In biology, all organisms are classified according to a taxonomic system that comprises a number of hierarchical levels.
This section provides information on the main orders of insects and arachnids that can be found in the forest environment.
Here is the taxonomic system that has been adopted for this site, with an example corresponding to each hierarchical level:
You can go through the section using the taxonomic levels: class, order, family and species. You will be able to identify a number of specimens based on the main morphological characteristics of adults.
Class : Arachnids (Arachnida)
Arachnids have four pairs of jointed legs. Their body consists of two parts: the cephalothoraxand the abdomen (in some orders, these two parts are fused).
Mites and ticks are among the best known members of the order Acari (e.g., spruce spider mite).
- Very small, sometimes microscopic, arthropods with an oval or elongated body.
- Unsegmented abdomen, which is often attached to the cephalothorax (fused head and thorax).
- The adult has four pairs of legs, although some have only two or three pairs.
- The mouthparts, called chelicera, are adapted for piercing, sucking and lacerating.
Class : Insects (insecta)
Insects possess three pairs of jointed legs. Their body is divided into three distinct parts: the head, the thorax and the abdomen.
Ground beetles, lady bird beetles, junes beetles and long-horned beetles are among the best known members of the order Coleoptera (e.g., whitespotted sawyer).
- These insects bear four pairs of wings. The forewings, called elytra, serve as a protective shield (hence the word "Coleo-ptera" which means "Shield Wings"). The two elytra are hard, veinless covers that join in the middle of the abdomen along a central line but do not overlap. They often cover the hind part of the abdomen, though they may also be fairly short. At rest, the membranous hindwings are folded beneath the elytra. These wings are generally designed for flight.
- The shape of the antennae is highly variable.
- The mouthparts are designed for chewing.
Black flies, mosquitoes and houseflies are among the best known members of the order Diptera.
- These insects have a single pair of wings (hence the name "Di-pthera").
- The modified hindwings are reduced to a pair of balancing organs called halteres.
- The shape of the antennae varies.
- The mouthparts are adapted for sucking, piercing and sucking or lapping. In some species, they are atrophied.
Plant bugs (e.g., chinch bug) are among the best known members of the order Heteroptera.
- These insects have two pairs of wings, the forewings are sclerified, or hardened, at the base and membranous at the apex(toward the anus). At rest, the membranous portions of the forewings lie flat and overlap on the abdomen. The hindwings are completely membranous. A few species are apterous (wingless) or >brachypterous (having rudimentary, nonmembranous wings).
- The mouthparts are adapted for piercing and sucking, and the rostrum rises anteriorly on the head.
Scale insects, aphids and cicadas are among the best known members of the order Homoptera.
- These insects have two pairs of wings, which form a roof-like structure at rest. The forewings and hindwings have a similar shape and similar venation (hence the name "Homo-ptera").
- The forewings are uniform in texture; they are folded diagonally or overlap partly on the abdomen. Many species are apterous.
- Very short, hair-like antennae.
- The mouthparts are designed for sucking or piercing and sucking, and arise posteriorly on the head, seeming to come from between the anterior coxa (base of legs under the abdomen).
Wasps, bees and ants are among the best known members of the order Hymenoptera.
- These insects have two pairs of membranous wings. Most species have forewings with many cells. In some small species, the cells are reduced in number or may be completely absent.
- The hindwings are markedly smaller than the forewings; a row of small hooks (hamuli) along their front edges anchors them to the forewings.
- Robust and compact body, with an abdomen that is usually constricted at the waist (wasp waist).
- Variably shaped antennae, shorter than the body, claviform (club-shaped), elbowed or threadlike.
- The mouthparts are primarily designed for chewing or for chewing and lapping. In bees, which are adapted for chewing and lapping, the mouthparts form an elongated structure (proboscis) designed for sucking nectar from flowers.
Butterflies, moths and caterpillars are among the best known members of the order Lepidoptera (e.g., spruce budworm).
Morphological characteristics (adult):
- These insects have four membranous wings that are covered with scales; a few species are apterous or have vestigial wings.
- Body and legs covered with hairs, the abdomen is composed of ten segments.
- Antennae with numerous segments, typically threadlike, club-shaped or feathery.
- The mouthparts are adapted for sucking and usually include a coiled tubular proboscis. Few species have atrophied mouthparts (a few Microlepidopterans). Only one family has mouthparts that are designed for chewing (Micropterygidae).
Thrips (e.g., pear thrips) are among the best known members of the order Thysanoptera.
- These minute insects (less than 2 mm) have an elongated, spindle-shaped body and two pairs of long, slender wings that have reduced or absent venation and that are fringed with small hairs, hence the name "Thysano-ptera". A number of species or forms are apterous(wingless).
- Short antennae and legs.
- The asymmetrical, piercing-sucking mouthparts form a conical leak with three stylets (sharp, rigid protuberance).
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