Photo 1. The geranium bronze butterfly on the flowerhead of an ivy-leaf
geranium (Pelargonium peltatum) in the Town of Krk, 27 July 2014. (Photo
by Stjepan Janeković)

THE GERANIUM BRONZE BUTTERFLY (Cacyreus marshalli) ON THE ISLANDS AND COAST OF THE COUNTY OF PRIMORJE AND GORSKI KOTAR

Recently on our Web
pages we posted a brief report on the large-scale appearance
of the geranium bronze butterfly in the Town of Rijeka.

After the report was posted, Mr Stjepan Janeković, an
associate of PI “Priroda”, contacted us with information about the appearance
of the butterfly on Krk Island (Town of Krk). He has published an interesting
and informative article about the butterfly in the journal Krčki Val.
With his kind permission, and courtesy of the Editor in Chief of Krčki
Val, we bring you a
copy of the article.

We have become increasingly aware of the geranium bronze
butterfly in the County of Primorje and Gorski Kotar. Mostly during the
month of September we have spotted adult butterflies, and damage caused
by caterpillars, in the region of Klana (on Pelargonium zonale plants),
at Grobničko Polje – Dražice and Podkilavac (on ivy-leaf geraniums – P.
peltatum), in Crikvenica (on P. zonale and P. peltatum), in Opatija (on
P. zonale and P. peltatum), in the Town of Cres (on P. zonale and possibly
on an unidentified ornamental plant, probably belonging to the family
Geraniaceae or Malvaceae – this requires further investigation), in Njivice,
Kijac and Punat on Krk Island (on Pelargonium sp. div.; at Kijac only
an adult butterfly was sighted), at Batomalj near Baška (on P. zonale),
and on Košljun Islet (on P. zonale and P. peltatum).

It is important to note that possibly the first case
in Croatia (Cf. Kučinić et al., 2013) of geranium bronze caterpillars
feeding on the leaves of a species of ornamental cranesbill (Geranium
sp.) was recorded in the Japanese garden of the Vežica Elementary School
in Rijeka.

Our small “jigsaw puzzle” of observations could prove
helpful because it is important to establish the appearance and spatial
distribution of this invasive butterfly species within the complex mosaic
of its spreading, which it seems is partially dependent on current climate
changes and fluctuations.

Keywords: geranium bronze butterfly, geranium (Pelargonium),
invasive species, cranesbill (Geranium), gossamer-winged butterflies (Lycaenidae)

Marko Randić

Photo 2. The caterpillar of the geranium bronze butterfly bores into the
stem of a geranium. This is followed by a secondary fungal infection which
can cause considerable damage to geraniums cultivated as ornamental, balcony
plants. Rijeka, Vežica, September 2014. (Photo by Marko Randić)

Photo 3. A hole chewed by a geranium bronze caterpillar in a leaf of an
ornamental cranesbill (Geranium sp.), Rijeka, Vežica, Japanese garden,
September 2014. (Photo by M. Randić)