OF THE GAMASID^. 10.= 



EXPLANATION OF PLATE IX. 



Nymph of Gamasirs Iwrticola, Megnin (CoJeopfraforum, Lat.), 



showing division of dorsal plate, x about 17 diam. I. p., 



labial palpus (or first leg) ; iii.p. , maxillary palpus. 



Mandibles and Maxillye of ditto seen from beneath, x about 



90 diam. m., mandible; max., maxilla; mas:./?, , maxillary 



palpus. 



Last joint of labial palpus of ditto, with claw and caruncle, 



X about 175 diam. 



Last joint of labial palpus of Uropoda (found on Forcellio 



scnher), with small caruncle and no claw, x about 175 diam. 



Last joint of labial palpus of nymph of a Gamasus, with 



entire dorsal shield, having neither claw nor caruncle, x 



about 175 diam. 

 ,, G. — End of hind leg of ditto, showing caruncle and large double 



claw, X about 175 diam. 

 ,, 7.— Nymph of Uropoda vegetans (De Geer), attached to dorsal 



plate of a Gamasus, x about 90 diam. 

 ,, 8. — First leg of Uropoda (from Porcellio scaber), showing how the 



legs are doubled up when the creature is at rest, x about 170 



diam. 



Sense of Direction in Insects. — Dr. H. C. McCook has 

 observed a very accurate sense of direction displayed by the 

 '• horse-ant " (Formica rufa) of Great Britain, in laying out roads 

 from the ant hills, to points in the surrounding woods. These 

 roads or trails had in places a width of from two to four inches, 

 and were distinctly marked upon the surface of the ground, which 

 was stained a dark-brown or black, probably by the formic acid 

 exuded from the insects, and the leaves and grass over which they 

 ran was pressed down and smoothed by the constant passing of 

 innumerable legs. From one large mound, three roads ran 

 beneath the tall undergrowth, with remarkable directness to different 

 oak-trees in which numerous aphides afforded a food-supply. 



Road No. I was about sixty-five feet in length, and ran in an 

 almost perfectly straight line. No. 2 was about seventy feet long, 

 and varied less than three inches from a direct line measuring 

 from the tree to a point within two feet of the terminal tree. 

 There the trail made a detour of about six inches. No. 3 was a 

 little over one hundred feet in length. A short distance from the 

 nest, it touched an old stump which deflected the path at a slight 

 angle, and further on it crossed a foot-path where the trail of the 

 ants was much interfered with by passing human feet. In spite of 

 the difficulties of the track, when the entire trail was staked off, 

 its terminus was found to deviate less than three feet from a 

 straight line drawn from the point of departure. 



Journal of Micro.scopy and Natural Sciencr. 

 New Series. Vol. II. 1889. 



