Among beetles, most herbivores belong to the curculionid family. The distinctively elongated Lixus iridis Olivier (Curculionidae) (Fig. 11.7) feeds on the leaves and the stem of giant hogweed and other Apiaceae from the genera Angelica, Anthriscus, Petroselinum, Daucus and Carum (Hoffmann, 1954; Freude et al., 1983). For oviposition, the female first drills a hole into the stem with its mouthparts, then inserts its ovipositor and lays a few eggs into the hollow stem. After hatching, the larvae feed and develop inside the stem until autumn. After the pupation, the adult beetles hatch and hibernate there (Volovik, 1988). L. iridis is quite common at lower altitudes of the Caucasus Mountains, but is absent at high altitudes (Hattendorf, 2005). In central Europe, this species occurs only sporadically. With moderate infestation rates, the beetles did not cause significant damage to H. mantegazzianum (Hattendorf, 2005). However, two studies have reported damage caused by L. iridis to Levisticum officinale (Eichler, 1951) and to H. sosnowskyi (Volovik, 1988), but in neither case was the degree of damage specified.

Nastus fausti Reitter (Curculionidae) occurs in the mid mountainous forests in the alpine and subalpine zones from easternmost Europe and the Caucasus to North Ossetia and Transcaucasia. This species does not occur in western Europe. The larva feeds externally on the roots of several plant families. Since the beetle damages the roots, its impact on the plant is difficult to estimate. According to Arzanov and Davidyan (1996), little is known about

Fig. 11.7. Lixus iridis is 16-22 mm long and one of the largest herbivorous insects on giant hogweed. The adult feeds on the leaves and its larva develops inside the hollow stem until it pupates. Drawing: S.O. Hansen.

host plant preferences, but the species from this genus are said to be non-specific. Adult beetles are widespread in the forest belt of the Caucasus Mountains and were repeatedly found on leaves of various Heracleum species (Arzanov and Davidyan, 1996).

Two other curculionids are found regularly on H. mantegazzianum, but these also feed on other Apiaceae and related families. The larva of Liophleus tessulatus Müller feeds externally on the roots of H. mantegazzianum, but also on plants from other families. The adults are 7-12 mm long, feed on leaves (Sheppard, 1991) and are active during the night. Otiorhynchus tatarchani Reitter is polyphagous on many bush and tree species (Kryzhanovskij, 1974) and has root-feeding larvae. This species is found at altitudes of up to 1750 m a.s.l. L. tessulatus and O. tartarchani are able to breed parthenogenetically (Harde and Severa, 1981). The former species is present in western Europe, but the latter does not occur there.

The larvae of Phytoecia boeberi Ganglbauer (Cerambycidae) develop inside the stems or roots of giant hogweed. It has unknown host plant specificity, but other species from this genus are family-specific. We only found it in the Caucasus Mountains at the altitude of 1750 m a.s.l., where it was rather common in some localities. The females normally lay a single egg on the surface of a stem. The life cycle takes 1-2 years, with both adults and larvae overwintering inside the stems.

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