4 6 



SCIENCE- G OS SIP. 



specimen, given to him by that gentleman. As the 

 name implies, the rostrum is longer than in any 

 other species of Thyas yet known, and is very con- 

 spicuous. The unpaired median eye is surrounded 

 by an elliptical chitinous ridge, extending in a line 

 anteriorly and posteriorly, thus distinguishing it 

 from other members of this genus. I may mention 

 that Professor Sig Thor, of Christiania, considers 

 this mite to be Neuman's Bradybates truncata, and 

 calls it Euthias longirostris. 



Length of female, 2'64 mm. ; breadth, 2-10 mm. 



Palpi. — 071 mm. 



4. Thyas vigilans Piersig 1896. 



This mite, only one specimen of which has been 

 as yet recorded in England, taken by Mr. Soar at 

 Sunningdale, May 7th, 1897. It is well and easily 

 differentiated from the other species of Thyas by 



creatures are very active, and soon escape, running 

 on glass or water or elsewhere with equal ease ; a 

 great contrast to their slowly crawling parents. I 



Fig. 6. Thyas vigilans. 

 Dorsal surface of female. 



Fig. 7. Thijus vigilans. 

 Genital plates. 



its very conspicuous median, unpaired eye, sur- 

 rounded as it is by the curiously almost racket- 

 shaped chitinous shield or frame, the posterior 

 portion of which is divided into two longitudinally. 

 This is well shown in Mr. Soar's figure 6. The 

 legs are very strong and thick, much like Thyas 

 petropMlus of Michael. 



Length of female, T30 mm. ; breadth, 0'88 mm. : 

 length of first leg, 0-64 mm. ; of fourth leg, 1-28 mm. 



5. Thyas thoracatus Piersig 1896. 



In this mite we have the median stigma, or un- 

 paired eye, placed in the middle of a rather large 

 thoracic shield of chitin, of an irregularly circular 

 form. Besides this character, there are embedded 

 in the skin of the back four rows of irregularly 

 shaped plates of chitin, and four smaller plates in 

 the skin of the under side of the. body. I foimd 

 this mite for the first time in April 1895, and have 

 taken it on several occasions since, including two 

 specimens on March 16th last. This species is, 

 however, not very easy to find, for I have been 

 to the same pond since without success. These 

 mites are very tenacious of life, and I have kept 

 them alive in a small glass vessel with a bit of 

 weed, a little mud, and some water for over a 

 year; they laid eggs, and in 1896 I had a con- 

 siderable batch of larvae. These very curious little 



thoracatus. Female. Dorsal view. 



do not know if they are parasitic, or what is their 

 natural host. Professor Sig Thor considers this 

 mite to belong to Koenike's genus Panisus. 



Fig. 9. Thyas thoracatus. Genital plates. 



Besides the specimen sent by me to Mr. Soar, 

 he has received one from Oak Hill, sent by Mr. 

 Scourfield. 



6. Thyas petropMlus Michael. 



In the ;1 Proceedings " of the Zoological Society 

 of London for March 5th, 1895, is printed a very 

 interesting and exhaustive account of a mite which 

 Michael calls T. petropMlus. The paper is illus- 

 trated with very fine plates, showing its external 

 and internal anatomy. Like the preceding mite, 

 it has a number of chitinous plates embedded in 

 the dorsal skin, but they are fewer in number than 

 in T. thoracatus, and are arranged in three rows. 

 Mr. Michael distinctly says that he could find no 

 trace of a fifth or median eye. Koenike and 

 Piersig both place this mite in Koenike's genus 

 Panisus. I have not found this mite, nor have I 

 seen it alive, but I have some mounted specimens 

 given to me by my friend Mr. Bostock, who was 

 the first to discover it when collecting with Mr. 

 Michael in the neighbourhood of Land's End, 

 Cornwall. 



Kirton-in-Lindsry, 

 April 1901. 



