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Generalized insect head: Anterior aspect VERTEX coronal suture ocular suture compound eye dorsal ocellus antennal suture subocular suture antenna frontal suture GENA FRONS clypeus anterior tentorial pit mandible labrum subgenal suture epistomal suture Suture lines: lines of weakness associated with molting flexible region as in wing hinge of Schistocerca (locust) flexible region as in wing base of Lepidoptera epicuticle exocuticle endocuticle epidermis flexible region lacking exocuticle (membrane) fibrous protein resilin plus chitin lamellae pure resilin wedge of partially sclerotized “mesocuticle” ecdysial cleavage line or suture (lacks exocuticle) 1 Generalized insect head: Posterior aspect VERTEX coronal suture occipital suture compound eye GENA OCCIPUT (occipital area) postoccipital suture ocular suture remnants of head somites? cervix (neck) foramen magnum mouthpart region (mouthparts removed) Generalized insect head: cockroach (Dictyoptera: s.o. Blattodea) Blattodea 2 Head articulations and muscles extrinsic muscles condyles condyles Mandible – Antenna – monocondylar (monocondylic) extrinsic muscle condyle condyle (antennifer) dicondylar (dicondylic) tentorium adductor (flexor) muscle abductor (extensor) muscle Md point of articulation (condyle) (sagittal plane) Head shape I: the effect of Muscles [Note sexual & caste dimorphism] (a proctotrupoid parasite of woodboring beetle larvae) vertex Mandible muscles tentorium sclerotized, flattened “tendon” exodont mandibles brain Vanhornia larva – Soldier ant – huge abductors huge adductors Atta clypeus cibarium clypeus labrum Cicadidae “soldier” sucking mouthparts Pharyngeal/cibarial pump muscles clypeus Thysanoptera (thrips) 3 Head shape II: Compound eyes Stemmata and Dorsal Ocelli Lateral ocelli (stemmata) Dorsal ocellus Dorsal ocelli larva of Lepidoptera (Holometabola/ Endopterygota) adult (or nymph) of Cicadidae (Hemimetabola/Exopterygota: Hemiptera) Head shape: Extreme effect of eyes antenna Odonata (s.o. Anisoptera) antenna Diptera (a) antennae Neuroptera (Ascalaphidae) Aeschnidae (Odonata) (also sexually dimorphic) antenna Diptera (b) Diopsidae (Diptera – a) 4 Other modifications of the compound eye Odonata male Strepsiptera Thysanoptera Gyrinidae (Coleoptera) male male Ephemeroptera Ephemerida water surface Ascalaphidae (Neuroptera) Sexual dimorphism: Ascalaphidae (Neuroptera) Male and female Drosophila (Diptera) Simple eyes: Stemmata and Dorsal Ocelli Stemmata and Dorsal Ocelli Lateral ocelli (stemmata) larva of Lepidoptera (Holometabola/ Endopterygota) • • Dorsal ocellus Dorsal ocelli adult (or nymph) of Cicadidae (Hemimetabola/Exopterygota: Hemiptera) Dorsal ocelli are commonly lost (even whole orders). Compound eyes usually retained, but lost in cavernicolous species. 5 Structure of the Antenna nerve fibers Johnston’s Organ antennal suture socket PEDICEL antennifer SCAPE FLAGELLUM (with annuli separating the antennomeres) intrinsic muscle nerve bundle extrinsic muscle OR: antennifer Lost in some endoparasites (Strepsiptera females) and ectoparasites (plant lice: Sternorrhyncha) Culicidae (Diptera) scale insect (Coccidae) Modifications of the antennae: filiform moniliform setaceous clavate capitate serrate lamellate pectinate flabellate pedicel geniculate plumose pedicel aristate pedicel • • stylate • • (pedicel with Johnston’s Organ) tactation (touch) mechanoreception (vibration & sound, e.g. mosquitoes) chemoreception (e.g. moths) prehension (sexual selection) 6 pectinate (Lepidoptera) aristate (muscoid Diptera) geniculate (Formicidae) Modifications of the antennae flabellate (Coleoptera) clavate (Lepidoptera) 1 2 34 5 6 I 7 II III ‘Trignathous’ insect mouthparts procephalon plus somite 1 2 3 4 6 5 7 --- THORAX --I III II procephalon plus somites 1, 2, 3 4 postoccipital suture labrum mandible (2) 5 6 7 I II III labium (4) maxilla (3) 7 Trignathous mouthparts: Back view Lateral view pharynx salivary duct labium maxilla mouth cibarium clypeus preoral cavity labrum mandible labrum salivarium labium hypopharynx clypeus LABRUM abductor and adductor muscles MANDIBLE molar area point of articulation MAXILLA incisor area cardo LABIUM stipes palpifer submentum lacinia galea maxillary palp postmentum Note ‘serial homology’ of maxilla and labium mentum prementum labial palp glossa paraglossa HYPOPHARYNX suspensory sclerite lingual sclerite 8