606 



GREBE. 



duced is quite distinct. In the house and field cricket 

 (see the article CIUCKET), which are very nearly 

 related to the grasshoppers, both forming, in tact, 

 portions of the genus Gryllus of Linmeus, we have 

 noticed the structure of the wing-covers, and in those 

 species of grasshoppers, which have long and slender 

 antenme, the structure is very similar. De Geer, 

 speaking of the great green Gryllus viridissimus, which 

 is common near London, thus describes the structure 

 as well as the mode in which the sound is produced : 

 " In that part of the right wing-cover of the male, 

 which is folded horizontally over the trunk, there is 

 a round plate, made of very fine transparent mem- 

 brane, resembling a little mirror or piece of talc, of the 

 tension of a drum. This membrane is surrounded by 

 a strong and prominent nervure, and is concealed 

 under the fold of the left wing-cover, which has also 

 several prominent nervures answering to the margin 

 of the nismbraae or ocellus. There is every reason 

 to believa that the brisk movement with which the 

 grasshopper rubs these nervures against each other, 

 produces a vibration in the membrane augmenting 

 the sound. The males in question sin? continually 

 in the hedges and trees during the months of July and 

 August, especially towards sunset and part of the 

 night. On approaching them they immediately cease 

 their song." But the majority of English grass- 

 hoppers belong to a distinct section, having short and 

 rather thick antennae (and belonging to the same 

 division as the locust), and in these the chirping is 

 produced in a different manner, the thighs being 

 rubbed alternately briskly against the closed wing- 

 covers, which causes the regular breaks in the chirp- 

 ing ; moreover, near the base of the hind legs, De 

 Geer discovered a cavity partially covered by mem- 

 brane, having a semi-circular aperture, which must 

 evidently contribute in a considerable degree to pro- 

 duce and augment the sound. 



The larva) and pupa) slates of these Insects are very 

 similar in form to that of the imago, 'the former being 

 destitute of wings, and the pupa) having only rudi- 

 mental wings and wing-covers ; hence, although in 

 these states they are able to leaf) to as great a distance 

 as when winged, they are incapable of chirping. 



GREBE (Podiceps). A genus of Palmipede, or 

 web-footed birds, belonging to Cuvier's family of 

 divers, or short-winged birds, and placed as the first 

 of that family in his arrangement. They are very 

 peculiar birds in their structure and habits, and on 

 that account they are highly interesting. They are, 

 in one respect, the first of the aquatic birds; but they 

 do not take up the connexion from the birds with 

 sentient bills, whereof the avocet is the last. Thev 

 take it up more from the herons, which find their 

 prey by wading in the shallows, and seizing it in the 

 free waters by means of a hard, firm, and sharp-pointed 

 bill, which they can use with great precision. 



The grebes seize the principal part of their food in 

 a similar manner, only they have the power of com- 

 mitting themselves to the water, and seizing the prey 

 when they are under the surface, and often at the 

 depth of a good many feet. For this purpose they are 

 admirably adapted, not only in the ibrm and action 

 of their organs of motion and prehension, but in the 

 general form of their bodies, and in the texture of the 

 feathers with which they are covered. 



As the grebes take up the character where it is lef 

 off by the herons and those other birds which, wading 

 but not swimming, capture their prey in the waters 



)y a firm bill directed with very certain aim, so they 

 ran?fer it to the sea divers properly so called, to 

 hose birds which subsist by following their prey 

 under the surface in the free range of the oceanic 

 A-aters. 



The grebes are not, however, sea birds, though 



hey can upon emergency make their way in salt 



water. They are inhabitants of the smaller lakes 



\nd ponds, especially those which are tangled with 



)lants ; and they are admirably fitted for making 



heir way under water in such places. We must, 



lowever, mention the generic characters before we 



>roceed farther with the general description. 



The bill is of mean length, though generally longer 

 than the head; it is straight, conical, and compressed 

 or cylindrical in its section. The upper mandible is 

 awl-shaped, and abruptly curved toward the point. 

 The nostrils are lateral, and pierced in the middle of 

 ihe length of the bill ; oblong and open externally, 

 but capable of being firmly closed internally by a 

 membrane ; and they have a communication the one 

 with the other. The feet are articulated far back- 

 wards ; the tarsi are very much compressed, and 

 have membranous margins. There are four toes on 

 each foot, three to the front and one to the rear; 

 these toes are margined by broad and very peculiar 

 membranes, which are, however, divided down nearly 

 to the articulations ; and it is on this account that 

 the name of Podiccps, or " divided foot," is given to 

 the genus. Of these toes the external one is the 

 longest ; and the fourth, or hind toe, is very com- 

 pressed, bordered with membrane, articulated rather 

 upon the inner side of the tarsus and touches with 

 the point only when the foot of the bird is on the 

 ground. 



From this form of the feet, their distance laterally 

 from each other, and the oblique motions of the joints 

 both of the tibiae and the tarsi, the grebes are very 

 clumsy and imperfect walkers. Their legs axe arti- 

 culated far behind the centre of gravity of the body, 

 and thus they are unable to support it in a horizontal 

 position, or any thing approaching to it. Those who 

 think of no otier use or office in a foot than that of 

 walking upon the solid earth, would be apt to regard 

 the foot of a grebe as the most unformed and awkward 

 of all organs with which any animal could be furnished ; 

 but when we come to consider the use which the 

 grebes make of this apparently awkward foot in the 

 most important operations which they have to per- 

 form, we at once see that there is not in the whole 

 range of the animal kingdom, wide and varied as it 

 is, a finer instrument than the foot of the grebe. No 

 human knowledge of the principles of mechanics 

 could contrive such an instrument, and no human 

 dexterity could form it, even though in possession of 

 the plan. Oars and paddles, and other implements 

 for the moving of boats and other craft through the 

 waters, have been made of various forms and used 

 with different degrees of erl'ect in proportion to the 

 power necessary for putting them in motion. Among 

 them all, however, there is nothing which can be at 

 all compared with the foot of the grebe, even if we 

 leave its self-motion out of the question, and look 

 upon it merely as a mechanical instrument. When 

 the bird is under water (and it is rarely a surface 

 swimmer) the foot is both oar and rudder. In giving 

 the stroke which impels the body forward, the foot 

 acts with the maximum of power in the direction 

 which gives the power the maximum of effect. In 



