DR. JOHNSTON ON THE ACARIDE8 OF BERWICKSHIRE. 281 



applicable and, in one or two particulars, discordant, for Fa- 

 bricius must be somehow in error. I add the description to 

 complete the history of our mite : — " Corpus ovatum, gla- 

 brum. Antennae quadriarticulataj, filiformes. Caput et tho- 

 rax sanguinea. Abdomen valde obtusum, magis obscurum 

 utrinque punctis aliquot impressuuL" — Entom. Syst iv. 433- 

 44. 



5. Hydrachna crdknta, MvM. 



Hydrachna cruenta, Mull. Zool. Dan. prod. 191, no. 2273. 

 MuU, Hydrach. 63, tab. 9, fig. 1. 



Hab. Ponds, frequent. 



Desc. Insect of a uniform scarlet colour : Body rounded, 

 swollen, somewhat flattened on the dorsal and ventral sur- 

 faces, rather narrowest in front, smooth : Eyes 4, a pair on 

 the outer and anterior angles of the body ; one eye behind 

 the other ; sometimes only two are distinguishable, and even 

 these with difficulty : Palpi 4-jointed, the terminal joint 

 conical, pointed and slightly curved at its claw-like extre- 

 mity : Legs 8, approximate at their origins, alike, slender, 

 the posterior pair longest, and longer than the body, hirsute, 

 and the tibial joints of the posterior pairs are besides fur- 

 nished with long hairs on the outer edge ; they are 6-jointed, 

 the two basilar joints short, 3d longer, 4th, 5th and 6th elon- 

 gate, the latter slender, cylindric, terminated with two small 

 claws which can be drawn backwards and concealed in a 

 sinus at the end of the joint. 



This pretty insect is not uncommon in our district, and 

 its colour renders it conspicuous. The body and legs are 

 alike scarlet and unspotted, yet when attentively viewed some 

 dusky indistinct bands may be perceived on the back, — too 

 distinctly represented, however, in Muller's figure. The back 

 is irregularly uneven or depressed. The skin seems to be 

 minutely papillose under a high magnifier. In one specimen 

 I perceived with difficulty two eyes only ; in another four 

 were plainly evident. Muller says that there are only 2 in 

 his H. cruenta. The palpi are proportionably small when 

 compared with Atax histrionicus, and only occasionally visi- 

 ble, being hidden under the bulging front. All the tarsi have 

 claws. 



