Plasticity in resource use by the leafminer moth Phyllocnistis sp in response to variations in host plant resources over space and time

We examined how sedentary herbivorous insects cope with changes in resource availability with host plant phenology by studying the multivoltine lepidopteran leafminer Phyllocnistis sp. on the Japanese privet (Ligustrum japonicum). The privet offers three resources: primary shoots in the spring, lammas shoots later in the season, and older leaves. We examined the seasonal abundance of these resources and the density of mines in each to assess competition between leafminers at the tree, shoot, and leaf scale. The leafminer initially used leaves of primary shoots, then shifted to young leaves of lammas shoots, but never used old leaves. The relative scarcity of lammas shoots increased the density of mines, so the leafminers maximized their use of the intra-leaf microhabitat: they commonly preferred the lower surface of leaves, but came to use both surfaces. Thus the leafminer compensated for the lower availability of lammas shoots by maximizing microhabitat use.