Arthropod Collection and Indentification Techniques
The subclass Insecta contains two divisions, Exopterygota and Endopterygota, depending upon whether the wings are developed internally or externally. Furthermore, the Exopterygota includes insects with wings that develop externally AND have simple metamorphosis. ENote: In some classification systems Pterygotan orders are further subdMded into Paleoptera and Neoptera, based on the ability to flex wings over the abdomen. Members of the paleopteran orders (Ephemeroptera, Odonata) lack a wing-flexion mechanism and are unable to move wings posteriorly over the abdomen.] Orders of Exopteugotes include the following.
5.3.1 Exopterygota 6. Ephemeroptera (Ephemerida, Plecoptera) Emayflies] 7. Odonata [dragonflies, damselflies] 8. Orthoptera [grasshoppers, locusts, katydids, crickets] Metamorphosis (Greek, meta = change off morphosis = form) is another feature ofpterygote insects that is important to understand, but difficult to define in a way satisfacto U to everyone. Entomologists typically use the term in a restrictive sense to mean the morphological and physiological changes from the immature to the adult insect. Anatomical change is achieved through molting. Metamorphosis may be gradual, as during the transition of structure within a stage, such as the nymphs of a bug. Metamorphosis may be radical, as seen between stages, such as the transition from a caterpillar to a butterfly. Molting serves at least two purposes: growth in size and change in shape. When viewing all insects and their close relatives, we can see trends in the expression of metamorphosis. For instance, amotaloolous (Greek, a = without; metabole = change) development involves organisms that lack metamorphosis. Specifically, ametaboly is applied to the Apterygota in which the adult closely resembles the immature stages. Ametabolv is viewed as the primitive condition among hexapods. Pauromotabolous (Greek, pauros = little; metabole = change) development refers to metamorphosis in which the changes of form between immature and adult are gradual and inconspicuous. Paurometabolous insects are terrestrial. Examples of paurometabolous insects include Dermaptera, Orthoptera, Embiidina, Isoptera, Zoraptera, Corrodentia, Mallophaga, Anoplura, Hemiptera, and most Homoptera. The situation is not straightforward, as noted below. Hemimetabolous (Greek, hemi = halfi metabole = change) development refers to metamorphosis in which form changes between immature and adult are made in one radical move. The anatomical changes between stages are conspicuous. Hemimetabolous development involves aquatic immamres because most hemimetabolous insects are aquatic as immamres. Examples of hemimetabolous insects include Plecoptera, Ephemeroptera, and Odonata. Holometabolous (Greek, holos = entire; metabole = change) development involves the interpolation of a pupal stage between immature and adult. This is the most advanced type of metamorphosis found among the Insecta. Examples include Neuroptera, Coleoptera, Strepsiptera, Trichoptera, Lepidoptera, Mecoptera, Siphonaptera, Diptera, and Hymenoptera. Fitting all of the Insecta into one metamorphic category or another is difficult because exceptions occur.
Until recently, the Blattodea and Mantodea were considered suborders of an order called the Dictyoptera. The following orders were included with the Orthoptera for many years: