324- MOTIONS OF INSECTS. 



assist the insects that have them in their caps; and 

 when they climb they may in some degree act as suckers, 

 and prevent them from falling. But their use will be 

 best ascertained by a review of the principal genera of 

 the order. Of these the cock-roaches (Blatta), the 

 spectres (Phasma), and the praying insects (Mantis\ are 

 distinguished by tarsi of five joints a . The grasshoppers 

 with setaceous antennae (Acrida] have four tarsal joints. 

 Those with filiform antennae (Locusta and Acryd.ium\ 

 those with ensiform (Truxalis b ), and the crickets (Gryl- 

 lm\ have only three. In Blatta^ the variations with 

 respect to the suckers and cushions (for many species 

 are furnished with both) are remarkable. The former 

 in some (Blatta giganted) are altogether wanting; in 

 others (B. Petiveriana) they are mere rudiments ; and 

 in others (B. Maderte) they are more conspicuous, and 

 resemble those of the Gryllidce. The foot-cushions 

 also in some are nearly obselete, and occupy the mere 

 extremity of the four first tarsal joints (B. orientalis, 

 americana, capensis, &c.). In B. Petivcriana there is 

 none upon the first joint ; but upon the extremity of 

 the four last, not excepting the claw-joint, there is a 

 minute orbicular concave one, resembling a sucker. In 

 others (B. gigantea, &c.) they extend the length of the 

 four first joints, and are very conspicuous. In some 



* In a specimen in my cabinet of Blatta gigantea, the posterior 

 and anterior tarsi of one side have only four joints, while the inter- 

 mediate one has five. On the other side the hind leg is broken off, 

 but the anterior and intermediate tarsi have both five joints. In 

 another specimen one posterior tarsus has four and the other five 

 joints. 



b The name of this genus properly spelled is Troxallis, from the 

 Greek T^%xMis, Gryllus. 



