left | Anthrenus

scrophulariae (Dermestidae)

This adult hide beetle

from Europe shows the

ocellus, or “third eye,”

in the center of its head.

below | Rhinostomus

barbirostris (Curculionidae)

The Neotropical Bottle

Brush Weevil has dense

bristles on the male

rostrum, which are

used in courtship.

of limb-like sensory organs called maxillary and

labial palps, which taste and process food.

Mandibles may be only for eating, or they may

be developed for hunting and defense, as in many

Carabidae, or for display, as in male stag beetles

(Lucanidae). In most weevils (Curculionoidea) and

a few other families (some Lycidae, Salpingidae)

the mandibles are placed on a beaklike extension

of the head called a rostrum.

Probably the most important sensory structures

of the head in beetles are the antennae. We do not

have a directly equivalent sense, and we often refer

to them as “feelers,” but the sense that they

provide is much closer to smell than to touch.

Many beetle antennae, especially in males, are

lamellate or pectinate to maximize surface area so

that they can detect small quantities of chemicals

in the air, for example pheromones produced by

the female. The importance of antennae is shown

by the fact that many adult beetles have lost their

eyes, but none have lost their antennae. The

original beetle ground plan includes 11 segmented

antennae, but in a few families and genera some

segments have been lost, or in a few cases, some

more gained. The shape and structure are

important taxonomically.

Finally, in some beetles, for example in

Scarabaeidae, the head has horns, which may

connect with horns on the thorax.