Ecological Entomology (2013), 38, 155–163 DOI: 10.1111/een.12001 European checkerspots (Melitaeini: Lepidoptera, Nymphalidae) are not aposematic – the point of view of great tits (Parus major ) MONIKA TESA ˇ ROV ´ A, 1 ZDEN ˇ EK FRIC, 1,2 PETR VESEL ´ Y, 1 MARTIN KONVI ˇ CKA 1,2 and R O M A N F U C H S 1 1 Department of Zoology, University of South Bohemia, ˇ Cesk´ e Budˇ ejovice, Czech Republic and 2 Department of Ecology and Conservation Biology, Institute of Entomology, Biology Centre Czech Academy of Sciences, ˇ Cesk´ e Budˇ ejovice, Czech Republic Abstract. 1. Checkerspots (Melitaeini, Nymphalidae, Lepidoptera) are usually considered a textbook example of aposematic butterflies and several studies on Nearctic species confirm this. 2. The responses of the avian predator, the great tit (Parus major L., Paridae, Passeriformes), to five species of Palaearctic checkerspots and one control palatable ringlet (Aphantopus hyperanthus L., Satyrinae, Nymphalidae, Lepidoptera) were observed. 3. None of the tested checkerspots was attacked more often than the control palatable ringlet, which suggests that birds originating from the wild had no previous bad experiences with them. Nonetheless, certain tested butterfly species (Melitea didyma , Esper; Melitea aurelia , Nickerl, and probably Melitea athalia , Rottemburg; Melitaeini, Nymphalidae, Lepidoptera) elicited some aversion in great tits (a long time handling them, a small portion of the body eaten, and some discomfort after ingestion). 4. Larvae of commonly eaten species (Melitea diamina , Lang; Euphydryas aurinia , Rottemburg; Melitaeini, Nymphalidae, Lepidoptera) feed on plants containing secoiridoids (in contrast to the earlier mentioned protected species, which feed mostly on plants containing iridoid glycosides); therefore the efficiency of secoiridoids in the chemical protection of butterflies is discussed. Key words. Euphydryas , Melitaea , Parus major , unpalatability, warning signal. Introduction Checkerspots (Melitaeini: Lepidoptera, Nymphalidae) are a well-studied example of aposematic butterflies (e.g. Bowers, 1980, 1981, 1983a, 1993). It has been shown that their chemical defence arises mostly from the sequestration of the secondary metabolites of their host plant (usually iridoid glycosides – Bowers, 1983a; Jensen, 1991) in the larval stage. In contrast to other butterfly species (Bowers & Puttick, 1986, 1989; Bowers, 1993, 2003), these chemicals have been shown to be preserved into the adult stages in checkerspots (Bowers, 1980, 1981, 1993; Bowers & Puttick, 1986). In some species of the genus Euphydryas (e.g. E. anicia , Doubleday, 1847), Correspondence: Petr Vesel´ y, Department of Zoology, University of South Bohemia, Braniˇ sovsk´ a 31, 37005 ˇ Cesk´ e Budˇ ejovice, Czech Republic. E-mail: petr-vesely@seznam.cz the ability to transform some sequestered chemicals (catalpol esters) into iridoid glycosides has been confirmed (Stermitz et al ., 1986; Gardner and Stermitz, 1988). In addition to iridoid glycosides, other chemicals usable in antipredatory defence (secoiridoids) have been identified in checkerspots (Wahlberg, 2001). These chemicals do not seem to be sequestrated from the food of caterpillars, but are produced de novo (Bowers & Williams, 1995). Several North American representatives of the tribus Meli- taeini have been proven to elicit avoidance in avian predators. Naïve blue jays (Cyanocitta cristata L., Passeriformes, Corvi- dae) showed lowered attack rates on Euphydryas chalcedona (Doubleday), and Euphydryas editha (Boisduval). Euphydryas phaeton (Drury) even elicited discomfort and vomiting in these predators (Bowers, 1980, 1981). Similarly, Euphydryas anicia was refused by grey jays (Perisoreus canadensis , L., Passeriformes, Corvidae) while Euphydryas gilletti (Barnes)  2013 The Royal Entomological Society 155