288 
C. OLDHAM-LAND AND FRESH-WATER 
fSphserium corneum (Linn.), 
t Pisidium amnicum (Miill.). 
t P. subtruncatum Malm = fontinale Jeffr. 
# P. casertanum (Poli). 
# P. gassiesianum Dupuy. 
Among some Mollnsca collected in February on a hedge-bank 
at Tring, I found dead shells of Vitrea rogersi , V. nitidula , 
V. cellaria, and Pyramidula rotundata, each of which had in its 
last whorl a small reddish pupa. From these several specimens 
of a dipteron, Sciomyza dubia, hatched out in April. Almost 
nothing is known of the life-history of this fly, and I cannot say 
whether the larva is parasitic on the living mollusc, kills and 
subsequently devours it, eats the body of the snail which has 
died from some independent cause, or merely chooses the empty 
shell as a convenient place in which to pupate. 
Mr. Gr. E. Bullen has favoured me with some interesting notes 
on the homing habits of the slug Limax maximus. In the latter 
part of October he noticed a full-grown example at rest on an 
upright beam in an outhouse in his garden at St. Albans. Its 
slime-track suggested that it had entered the outhouse through 
a small hole in the wooden wall. The slug was removed to 
a rockery about 10 feet away from the shed, but by the next 
day it had returned to its former resting-place on the beam, 
some 19 inches from the ground. It was again removed and 
placed on the rockery, only to return as on the first occasion. 
Mr. Bullen then placed the slug at a greater distance—some 
20 feet—from the shed, and it again returned to its chosen 
resting-place. A fourth ejection from the shed had a like 
result. The slug was then carried to a hedge at the end of the 
garden, about 80 yards from the outhouse, but on the following 
morning it was back again in the accustomed spot, and was not 
thereafter molested. 
I am only able to record one species— Limax cinereo-niger — 
that is new to the Hertfordshire fauna, but such desultory 
collecting as I have been able to do has resulted in the addition 
of new localities for some of the less common species, and I am 
indebted to Mr. Bullen for others. 
Limax cinereo-niger Wolf.—Two juvenile examples beneath 
the bark of a dead beech, Aldbury Owers, near Tring, 
November 13tli. 
L. flavus Linn.—St. Albans ( Bullen ) ; Hemel Hempstead. 
L. tenellus Miill., var. cerea Held.—Prse Wood, St. Albans. 
I found young specimens on trunks of beeches at Ashridge so 
early as July 9th. 
Agriolimax Idevis (Miill.), the typical form with the var. 
maculata Cock.—Among rushes in low-lying meadows at Park 
Street. 
Milax sowerbyi (Fer.).—St. Albans ( Bullen ) ; Hemel Hemp¬ 
stead. Yar. nigrescens Cock.—Watford. 
