correct but there are more names to describe the stage. Pupa is a general term that is always correct for this stage, whereas, cocoon refers to a type of pupa. Knowing the pupal type (Figure 21) will give you some idea as to what to expect when the adult hatches from the pupa. o Insects with obtect pupal forms have the appearance that their appendages are “glued” to the body within the pupal case. The pupa may be protected within a cocoon. Lepidoptera and some Diptera have this pupal type. o The appendages are “free” in exerate pupal forms. These pupae resemble a mummified adult. They are not covered by a cocoon. This is probably the most common pupal type of insects that undergo complete metamorphosis. However, Lepidoptera and Diptera will not have this form.
Figure 21: Obtect (top-left), Exerate (top-right), and Coarctate (bottom) pupae.
o The coarctate form is similar to the execrate pupa, but the appearance is different in that the pupa is covered with a hardened cuticle. Therefore, it does not have the appearance of a mummified adult. Diptera often have this pupal type.
Insect Senses We touched on some of the senses that insects have, but it is important to realize that the world we share with insects is perceived differently by the different insects and by us. Most of the sensory components are located on the antennae and legs, but insects can have sensory organs in places that we cannot imagine. In some cases, there are structures that appear to be sensory in nature, but for which the function has eluded entomologists. An interesting case in point is the Noctuid moths. Many male Noctuids find females ready to mate by following a pheromone trail well below our threshold of detection. Often, these same moths can hear the ultrasonic “radar” of bats (fearsome nocturnal moth predators) with their abdomen and take appropriate a c t i o n s . Probably they see wavelengths of light we can’t, and taste chemical differences in plants of the same species. Some bees can sense the Earth’s electromagnetic field. Many insects have the ability to see polarized light and others have the ability to track time. It is not that we are not
Entomology
Page 17