290 
C. OLDHAM-HERTS MOLLTJSCA. 
P. crista (Linn.).—Pond, Elstree ( Bullen ). 
Aplecta hypnorum (Linn.).—Colne Meadows, near Watford. 
Bithynialeachii (Shepp.).—Park Street. 
Valvata cristata Mull.—Abundant in ditches in the Colne 
Valley at Park Street. 
Pomatias elegans (Miill.).—Not uncommon in many places in 
West Hertfordshire, e.g. Tring; Berkhamsted; King’s Langley; 
Munden; and Chandlers Cross, near Watford; Wheathampstead. 
Neritina fluviatilis (Linn.).—Canal, Tring. 
Sphaerium lacustre (Miill.).—North Mimms. 
Pisidium pulchellum Jen.—River Ver, Sopwell, St. Albans. 
P. obtusale Pfeiffer.—Park Street; Colney Heath. 
P. casertanum (Poli).—Watford. 
XXIX. 
NYCTERIBIA PE DIG ULARIA LATEEILLE {= N. LA TREILLEI 
LEACH) IN HERTFORDSHIRE. 
By Charles Oldham, P.Z.S. 
Read at St. Albans , 14th March , 1911. 
As examples of the curious aberrant dipterous flies, Nycteribia, 
all the species of which are parasitic on bats, rarely come into 
the hands of collectors, it may be well to record the occurrence in 
Hertfordshire of N. pedicularia , one of the two British species. 
On 4th February, 1910, I obtained four specimens from 
a Daubenton’s bat ( Myotis daubentoni) that was hibernating in 
a chalk cavern near Abbot’s Langley. Parasitism has induced 
great changes of structure as well as of habit in these insects. 
A Nycteribia bears no superficial resemblance to a “fly”; indeed, 
in the course of its evolution the compound eyes and the wings 
have disappeared altogether, although the balancers, which 
characterize the order Diptera, remain. Specialized hooks have 
been developed to enable it to cling to its host, and it makes its 
way through the fur with such ease and rapidity as to suggest 
a creature swimming rather than one forcing its way on foot 
through so dense a medium as a bat’s coat. 
Trans. Hertfordshire Nat. Hist. Soc., Vol. XIV , Part fr, July, 1912. 
