C. D. SOAR on hydrachnidj:. 321 



the hard-skinned Arrenurus, can never be imitated with the 

 palette. Bright as some of the colours may appear on the 

 table, they are tame when compared with the vivid colouring 

 exhibited by these mites when in their best state. 



Once this season, on June 22nd, the Hertford Heath Excur- 

 sion afforded a very good opportunity for observing that these 

 mites were not nearly so brilliantly coloured when they first 

 came out from the inert stage. A quantity of Arrenurus, both 

 male and female, of a pale yellow colour and with soft skins, 

 such as I had never met with before, were taken. 



At first I thought they were another species, but after 

 examining about a dozen or so they were found to be Arrenurus 

 caudatus, Imago stage, but not fully developed. The males 

 were nearly oval in shape, except that the tail portion projected 

 slightly, and in different specimens the tail projected more and 

 more, until the perfect form was reached. The colouring at 

 the same time got more marked and beautiful, going from the 

 yellow to the deep slate-blue. This I have endeavoured to 

 show in the drawing. The spur on the fourth pair of legs was 

 present from the first. The female was yellow and soft bodied, 

 but she also grew and hardened at the same time, and attained 

 her beautiful colouring when fully grown. The female seemed 

 to grow in the body portion only, that is to say, the genital 

 plates and the epimera remained the size they were in the 

 least developed specimen, but the other parts gradually swelled 

 up and hardened, and also assumed at the same time the beauti- 

 ful colour they are so well known to possess. {Arrenurus caudatus 

 is probably one of the most beautiful mites known.) There is 

 another important feature in this genus which also developed 

 itself as the growing process went on. In the early adult 

 stages the depressed line on the dorsal side, which is one of its 

 chie characteristics, was not seen ; but subsequently this 

 gradually came out distinctly. 



In conclusion, enough has been said to show how little I 

 know and how much more I have yet to learn about these 

 beautiful creatures, but I shall have much pleasure in answer- 

 ing, so far as lies in my power, any questions on the subject. 



Journ. Q. M. C, Series II., No. 40. 23 



