The Hexapod Clade (He)

See above. These animals have been very successful at exploiting almost every terrestrial and freshwater environment.

The Entognathan Clade

The base of the mouthparts is within the head capsule.

The Ellipura and wingless hexapods. The mandibles are simple and have a single articulation. The legs have a single tarsus which is not articulated. Tracheae may or may not be present. Colembolans (Figure 2) have an abdomen of six segments and proturans (Figure 3) have an abdomen of eleven segments. They have biting mouthparts and are scavengers and detritivores. Colembolans (Springtails) are sometimes very abundant on and near the water of calm pools where they can appear as dust that suddenly springs away when disturbed.

The Dipluran Clade

The Diplura are small wingless hexapods that have no eyes, no external genitalia, and no Malpighian tubules. Mandibles are simple with a single articulation and they work with a rolling action. The abdomen has eleven segments when embryonic, but fewer when they mature. Gonopores on are on the ninth segment. They have seven pairs of styli and one pair of cerci, and up to seven pairs of abdominal spiracles. They, too, have biting mouth parts and are scavengers in humus and moist areas. Misof et al. (2014) place this group as sisters to the insects.

The Insects (In)

The insects are hexapods in which the second maxillae have fused and become modified to form a labium, which functions almost as a lower lip. Also, they have lost all of their abdominal appendages.)

The Archaegnathan Clade

The archaegnathans (Jumping bristletails) are wingless insects with both ocelli (text with tooltip) An ocellus (ocelli, pl.) is a simple eye or eyespot characteristic of many invertebrate groups. and compound (text with tooltip) A type of eye characteristic of most arthropods. It is made of many individual simple ommatidia (ommatidium, sing.), each of which is like a simple eye with a lens and light-sensitive cells. eyes, which are contiguous. The body is scaly. The mandibles have a single articulation, and the tarsi have three articulated segments. Some legs are not uniramous (text with tooltip) Uniramous (adj.) means single-branched or unbranched. It usually refers to the unbranched leg of insects and other arthropods. in that they have exites. The abdomen has small appendage-like structures as well as caudal filaments. This group is sister to all other insects.

The Dicondylian Clade (Di)

These insects have mandibles with a double articulation and tarsi with five articulating segments. The mouthparts are ectognathous, they emerge from the head capsule. The head has a clypeus, a fused segment that makes up the face of an insect and articulates with the labrum (the upper lip), and small maxillary palps.

The Zygoentoma Clade

The Zygoentoma (Silverfish) is a group of wingless insects. The abdomen has eleven segments with three to eight pairs of styli. The eleventh abdominal segment is divided into articulated cercal filaments of equivalent length. The female gonopores are on the eighth segment, and male gonopores are on the tenth segment. They have no ocelli, and the compound eyes are reduced. They have no specific copulatory organs. The tracheal system is complex, with longitudinal trunks. They continue to molt after they have matured.

The Pterygota Clade (Pt)

The pterygota is a clade of insects that have two pairs of wings as adults (unless they have become secondarily lost). One pair of wings occurs on each of the second and third thoracic segments. They have no abdominal styli except on genital segments. Female gonopores are on the eighth segment, and the male gonopores are on the tenth segment. Copulation occurs, and the female usually has an ovipositor. The eggs have an amnion and chorion (text with tooltip) The chorion is the tough covering of the insect egg, the mbryonic membrane that encloses the yolk and and amnion. , making them waterproof. They cease molting when sexually mature.

The wing was the great evolutionary innovation of the insects and likely is the basis of their diversity and success.

Paleoptera

This group includes only two orders: Odonata (dragonflies and damselflies, Figure 6) and Ephemeroptera (mayflies, Figure 7). Both groups are very different from each other, but that is likely because they are remnants of an early radiation in the Carboniferous Period (Misof et al. 2014). Indeed, the characters that they share (aquatic larvae and an inability to fold the wings back) likely are plesiomorphic. Misof et al. (2014) did recover a weak association of the two orders

Neoptera (Ne)

These insects have wings that can fold back over the body.

Polyneoptera

These insects include Zoraptera (ground lice), Plecoptera (stone flies, Figure 8), Dermaptera (earwigs, Figure 9), Orthoptera s.s. (crickets and katydids, Figure 10), Mantophasmatodea (gladiators), Grylloblattodea (ice crawlers), Embioptera (webspinners), Phasmatodea (stick and leaf insects), Mantodea (praying mantis), Blattodea (cockroaches), Isoptera (termites). Many of these orders were once placed within a larger Orthoptera taxon (all underlined taxa); however, because termites emerge as sisters to the cockroaches, such an order would become paraphyletic. The monophyly of the Polyneoptera has been confirmed by Misof et al. (2014 and Wu et al. 2014).

Condyloptera

These are the Hemiptera (the true bugs, Figure 11) and Thysanura (thrips). Both of these groups have sucking mouthparts and their monophyletic relationship was confirmed by Misof et al. (2014).

Psocodea

These are the bark and true lice. Misof et al. (2014) recovered a strong association with the Holometabola (those taxa that undergo complete metamorphosis). Thus, lice, which do not exhibit complete metamorphosis, may be the sister group to all holometabolous insects.

Holometabola

These are the insects that undergo complete metamorphosis. They include several very successful orders: Hymenoptera (sawflies, wasps, bees and ants, Figure 12), Raphidioptera (snakeflies), Megaloptera (alderflies and dobsonflies, Figure 13), Neuroptera (net-winged insects), Strepsiptera (twisted-wing insects), Coleoptera (beetles, Figure 14), Trichoptera (caddisflies, Figure 15), Lepidoptera (moths and butterflies, Figure 16), Siphonaptera (fleas), Mecoptera (scorpionflies), Diptera (true flies). These orders include the most successful animals on the planet, judged by their species diversity.