300 DR, JOHNSTON ON THE ACARIDES OF BERWICKSHIRE. 



beautifully pectinated on the outer edge, and one of them fur- 

 nished -with two or three long moveable setce. The mandibles 

 are large and powerful. They are situated above, and internal 

 to the palpi ; and each mandible consists of a two-jointed cy- 

 lindrical shaft, capable of being pushed far beyond the palpi, 

 or withdrawn underneath them, and terminated with a pair 

 of elongate powerful brown-tinted chelaj, denticulated on 

 their inner or cutting edges. 



As I cannot reconcile this description to that of Dug^s, 

 I am doubtful of its accuracy. Dug(>s says that the palpi 

 are of moderate size, armed with a mobile bristle, and are 

 used in cleansing the mandibles. The lip, he continues, is 

 broad, embraces the mandibular arms when they are pushed 

 out, and it is terminated by a mesial point and two lateral 

 fangs. The mandibular arms have a short simple slightly 

 toothed pincer, with a moveable nipper (mordant) placed 

 above ; they are formed essentially of two articulations fleshy 

 in part, and which can be retracted within each other like 

 the tubes of an opera-glass. The pincer is much compressed 

 and sufficiently sharp to pierce like a lance when its two nip- 

 pers are closed. The mouth is covered above with a sort of 

 triangular labrum, similar to the prolongation observable in 

 the Erythraeus and other Acarides.— So far Dug^s. 



The Gamasus coleoptratorum is an active insect. It is 

 found abundantly in the partially dried dung of horses and 

 kine, and in heaps of stable and curtain manure, running 

 about restlessly in search of what appears to be its more ap- 

 propriate habitat, for the mite is truly the parasite of the 

 scarabs or dung-loving beetles, especially of the shard-born 

 beetle of Shakspere, — the droning beetle of Gray, — of the 

 Necrophagi and Histeres. It loves also to infest our humble 

 bees.* When an insect so beridden is taken up, the mites 



• "You have doubtless often observed the common dung-beetles {Oeo- 

 tmpes Latr.) covered on the underside of their body with small mites {Ga- 

 mamis coleoptratoi-um Latr.) which -look as if they were engaged in suctioa 

 — they are often so numerous that no part is uncovered ; they also attack other 

 beetles, and are sometimes found on humble-bees. They are easily disturbed, 

 run with great swiftness, and may often be seen in hotbeds and fermenting 

 dung prowling in search of the stercorarious beetles." Kirby and Spence, 

 Introd. Entom. iv. p. 227. 



