What is a characteristic of leafmining insects?

Leafmining insects are specifically adapted to feed within the leaf tissue of plants. This characteristic is crucial because it allows them to access the nutrients found in the mesophyll, the inner tissue of leaves, while being protected from many external threats such as predators and weather. By burrowing into the leaf, these insects create distinctive mines or tunnels, which can often be observed as discolored or distorted areas on the leaf surface.

The other choices describe traits that do not accurately reflect the behavior or impact of leafmining insects. For instance, if they lived only on the surface of the leaves, they would not be considered leafminers. Resistance to pesticides may apply to some insect species, but it is not a defining characteristic of leafminers as a group. Furthermore, leafmining insects do affect plant health. The damage they cause can lead to impaired photosynthesis and overall plant vigor, which can impact plant health negatively.