Oviposition trials of Euphydryas phaeton on Plantago lanceolata

Understanding the circumstances under which insect herbivores will adopt a
novel host plant is a longstanding question in basic and applied ecology.
Though there has been ample study of regional differences in host
preference across numerous insect herbivores, the extent to which
intraspecific variation in plant species shape these patterns is
relatively less well known. In parts of its range the Baltimore
checkerspot Euphydryas phaeton uses English
plantain Plantago lanceolata, a novel host plant, in addition to
its native host, White turtlehead Chelone galbra. We
offered female butterflies from each region the non-native host lpant
sourced from both regions and compared their oviposition behavior. The
non-native host was near universally rejected by butterflies in the region
where only the native plant is used. In the region where both hosts are
used, plants from that same region were preferred relative to plants from
the other region. This suggests that regional variation in host plant use
by an insect depends on intraspecific variation in both species in the
interaction.