The photoreceptor processes that view in an anterior
direction in the anterior stemma and in a posterior direction
in the posterior stemma are all thin, whereas they
are thick in regions of the retina that view above the head
in both stemmata. The functional meaning of such difference
is not known. If an object of a given size approaches
the burrow of a larva, and keeps its height constant, its
apparent size will be small at low elevation, and become
maximal when it is above the larva’s head. The small photoreceptor
processes that view the periphery or at low elevation
may therefore match these smaller image sizes. This
may result in the stimulation of similar numbers of photoreceptor
cells regardless of the position of the object. In the
present study the corneal lens and the retina have been
examined morphologically and optically in the posterior
large stemma of the tiger beetle larva with special reference
to the distinct visual behavior of the larva. The optical
properties and retinal structure we have obtained may be
related to the visual behaviors for which they provide the
input, but the neural connections and physiological
response properties of the underlying neural apparatus will
require further analysis in order to validate the ideas proposed
in the present study.