Adult and Larval Plant Range and Preference in Timarcha lugens (Coleoptera: Chrysomelidae): Strict Monophagy on an Atypical Host

We investigated the host range and preference of the high-mountain species Timarcha lugens Rosenhauer, an insect species with highly mobile larvae, testing the degree of specialization and the correlation between larval and adult preference for host plant. All 720 larvae, 1,035 adult females and 994 adult males, censused in the field over 3 yr (1997-1999) and in 20 populations located along all the distribution area of the species were living on one single host plant, Hormathophylla spinosa Kuepfer (Cruciferae). This differs from other Old World Timarcha, which are adapted to feed on Plantaginaceae and Rubiaceae. Laboratory experiments confirmed these observational results; all 130 beetles tested fed only on H. spinosa, and no beetle accepted any other plant species either in choice or nonchoice experiments. Larval and adult preference proved identical, both stages selecting only H. spinosa. We suggest that T. lugens has evolved the ability to attack an atypical host.