Fróðskaparrit - 01.01.1996, Side 113

BLOOD-SUCKING MITE DERMNYSSUS HIRUNDINIS FOUND IN A NEST OF SWALLOW
117
duce many eggs - hundreds up to thousands
of eggs depending on the different species.
The very short life cycle of the mites, less
than 10 days, makes it possible to establish
a huge population within a few weeks. The
presence of the huge amount of parasites in
the nest will certainly have negative effects
on the development of the nestlings. A
closely related mite, the tropical fowl mite
Ornithonyssus bursa, which also has been
found in the nest of swallows in Denmark
may even cause the death of the nestlings
(Gjelstrup and Møller, 1988).
Dermanyssus hirundinis is very similar
in morphology to D. gallinae, with broadly
ending dorsal plate. The dorsal plate of D.
hurindinis bears 11 pairs of setae compared
to the dorsal plate of D. gallinae that bears
15 pairs of setae. In fine details many other
characteristics distinguish the species from
each other.
The mites of the family Dermanyssidae
develop through the following stages: egg,
larva, protonymph, deutonymh and the
adult stage. Nymphs and adults all seem to
be blood-sucking stages. The adult popula-
tion in the nest from Tórshavn made out
half of the mites, and the rest were at the
deutonymph stage. The adult mites have at
least sucked blood three times (an egg lay-
ing female may however suck blood seve-
ral times), and the deutonymphs two times
during their development. This means that
there have been sucked blood more than
15.000 times from the swallows that inha-
bited this nest during the summer. When
sucking blood, the mites engorge them-
selves quickly and the intake of large quan-
tities of blood or lymph during feeding re-
sults in considerable enlargement of the
body. Then they leave the host to find a
suitable place to hide.
The Faroe Islands lies at the extreme bor-
der of the distribution of the swallow.
Therefore the survival rate for specimens of
D. hirundinis left in nests in the Faroes may
be very questionable.
Few of the nests in the Faroes do get oc-
cupied the following year. The reason may
be that the swallows do not retum to the
Faroes, or that the nest is too fragile for re-
occupation. Another possibility is, that the
swallows are aware of the infection rate of
the nests.
In 1992 another nest of swallow from