Abstract
In Mediterranean habitats, the specialist butterfly Euphydryas aurinia oviposits on Lonicera implexa. Previous work has shown that ovipositing females select and lay a higher number of egg clusters on certain plants. In this paper the results of a field study aimed at assessing whether females use plant size and/or plant or leaf greenness (i.e., chlorophyll concentrations) as cues for oviposition are described. Size of plants did not appear to be an important factor in determining host plant selection, probably because even small plants provide enough resources for the young larvae to reach the diapausing stage and because last instar larvae, the most likely to face resource depletion, can move great distances in search of food. Measurements of both spectral reflectance and chlorophyll concentration of plants failed to reveal differences between host and non-host plants. On the other hand, reflectance and chlorophyll concentration of leaves were found to be important in oviposition choice as egg clusters were generally located on the greenest leaves with the highest chlorophyll contents. This suggests that females use visual cues to select the leaves that will provide optimal growth opportunities for newly hatched larvae. Although there was some indication that plants receiving a greater number of egg clusters also had more leaves of high chlorophyll content, multiple egg batches on single plants could also be a consequence of females being attracted by the presence of conspecific egg clusters.
Highlights
Euphydryas butterflies (Lepidoptera: Nymphalinae: Melitaeini) have been the subject of much ecological research (Ehrlich & Hanski, 2004)
No significant differences in plant size were found between plants receiving and not receiving egg clusters (Mann-Whitney U-test: Z = 0.44, P = 0.66), or between the two plants with several and those with only one egg cluster (U-Mann Whitney test: Z = 0.44, P = 0.77) (Fig. 1)
That several E. aurinia egg clusters can be laid on a single plant of L. implexa (e.g. Singer et al, 2002) was confirmed once again by our data
Summary
Euphydryas butterflies (Lepidoptera: Nymphalinae: Melitaeini) have been the subject of much ecological research (Ehrlich & Hanski, 2004). One of the central themes underlying these issues is the fact that Euphydryas species lay eggs in clusters of several to many dozens, a strategy that has important implications for their population biology and the searching behaviour of females. It has been suggested that the choice of egg-laying sites may be important for batch-layers since females make just one or only a few decisions, which will have great repercussions on offspring survivorship. In line with this argument, the discrimination phase in searching Euphydryas and other Melitaeini females is much longer than in most butterflies that lay eggs singly
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