460 MOTIONS OF INSECTS. 



particularly those of B, fascicularis. A Brazilian beetle in my cabinet, 

 belonging to the family of the Cleridce, but not arranging well under any of 

 Latreille's genera, which I have named Priocera variegata, has curious in- 

 voluted suckers on its feet. The strepsipterous genera Stylops and Xenos 

 are remarkable for the vesicles of membrane that cover the under side of 

 their tarsi, which, though flaccid in old specimens, appear to be inflated io 

 the living animal or those that are recent. 1 It is not improbable that these 

 vesicles, which are large and hairy, may act in some degree as suckers, 

 and assist it in climbing. 



The insects of the Orthoptera order are, many of them, remarkable for 

 two kinds of appendages connected with my present subject, being fur- 

 nished both with suckers and cushions. The former are concavo-convex 

 processes, varying in shape in different species, being sometimes orbicular, 

 sometimes ovate or oblong, and often wedge-shaped, which terminate the 

 tarsus between the claw, one on each foot. They are of a hard substance, 

 and seem capable of free motion. In some instances 2 , another minute 

 cavity is discoverable at the base of the concave part, similar to that in 

 Cimbex lutea. 3 The latter, the foot-cushions, are usually convex appen- 

 dages, of an oblong form, and often, though not always, divided in the 

 middle by a very deep longitudinal furrow, attached to the under side of 

 the tarsal joints. Sir E. Home is of opinion that the object of these foot- 

 cushions is to take off the jar when the body of the animal is suddenly 

 brought from a state of motion to a state of rest. 4 This may very likely 

 be one of their uses ; but there are several circumstances which militate 

 against its being the only one. By their elasticity they probably assist the 

 insects that have them in their leaps ; 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 pray- 

 ing insects (Mantis), are distinguished by tarsi of five joints. 5 The grass- 

 when it immediately began to rub the pulvilli against the tarsal brushes ; but on 

 replacing them on the glass they adhered as closely as before, and it was only by 

 efforts almost convulsive, and which seemed to threaten to pull off its limbs from 

 its body, that it could succeed in moving a quarter of an inch at a time. After 

 watching it with much interest for five minutes, it at last by its continued exertions 

 got its feet released and flew away, and alighted on a curtain, on which it walked 

 quite briskly, but soon again flew back to the window, where it had precisely the 

 same difficulty in pulling its pulvilli from the glass as before ; but after observing 

 it some time, and at last trying to catch it, that I might examine its feet with a 

 lens, it seemed by a vigorous effort to regain its powers, and ran quite actively on 

 the glass, and then flying away I lost sight of it. I am unable to give any satis- 

 factory solution of this singular fact. The season, and the fly's final activity, 

 preclude the idea of its arising from cold or debility, to which Mr. White attributes 

 the dragging of flies' legs at the close of autumn. The pulvilli certainly had much 

 more the appearance of adhering to the glass by a viscid material than by any 

 pressure of the atmosphere, and it is so far in favour of Mr. BlackwalPs hypothesis 

 on which one might conjecture that from some cause (perhaps of disease), the hairs 

 of the pulvilli had poured out a greater quantity of this viscid material than usual, 

 and more than the muscular strength of the fly was able to cope with. 



Kirby in Linn. Trans, xi. 106. t. viii. f. 13. a. 



I observed this in the hind legs of a variety of Locusta migratoria. 



Philos. Trans. 1816., 325. t. xix. f. 5. 



Ibid. p. 325. 



In a specimen in my cabinet of Blatta giyantea, the posterior and anterior tarsi 



