TRIDACTYLIDES 



337 



their habits, the body being contracted in the middle in such a 

 way as to permit the middle and hind legs to be packed against 

 it, so that the cylindrical form is not interfered with by these 

 appendages while the excavating anterior legs are at work in 

 front of the Insect. The abdomen has nine segments ; the 

 terminal one, said to be remarkably long and destitute of cerci, 

 is not shown in our figure. 



The genus Tridactylus is considered by de Saussure to form, 

 with its ally Rhipipteryx, a division of Gryllotalpinae, but they 

 are treated, perhaps more 

 correctly, by Brurmer as a 

 separate tribe. T. varie- 

 gatus (Fig. 209) is a small 

 Insect, abundant in sandy 

 places on the banks of 

 rivers in Southern Europe, 

 extending on the Khone 

 as far north as Geneva, 

 and is remarkable for its 

 great power of leaping, and 

 for the rapidity with which 

 it can burrow in the sand. 

 This anomalous Insect has 

 only ten joints to the an- 

 tennae. Its alar organs 

 are imperfect, and not like 

 those of other Gryllidae in either form or neuration. The hind 

 legs are of peculiar structure, the tibiae terminating in two pro- 

 cesses between which is situate a rudimentary tarsus. Near the 

 extremity of the tibia there are some plates, forming two series, 

 that can be adpressed to the tibia, or extended as shown in our 

 figure. The body is terminated by four rather short, very 

 mobile processes ; the upper pair of these are each two-jointed, 

 and are thought by de Saussure and Haase l to be cerci ; the 

 inferior pair, being articulated processes of the anal segment, 

 their presence in addition to cerci is remarkable. It is difficult 

 to distinguish the sexes of this Insect. 



The exotic genus Rhipipteryx is allied to Tridactylus. It is 

 widely distributed in South America, but the little Insects that 



1 Morph. Jalirb. xv. 1889, p. 400. 

 VOL. V Z 



FIG. 209. Tridactylus wriegatus, France. 



