NORSK ENTOMOLOGISK TIDSSKRIFT - Norsk entomologisk forening

124 Albert Lilleharnmer
damanlegg). Det er derfor trolig at en ~esentlig~del av den plagsomme
knotten i Lande var rekruttert fra bekk B, selv om man
ikke kan se bort fra at insektene ved gunstige vindretninger kan
bli ferrt fra Stenbekken ti1 bebyggelsen p$ Lande. En naturlig
minsking i vannstanden i bekkene finner sted i slutten av juni
og begynnelsen av juli. Dette kan vzre en medvirkende grsak
ti1 de store svermer av knott, idet en slik inntaking som nevnt
kan utlerse masseklekking. Ved 5 velge $ fremskynde innterrkingen
ti1 tiden f0r knottlarvene forpupper seg, kan en i disse smgbekkene,
bekjempe knotten effektivt uten 5 bruke kjemiske midler.
Det synes sgledes $ fremg% av resultatene fra denne underserkelse
at en kan utferre biologisk bekjempelse av knotten der forholdene
ligger ti1 rette for det.
Summary
The black fly has been an intolerable plague for many years
both for man and cattle in the locality of Lande, near Sarpsborg,
in East Norway.
Upon request, Mr. Per Knudsen and the author agreed to
attempt to localize the biotopes of the larvae.
It was found that in at least some creeks (figs. 3A, B and C) larvae
were present in very large numbers (tab. 1). The larvae were
kindly determined by Dr. Phil. G. Carlsson, Halsingborg, Sweden,
and were found to belong to Simulium argyreatum Meigen.
As is well-known, the larvae are filter feeders and therefore
depend upon running water for catching food. We accordingly
recommended that the creek outlets should be closed-off for a
time. This could easily be done as the streams carry little water
during the summer. The closing-off had to be done before pupation
proper as a fall in the waterlevel at pupation time could
lead to mass-hatching.
The time for the investigation of the larvae population was
fixed for the first part of June because the larvae are then at a
later instar and easy to see. Control was carried out immediately
after the investigation and before pupation. The closing-off of
the outlets of Creeks A and B was carried out in 1963 and 1964.
Just in these two particular years attacks worth mentioning by
black fly have not been recorded. In the surrounding localities,
however, attacks have continued as hitherto.
References
CARLSSON, G. 1962 : Studies on Scandinavian Black Flies (fam. Simuliidae
Latr.). - Opusc, ent. Supplem. XXI, 279 p.
ENGELHARDT, W. 1959: Was lebt in Tiimpel, Bach und Weiher. - Stuttaart.
258 D.
ILLIES,~ J. ' 1956: Seeausfluss - BiozBnosen Lapliindischer Waldbache.
- Ent. Tidskr. 77, H. 2-4: 138-153.
MELLANBY, H. 1956: ~nimal Life in Fresh Water. - London, 296 p.