200 
Bucentes (Siphona) geniculata 
Great Britain. It is recorded from Devon, Hereford, Hants, Kent, Radnor, 
Middlesex, Hampshire and Inverness-shire. We have found it in Northumber¬ 
land and Aberdeenshire. 
The adults of this fly are recorded over the period from May till Sep¬ 
tember. Schiner (1862) writes regarding the genus: “ The flies live in dry places 
especially heaths. They are also found on Umbelliferae and on waste ground 
are often to be seen in large crowds on Daucus carota. " He also states that 
B. geniculata visits Erica vulgaris. Walker (1853) reports these flies as “very 
common.” 
The following list of flowers known to be visited by B. geniculata is com¬ 
piled from Knuth’s Handbook of Flower Pollination (1909). 
Viola lutea. 
Stellaria holostea. 
Medicago lupulina. 
Potentilla sylvestris. 
Potentilla sterilis. 
Daucus carota. 
Hedera helix. 
Asperula cynanchica. 
Asperula odorata. 
Valerianella olitoria. 
Succisa pratensis. 
Eupatoria cinnabinum. 
Pulicaria dysenterica. 
Myosotis sylvatica. 
Mentha aquatica. 
Origanum vulgare. 
Hottonia palustris. 
METHODS OF INVESTIGATION. 
The Tipula larvae, after being washed free of soil, were examined individu¬ 
ally and with a little practice the parasitic maggot could be readily recognised 
beneath the skin of the host larva as an elongated yellowish patch of definite 
shape. 
The proportions found to be infected varied a good deal in different 
localities and in different years. In one area, viz. Echt, Aberdeenshire, the 
numbers reached a significantly high figure. Over a period of one month, 
during which larvae were examined, a progressive decrease in the percentage 
of infected individuals was noted. This was found to be due to the fact that 
as the season advanced, the infected larvae were dying off, and pupae of 
Bucentes were becoming increasingly more numerous in the soil. It must 
therefore be borne in mind that for the first generation, unless examinations 
are made not later than about February, any estimate of the degree of infection 
must be below that actually existing. The following data illustrate this: 
