DIGITALNA ARHIVA ŠUMARSKOG LISTA
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ŠUMARSKI LIST 9-10/2017 str. 48     <-- 48 -->        PDF

Host plants – Biljke domaćini
In its natural habitat of North America C. amoena develops in broad spectrum of suitable firm substrates as fallen unripe and ripe frassy apples (Malus domestica Borkh) and native crabapples (Malus coronaria L.), oak acorns (Quercus spp. L.) and black walnut husks (Juglans nigra L.) (Band, 1991; Band et al., 2005; Jong & Van Zuijlen, 2003). Several studies in forests and orchards in Central and Southern Europe have confirmed its presence in chestnuts (Castanea sativa Miller), pedunculate oaks (Quercus robur L.) as well as in fleshy fruits such as apples (Malus domestica Borkh), wild sweet cherries (Prunus avium L.) and plums (Prunus domestica L.) (Band et al., 2006).
The ability of C. amoena larvae to live in various parasitized or damaged fruits and nuts, feeding on decaying frass and other media supporting micro-organisms shows that this species can be considered a food generalist (Band & Band, 1984 cit. Máca & Bächli, 1994).
Morphology and biology of species – Morfologija i biologija vrste
The body length of species ranges between 2 and 4 mm. C. amoena has strikingly bright red eyes, yellowish to brownish matt colored thorax and black brownish colored abdomen (Insekten Box, 2017). Morphological characteristics unique to this species are yellowish legs and wings with two distinct brown transverse bands and a dark spot along R1 (Bächli et al., 2004) (Figure 1).
The biology of C. amoena was studied in detail in North America. It is a multivoltine species which can produce a new generation within a month during the breeding season (Band, 1988). The most Chymomyza species breed under the bark of various trees and the adults are usually attracted to the peeled areas of trees and to cut logs. C. amoena is the exception while it breeds in parasitized fruits and nuts damaged from primary pest attack (Bächli et al., 2004, Band et. al, 2005). In eastern United States, the species overwinters as the third instar larva in a variety of substrates such as black walnut husk, native crabapples and domestic (imported) apples and breeds from spring through autumn. In spring, females prefer to oviposit in soften overwintered native crabapples and later in fallen parasitized plums. In summer oviposition continues in early fallen parasitized unripe apples as well as in ripening parasitized fallen and unfallen apples. Parasitized apples and pears may continue to be used for oviposition in autumn but females also switch to nuts, especially parasitized black walnut husk and other suitable substrates which will serve as overwintering sites for the developing larvae. In early fallen and ripening apples, females oviposit in scars, codling moth tunnels or frass which also serves as food for females. In nuts, it prefers parasitized rather than just damaged acorns and use native crabapples as the breeding substrate (Band, 1988; Band et al., 2005). Experimental studies in Europe have revealed that breeding in parasitized fruits and nuts had been maintained in European specimens of C. amoena. Further research established its presence in European apple orchards and chestnut forests and is considered to be the principal drosophilid breeding in parasitized fruits and nuts in both North America and Europe.
First record in Croatia – Prvi nalaz u Hrvatskoj
C. amoena was first recorded in Croatia on 6th October, 2016 on locality Zebanec Donji (Međimurje County) situated in northern part of Croatia, at N 46°28ʹ1.2ʹʹ, E 16°24ʹ0ʹʹ (Figure 2). Two male specimens of fly were caugth in integrated production vineyard situated relatively close to the border with Slovenia by feeding traps based on apple vinegar.
The grape cultivars traditionally grown in this region are Sauvignon blanc and Riesling. The climate of this region is of a moderate continental type, with warm summers and maximum precipitation in the spring and summer. The average temperature of the coldest and warmest months (January and August) is -2°C and 25°C, respectively. Average annual precipitation is 850 mm. The collecting site is surrounded by forest and extensive production orchard in which apples (Malus domestica Borkh), pears (Pyrus communis L.), sweet cherries (Prunus avium L.) and walnuts (Juglans regia L.) are grown.
Left and right hind wings were removed from two male individuals and slide mounted according to the standard procedures (Upton & Mantel, 2010) by using the fixing agent Euparal (Australian Entomological Supplies, Melbourne, Australia) (Figure 1). The keys and illustrations by Bächli et al. (2004) were used for the species identification. Slide mounted specimens are deposited in the Department for Agricultural Zoology, University of Zagreb, Faculty of Agriculture (Det. G. Seljak, leg. M. Šubić).