Insect Orders: Odonata, Orthopteroid, Blattodea, Mantodea

Pterygota: Evolution of Winged Insects

• Pterygota, or winged insects, are divided into two main groups: Endopterygota and Exopterygota.
• Division into Endopterygota and Exopterygota is based on the developmental patterns of the wings and metamorphosis.

Endopterygota

• Insects in this group develop their wings internally as part of their complete (holometabolous) metamorphosis.
• Holometabolous development includes egg, larva, pupa, and adult, with each stage morphologically distinct.

Exopterygota

• Insects in this group have wings that develop externally as part of their incomplete (hemimetabolous) metamorphosis.
• These insects undergo gradual transformations, and immature forms (nymphs or naiads) resemble adults but lack fully developed wings.

Hemimetabolous Insects

• Paleoptera, such as mayflies and stoneflies, cannot fold their wings and hold them upright or spread outward when at rest.
• Neoptera can fold their wings back over their bodies when not flying.

Order Ephemeroptera (Mayflies)

• The name Ephemeroptera comes from the Greek words ephemeros ("living for a day") and pteron ("wing"), referencing the short adult lifespan.
• Mayflies undergo a subimago stage, which is a winged but sexually immature stage that molts into the adult stage (imago).
• Mayflies exhibit both incomplete metamorphosis and the ability to molt after acquiring full wings.
• Life cycle: egg, naiad (aquatic nymph), subimago, and imago (adult).
• Mayflies are important to aquatic ecosystems, and their larvae are a key food source for aquatic predators.
• These insects are characterized by triangular heads, strongly developed eyes (especially in males), multi-segmented antennae shorter than the head, and degenerate adult mouthparts.
• Forewings are generally larger then hindwings, the membranous wings feature a complex network of cross-veins.
• The reduced prothorax and synthorax support the functionality of the wings.

Order Odonata (Dragonflies and Damselflies)

• The name Odonata comes from the Greek words odous (tooth) and gnathos (jaw), referencing the modification of their labium.
• These distinctive insects have large, prominent compound eyes that are often color-patterned and provide a nearly 360-degree field of vision, small and inconspicuous antennae, and mouthparts specialized for capturing prey.
• Adults are characterized by large, membranous wings, with the synthorax (fused meso- and meta-thoracic segments) supporting a rigid thorax for flight muscles.
• Abdomens are cylindrical and elongate with visible segments.
• The life cycle includes an aquatic nymphal stage (naiad) followed by the emergence of winged adults.
• Odonates undergo true metamorphosis, molting to the adult stage after the subimago.
• Suborders: Zygoptera (damselflies), Anisoptera (dragonflies), and Anisozygoptera (a small and less-diverse suborder).

Orthopteroid Group of Insects

• This includes orders with mandibulate mouthparts, such as Orthoptera (grasshoppers, locusts, crickets, and katydids) and Blattodea (cockroaches).
• Common features include tegmina (thickened forewings), hindwings with large anal area and jugal lobe, exopterygote wing development, paurometabolous metamorphosis, and the presence of cerci at the tip of the abdomen.

Order Blattodea (Cockroaches)

• Cockroaches are characterized by a dorsoventrally compressed (flattened) body and hypognathous head that is inflexed and not freely movable.
• The prothorax is highly enlarged and movable, forming a shield-like pronotum (protergal shield) that overlaps the head and covers wing bases posteriorly.
• They have sclerotized forewings and membranous hindwings, the radial sector of the hindwings has numerous pectinate branches, and the hindwings are typically folded fanlike when not in use.
• Eggs are laid in oothecae (hard, sclerotized cases).
• Some species exhibit ovoviviparity.
• Cockroaches are primarily omnivorous and nocturnal and some species are pests, such as Periplaneta americana, and vectors of human diseases like Salmonella and Polio.

Order Mantodea (Praying Mantids)

• The name Mantodea refers to the praying posture, where the forelegs are raised in a raptorial position.
• They exhibit freely movable heads and slender necks, enabling a wider view for scanning for food, feed on other insects and spiders.
• The prothorax is elongate with a narrow and freely movable pronotum.
• Forelegs are modified into raptorial legs for seizing prey, the femur and tibia are heavily spined on opposite sides, forming a femora-tibial region.
• Spines (shape, arrangement, number) are characteristic in distinguishing groups within Mantodea.
• Wings consist of thickened forewings (tegmina) and membranous hindwings, which are fanlike when folded.
• Costa vein is strongly developed and subcosta vein is short and unbranched.
• The first radial (R₁) vein and radial sector near base of wing run as parallel unbranched veins to the base of the wings.
• Mantids are predatory and used as biological control agents.
• The eggs are laid in oothecae, produced from a frothy secretion that hardens into a protective capsule.

Order Phasmida (Stick and Leaf Insects)

• Phasmida, or stick and leaf insects, have camouflage abilities to blend into their surroundings.
• Their movements are sluggish, and their diet is vegetarian. Most species lack wings, but when present, forewings are opaque and tough (tegmina), acting as shields.
• Bodies can be cylindrical (stick-like) or flattened (leaf-like).
• The prothorax is much shorter than the meso- and meta-thoracic segments.
• All 3 pairs of legs are similar, slender, long, and adapted for walking slowly.
• Eggs are laid singly or in groups, but not in oothecae.
• Many species exhibit parthenogenesis.

Order Orthoptera (Grasshoppers, Locusts, Crickets, and Katydids)

• The name comes from the Greek words ortho (straight) and ptera (wing).
• These insects are commonly referred tos grasshoppers, locusts, crickets, and katydids.
• Their head is hypognathous, and the anterior part often projects beyond the eyes to form a fastigium.
• The prothorax is large, often with lateral lobes.
• The forewings are leathery (tegmina).
• The upper surface of the pronotum can be flat or saddle-shaped, and may be crested.
• Hindwings are membranous and broader.
• Orthopterans produce stridulation sounds for communication.
• Pro- and meso- thoracic legs are generally similar.
• They are characterized by strong, saltatorial hind (metathoracic) legs with thickened femurs for jumping.
• This order contains two suborders: Ensifera (long-horned grasshoppers, crickets, and katydids, with more than 30 segments in the antennae) and Caelifera (short-horned grasshoppers, with fewer than 30 segments in the antennae).
• In Orthoptera, hindwings are much broader and have a large anal area.
• The costa vein is sub-marginal in the forewings in contrast to mantids and blattids.
• In the hindwings the costa is marginal, the cubitus bifurcates near the wing base, the hindwing has numerous veins.
• Females are recognized by the presence of an ovipositor, while males have an enlarged 9th abdominal sternum containing the genitalia. Orthopterans are mostly phytophagous, but some are omnivorous or predacious.
• Eggs are laid singly or in batches, held together by proteinous materials, and are used to cement soil to form egg pods.
• Pests found in Orthoptera belong to the superfamily Acridoidea of the suborder Caelifera, which includes Locusta migratoria, Schistocerca gregaria, Zonocerus variegatus, and Oedaleus senegalensis.
• Orthoptera exhibit phase polymorphism (solitary forms or gregarious forms (locusts) that form swarms when there is high population density).

Order Isoptera (Termites)

• The name Isoptera means "equal wings" (iso – equal and ptera – wing).
• Fore and hindwings are equal, membranous, and similar in size, shape, consistency, and texture.
• The wings lack cross veins.
• Mouthparts are mandibulate with a large basal plate (gulamentum) on the labium.
• The external genittalia is rudimentary or absent.
• They have a social organization with 3 castes: reproductives, soldiers, and workers.
• Reproductives are divided into primary (macropterous (fully winged) that lose their wings after their nuptial flight) and secondary (neotenics, and are either brachypterous (reduced wings) or apterous (no wings)).
• Soldiers are known as mandibulates and nasutes.
• Mandibulates have strongly mandibles with defensive capabilities, cutting and slashing to defend.
• Nasutes have vestigial mandibles and spray a sticky, toxic liquid.
• Workers are apterous, lack eyes, and maintain the nest, care for the royal pair and the soldiers.
• They generally feed on wood and materials containing cellulose, and this is digested by bacteria in their guts. Termites are responsible for timber damage, they are important in soil biology, and they help decompose organic matter. Examples include foraging termites, wood harvesters, fungus growers, and grass harvesters.

Order Dermaptera (Earwigs)

• These are the earwigs, usually confused with Japygidae of Diplura because of the forcep-like cerci at the end of their abdomen, which are used in defense and mating.
• This feature also cause confusion with staphylinidae (Coleoptera).
• The head is prognathous, broad, and flattened, vertex usually bears ecdysial suture and the labium has a distinct gula.
• Some are winged and wingless.
• Forewings are short and thickened to form the tegmina without defined veins.
• Hindwings are semi-circular, have remigium reduced and sclerotized, the vanus is enlarged and has a unique pattern of venation, and the anal area has 3 veins and a network of cross veins and intercallaries.
• Each abdominal segment is elongated to about 1/3 of its length.
• The cerci are modified into forceps-like structures, nocturnal, thigmotactic, and the female shows maternal care of young ones until they reach early developmental stages.
• Hemimerridae in Africa and Arixeniidae in Asia are ectoparasites of banana rats and bats.

Order Grylloblattodea (Ice Crawlers)

• Grylloblattodea is a small order with only a single family, Grylloblattidae.
• The their head is flattened and prognathous, mandibles are sickle shaped, and the galea are 2 segmented.
• Insects are apterous, elongate, and cryptozoic, inhabiting cold environments such as caves or icefields.
• The first abdominal segment bears an eversible sac.
• Third segment bears a pair of long sensory cerci.
• Their diet consists of dead insects and mosses.

Order Plecoptera (Stoneflies)

• These are the stoneflies, soft bodied and fragile and their antennae are long.
• The head is prognathous and broadly sessile on the prothorax.
• Compound eyes are well developed and 2/3 the prothorax is quadrangular in shape.
• Both fore- and hindwings are membranous, and the hindwing anal area is expanded.
• The radial and median sectors are fused, radius and cubitus shows unilateral pectinate branching.
• Adults frequent streams and nymphs are aquatic.
• This order exhibits hemimetabolous development and is important in freshwater food webs, nymphs prey for fish. Development of tracheal gills for respiration.

Order Embioptera (Webspinners)

• Embioptera, or webspinners, are characterized by silk-producing glands on their forelegs, produce silk tunnels, and are typically encountered in the tropics.
• The Head is prognathous, tarsi are 3-segmented while basitarsus of the foreleg is a globular glandular structure with silk glands.
• They are gregarious and sub-social, silken structures shelter and are a mechanism for foraging.
• The female show maternal care of young ones.

Test your knowledge of insect orders including Odonata, Orthropteroid, Blattodea, and Mantodea. This quiz covers nymph identification, synthorax function, vision, shared features, oothecae function, wing structure, head adaptation, and ecological roles.