1913.] 269 



Moccas Pool on July 22inl, 1912. At the time tliey were tliouglit to 

 be Verrall's Isetus, on account of the dark colour of the thoracic 

 bristles and the black hypopygium. But when Mr. Collin visited me 

 early in last Aut^'ust, and we swept the true leetus at the opposite and 

 shallower end of the pool, I was al)le to compare the two forms, and 

 to see how thoroughly distinct they were. There is also, I learn, 

 a damaged male in Verrall's collection, taken at Ormesby Broad 

 (Norfolk), as far back as June 22nd, 1881, and which he had separated 

 out as a distinct species, but had refi'ained from introducing, when 

 dealing with Thrypticus in his last " Hundred New Species," from the 

 scantiness of the material. 



S ? . Bright green. Dorso-central and acrostichal bristles dusky (darker 

 in some specimens than in others), the other thoracic bristles yellow. Face 

 blue ; arista very long (longer than in any Thrypticus I know), slender and 

 pointed. Veins 3 and 4 parallel and not divergent at the margin ; the part 

 of vein .5 on the inner side of the X-vein distinctly longer than that on the 

 outer side (in Isetus the proportions are reversed). Legs black, the tibiae browner 

 and the knees yellow. The end piece or lamellse of the hypopygium quite 

 black, very large and distinctly longer than the joint of the stalk above it ; 

 ovipositor testaceous, paler at the base, very long and, inclusive of the bulb at 

 base, as long as the last two abdominal segments. In Ixtus the end piece only 

 of the hypopygium is dark brown, and considerably shorter than the joint 

 above it ; whilst the ovipositor is short and black, and not longer with its bulb 

 than the last alidominal segment. The proportion between the joints of the 

 hypopygial stalk is also different in the two species. Measured along the 

 upper border they are of about equal length in Isettis, but in nigricauda the 

 basal joint is longer than the end one. 



Argyra grata. This interesting species was met with again this 

 year in its original locality at Mordiford. A male and two females 

 were obtained on July 20th by sweeping the rocky l)ed of the little 

 Penteloe stream, where it runs hidden away under thick overhanging 

 bushes. It is the smallest of our British species, and is without a 

 trace on thorax or abdomen of the beautiful silvery hue, the usual 

 characteristic of the genus. Its chief distinction lies in the colouring 

 of the abdomen, the sides of which on segments 2, 3, and 4 are in 

 both sexes semi-transparent and yellow, segment 2 being almost 

 wholly yellow, and 3 and 4 in gradually diminishing degrees, 



Achalrus cinereus. The habitat for this little-known species is a 

 bit of rough ground outside a small wet wood some two miles from 

 where I live. Here I came across it for the first time on August 15th, 

 1912, when sweeping the dense patches, 3 or 4 ft. high, of the big 

 Carex, C. riparia. From this date up to my last visit on October 19th, 



