APiPENDIX. 251 



high magnifying power display the same structure as 

 the larger species, and this may also be said of BecJcia 

 argentea, which, although somewhat thinner, is very 

 similar in structure to B. albinos. 



I had thought of adding an illustration of the appear- 

 ances produced on the same scale by variations in the 

 direction and character of the illumination ; also one 

 of the effect produced by placing two ribbed membranes 

 over one another at an angle ; also one showing the 

 result of running moisture along the corrugations in the 

 under surface of the scale ; but illustrations of these 

 experiments hardly come within the compass of a work 

 such as the present, the object of which is to enable 

 observers to identify the several species. 



Plate LXVII. 



Tomocerus longicornis. 



Scale. — Dark continuous compound stride, lines or 

 corrugations, parallel to the pedicle; clearly defined 

 cross strige between, and at right angles to the longi- 

 tudinal ones ; a tendency to broad strige radiating from 

 the pedicle ; under surface of scale deeply corrugated 

 from pedicle to apex ; upper surface of scale free from 

 all corrugations, smooth ; cross striee due to structure 

 between the superposed membranes. Under a power 

 of 4000 diameters an appearance of beads between the 

 longitudinal strise is readily obtained ; this is not the 

 structure, but due to illumination. 



Plate LXVIII. 



Tomocerus ^lumheus. 



Scale. — Dark continuous compound strise, lines 

 or corrugations, parallel to the pedicle ; indications of 

 cross strige between and at right angles to the longi- 

 tudinal ribs ; broad strise radiating from the pedicle ; 



