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These minute arthropods are apterous, unlike some orders of insects that have lost their wings secondarily (but are derived from winged ancestors). Their mouthparts are enclosed within a pouch in the head capsule, called the gnathal pouch, so only the tips of the mandibles and maxillae are exposed beyond the cavity. [1]
Here, the vertex, or the apex (dorsal region), is situated between the compound eyes of insects with hypognathous and opisthognathous heads. In prognathous insects, the vertex is not found between the compound eyes, but rather where the ocelli are normally found. This is because the primary axis of the head is rotated 90° to become parallel to ...
Differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After moulting, i.e. shedding their exoskeleton, the juvenile arthropods continue in their life cycle until they either pupate or moult again.
An instar (/ ˈ ɪ n s t ɑːr / ⓘ, from the Latin īnstar 'form, likeness') is a developmental stage of arthropods, such as insects, which occurs between each moult (ecdysis) until sexual maturity is reached. [1] Arthropods must shed the exoskeleton in order to grow or assume a new form. Differences between instars can often be seen in ...
Paired, mobile, and segmented, they are located between the eyes on the forehead. Embryologically, they represent the appendages of the second head segment. [8] All insects have antennae, however they may be greatly reduced in the larval forms. Amongst the non-insect classes of the Hexapoda, both Collembola and Diplura have antenna, but Protura ...
The subphylum Hexapoda (from Greek for 'six legs') or hexapods comprises the largest clade of arthropods and includes most of the extant arthropod species. It includes the crown group class Insecta (true insects), as well as the much smaller clade Entognatha, which includes three classes of wingless arthropods that were once considered insects: Collembola (springtails), Protura (coneheads) and ...
In general, arthropods have mouthparts for cutting, chewing, piercing, sucking, shredding, siphoning, and filtering. This article outlines the basic elements of four arthropod groups: insects, myriapods, crustaceans and chelicerates. Insects are used as the model, with the novel mouthparts of the other groups introduced in turn.
The mandibulates are divided between the extant groups Myriapoda (millipedes & centipedes, among others) and Pancrustacea (including insects and crustaceans, among others). Molecular phylogenetic studies suggest that the living arthropods are related as shown in the cladogram below.