NOTULAE ENTOMOLOGICAE - Helda

124 NOTUr,AE ENTOMOI.OGICAK XUII, 1963
localities in Finland (Esbo: Småholmen, Kyrkslätt: Evitskog and Nykarleby:
Bonäs) previously studied by the author (HACKMAN 1963). In northernmost
Lapland the soil layers at 20—30 cm depth do not warm up much during the
short summer and even in sun-exposed places the night temperature rarely
rises above +5°- As, on the other hand, the surface layers in sunny places
may warm up considerably during the day, considerable diurnal fluctuations
are to be expected in the burrows. In shady places on northern slopes the bur-
row temperatures will remain low during the entire season.
During the period June—August in Bonäs and on Småholmen the temperature
in the Microtus burrows studied did hot fall below +8° and the
diurnal variations were usually rather small even on sunny days. As far as the
temperature is concerned the burrows in the extreme north, in Kevo, seem
not to be very favourable for insect life. The lemming burrows on shady northern
slopes can be considered as extreme biotopes.
3. The material
The sampling, which began on June 16, was done with the help of 12 funnel
traps and 9 Barber traps, both without bait, and 3 funnel traps baited with
cheese were used. Two of the baited traps were placed in burrows with the
funnel side outwards, one with the funnel inwards in the burrow and all three
in the vicinity of the station (one in a burrow of type 3, the other two, one
turned outwards, one turned inwards, in burrows of type 2). To avoid losses
in the funnel traps caused by spiders, those in the vicinity of the station were
examined at 2 day intervals; the Barber traps at Patoni va (burrows type 1)
were examined once a week. Specimens collected during a 7—8 day period
from one and the same burrow were combined into one sample. A survey of
the material is given in table 2.
The amount of material (320 specimens in the traps without bait) is rather
small and does not allow an analysis of differences in the composition of the
fauna of the three different types of burrows considered here. But it can be
noted that in spite of the low temperature prevailing in burrows of type 3
(lemming burrows, N. slope) the trapping results in these burrows were
not poorer than in the two other types (see tables 2 and 3).
The dipterous families which appear to be of importance are almost the
same as in burrows from more southern localities in Finland (Bonäs, Småholmen,
Evitskog). It must be noted, however, that the period of investigation
in Kevo did not cover the entire period of imaginai activity of the burrow
Diptera. From Table 3 it can be seen that the first capture period (15—22.VI)
gave the highest number of specimens. It is also obvious that continued trapping
after August 8 would have given noteworthy results.