Photo © M.Hoskovec
|
Necydalis ulmi Chevrolat, 1838 is a remarkable insect species of the West-Palaearctic region.
The species is distributed throughout Central and South Europe, and the Caucasus, reaching the
Transcaucasian region, and requires old well preserved broad-leaved forests
(cf. Figure 1) growing in altitudes ranging from 0 to 800
metres above sea level. A paper dealing with larval nutrition and female oviposition preferences of
some Necydalis species has appeared recently (Rejzek and
Vlasák, 2000[1999]). In this paper the biology of Necydalis ulmi is summarised in
the following way:
"Necydalis ulmi develops primarily in Fagus sylvatica, Quercus cerris, and
Aesculus hippocastanum. As alternative host plants other Quercus spp., Ulmus,
Carpinus, Celtis, Tilia, and also Fraxinus, Populus, Salix,
and Juglans should be named. The larvae of Necydalis ulmi develop in a substrate present in
the inside of hollows of living trees (cf. Figure 2). These hollows are
created by two species of polyphores: Inonotus obliquus (cf. Figure 3a)
and Inonotus cuticularis (cf. Figure 3b). The inside of a typical
hollow is in parts covered with a thin and dry black layer (cf. Figure 4).
Next there is a thick layer of a quite moist, red-brown to yellow decayed wood, followed by the firm heartwood,
and finally the living tissue (sapwood). The red-brown to yellow wood that comprises the larval substrate has
a spongy-fibrous structure typical for wood decayed by various white rot (ligninolytic) fungi. Their mycelium
regularly create a yellow to red-brown circle surrounding the larval galleries
(cf. Figure 5). This mycelar circle is well recognisable on the substrate
background and serves as a clear hallmark of the species presence. The convenient substrate is not only
present inside the hollows, but it is also regularly present inside a substantial part of the living trunk,
especially in the part above the hollow entrance. The substrate completely surrounded by living tissue is of
a different colour to the insides of the hollows. It is usually light yellow and therefore the mycelar
circles surrounding the larval galleries are more clearly visible because the circles are of a contrasting
red-brown colour. Sometimes, the entrance into the hollow is small and hardly visible, and although the tree
seems to be perfectly sound, a substantial part of the heartwood is decayed, infested by fungi, and by
larvae (cf. Figure 6) of Necydalis ulmi."
|
|
| Body length: | 18 - 35 mm |
| Life cycle: | 3 - 4 years |
| Adults in: | June - August |
| Distribution: | Central and South Europe, Caucasus, Transcaucasia |
The mounted beetle and living beetle in the upper pictures were collected in a hollow trunk of an old living beech tree
(Fagus sylvatica) in Bezděz Mt. (North Bohemia, Czech Republic). The living beetle in the lower pictures was reared from a larva
collected in a hollow trunk of a living beech tree (Fagus sylvatica) in Křivoklát (Rejzek and Rebl, 1999), Central Bohemia
(Czech Republic).
Collected by M.Rejzek and M.Hoskovec.
|
