion of the second and third legs 

 close together, and the shortened abdomen, may render-it advisable to 

 retain Trochopus as a distinct genus from Rhagovelia, its type being 

 T. 'plu'mbeus,'\^\i\.QV {=^ marinus, Carpenter). The "three prominent 

 spines " on the hind femora of Trochopus, to which I referred in my 

 description, are merely appendages of the cuticle situated on the outer 

 edge of the femur, as shown in my figure 1. There is, I now find, one 

 similar but much smaller spine at the distal end of the second femur. 



Prof. Uhler in his description refers to the portion of the thorax 

 which I called the " mesonotum," as the " posterior lobe of the pro- 

 notum." Comparing the specimens before me, not with Velia, but 

 with Hal abates, in which the prothorax is a narrow transverse segment 

 (the mesothorax being much elongated) f, I adopted a corresponding 



* Bull. Soc. Ent. Prance, 1877, p. Iv. 

 t F. Buchanan White, Pelagic Herniptera, in Rep. Voyage Challenger, Zoology, vol. vii. 



