DESCRIPTIONS OF GENERA AND SPECIES. 241 



and is one of the great destroyers of dried animal and 

 vegetable stores ; but it is not by any means confined 

 to houses. It is frequently confused with G. spinipes, 

 and is at first very difficult to distinguish from that 

 species ; when the observer is accustomed to the two, 

 however, he can pick them out readily; even the 

 novice, if he can use a microscope properly, may easily 

 do so by the following characters : firstly, the tarsi of 

 the present species are smooth and have on them only 

 a very few (four to six) moderately long setif orm hairs, 

 which are easily seen ; those of G. spinipes are densely 

 clothed with very short fine hairs which are difficult to 

 see and almost invisible in glycerine, or indeed in 

 almost any liquid or in balsam ; they are best seen dry 

 with an amplification of 150 to 200 diameters ; but 

 none of these hairs are much longer than their fellows. 

 Secondly, the tarsi of G. domesticus are much longer 

 than those of G. spinipes ; in the former species the 

 tarsi are as long as all the other joints of the leg put 

 together. Thirdly, the third' joint of the third leg of 

 G. spinipes bears on the outside a peculiar hair or scale 

 (PL VII, figs. 5, 6), shaped like a husk of corn, and 

 placed with the concavity inward ; its outer surface is 

 thickly clothed with very fine hairs like those on the 

 tarsi ; this scale is absent from G. domesticus. Fourthly, 

 the bursa copulatrix of the female G. domesticus is 

 twice as long as that of G. spinipes. Fifthly, G. spinipes 

 is sharply constricted between the second and third 

 pairs of legs, and is much narrower behind the con- 

 striction than before it; whereas G. domesticus can 

 hardly be said to be constricted at all, although slightly 

 curved inward, and its abdomen is nearly or quite as 

 wide posteriorly as anteriorly ; this difference of form 

 can only be seen in living specimens. 



Colour pearly white or very pale grey ; generally 

 bluish grey on the side next the light, but yellowish 

 white on the side opposite the light ; the creature 

 being somewhat translucent. 



Texture even, but not smooth or polished ; the 

 16 



