A SYNOPSIS OF AUSTRALIAN ACARIXA — RAINBOW. 159 



LePTUS (IdVVOi). 



Host. — Day-flying Moth — Procris viridijndverulenta, Guer. 

 (the writer). 



Hah. — Sydney 



Ohs. — Mr. Goldfinch has also observed a Leptus on a moth, 

 Sericea spectans, Gn. 



Snper-family HY DRACHNOIDEA. 



Famihj HYDRACHNID^. 



In this family only one species, Hydrachna oduntoyiiathus, 

 Canest., has been I'ecorded from Australia, and two more are now 

 added — Eylais maccidlochi and Atax cumberlaudensis. The 

 family is extensive and widely distributed, and the species occur 

 not only in fresh and brackish water, but also in the sea. All 

 are free-swimming as a rule in the adult stage, but in the larval 

 state they are parasitic. In the Hydrachnida?, the integument is 

 entire, there being no division between the cephalic and thoracic 

 regions, and the body is more or less convex, spherical or bi'oadly 

 ovate. In some genera, as in Ai'renurus, Duges, the male has an 

 elongated abdomen tipped with a median projection called the 

 petiolus. In the genus Eylais there are four simple eyes situate 

 close together on a plate near the median line, whilst in Afa.v, 

 Fabr., there are only two, and these are widely separated. The 

 integument is soft, and the animals are either scarlet or bluish- 

 green ; according to Banks, some American species are prettily 

 marked with yellow and black, and vary consideral)ly in macula- 

 tion. The mouth-parts are often hidden under the anterior 

 margin of the cephalothorax, and the maxillary palpi, consisting 

 of four or five joints, varies so much, that it is of great value to 

 the systematist in classification. The legs are usually of equal 

 length, although it is not uncommon .to find the first pair some- 

 what the longest ; normally they are seven-jointed, and clothed 

 with long hairs which aid them in swimming ; in this respect 

 the third and fourth pairs are much more densely hairy than the 

 others. 



Genus Eylais, Lafr. 



r= Eulais, Piersig and Lohmann. 



Eylais maccullochi, sp. nor. 



(Fig. 36). 



Scarlet, elliptical, strongly arched, integument smooth ; moutli- 

 parts hidden under anterior margin of cephalothorax. Body. — 



