WHAT IS AN INSECT EXTERNAL ANATOMY GROWTH AND DEVELOPMENT INTERNAL ANATOMY & PHYSIOLOGY
Body divided into three regions HEAD the head capsule is a sturdy compartment that houses the brain, a mouth opening, mouthparts used for ingestion of food, and major sense organs (including antennae and compound eyes)
Insect Mouth Types Chewing & Biting Mouth Parts Usually found on predatory insects, and those that feed on vegetation Mandibles
Piercing & Sucking mouth parts Slender, tubular feeding and sucking organ used to extract nectar from flowers stabbing mouthparts used to extract fluids from plants and animals Mouth part is used as a sponge to suck up fluid proboscis
THORAX this region is almost exclusively adapted for locomotion contains three pairs of walking legs in many adult insects, one or two pair of wings composed of three body segments: prothorax, mesothorax, and metathorax
ABDOMEN segmented structure located just behind the thorax Spiracles (opening to the respiratory system) Digestive tract and male and female reproductive organs (genitalia)
EXOSKELETON serves as a protective covering over the body, also know integument Provides the surface for muscle attachment A water-tight barrier against desiccation Sensory interface with the environment MULTI-LAYERED STRUCTURE WITH FOUR FUNCTIONAL REGIONS: Epicuticle, procuticle, epidermis, basement membrane
EPIDERMIS primarily a secretory tissue formed by a single layer of epithelial cells Responsible for producing at least part of the basement membrane as well as all of the overlying layers of cuticle BASEMENT MEMBRANE Supportive bilayer that serves as a backing to the epidermis Effectively separates the hemocoel (insect s main body) from the integument
PROCUTICLE Lies immediately above the epidermis Contains microfibers of chitin surrounded by a matrix of protein In some parts of the body, procuticle stratifies into hard, outer exocuticle and a soft, inner endocuticle Sclerotization occurs after each molt in which a chemical process causes the protein matrix to solidify forming rigid plates of exoskeleton known as sclerites Membranes are areas that remain soft and flexible and sclerotization does not occur because of higher amounts of resilin, an elastic protein
EPICUTICLE Outermost part of the cuticle Functions to reduce water loss and block invasion of foreign matter EXOCRINE GLANDS Specialized epidermal cells Large, secretory cells produce compounds such as pheromones and repellants
MICROTRICHAE (PILE) Tiny, hair-like projections MACROTRICHAE (SETAE) Larger hairs, bristles, and scales SKELETAL MUSCLES Attach to the inner surface of the integument
MORPHOGENESIS All changes that involve growth, molting, and maturation Molting -periodic outgrowing and replacing of the exoskeleton Growth of wings Development of genitalia
METAMORPHOSIS Insects lives are divided into a series of stages: egg, one or more immature stages, and adult In most cases, the appearance of a given species changes drastically in each successive stage. The process by which one stage transforms into another is called, metamorphosis
WITHOUT METAMORPHOSIS ORDERS Thysanura Microcoryphia Insects undergo little, or no structural change as they grow older Immatures are called young (similar to adults in every way except size and sexual maturity)
insects exhibit gradual changes in body form immatures are called nymphs or if aquatic, naiads maturation of wings, external genitalia, and other adult structures occurs in small steps from molt to molt developmental changes that occur are visible externally as the insect grows, but adults retain the same organs and appendages as nymphs (eyes, legs, mouthparts) *aquatic immature stage GRADIAL METAMORPHOSIS ORDERS Orthoptera Blattodea Mantodea Phasmida Isoptera Dermaptera Embioptera Pscoptera Phthiraptera Hemiptera Odonata* Plecoptera* Ephereroptera*
COMPLETE METAMORPHOSIS ORDERS Thysanoptera Neuroptera Coleoptera Mecoptera Trichoptera Diptera Siphonaptera Hymenoptera Lepidoptera Insects have immature forms (larvae) that are very different from adults Larvae are adapted mostly for consuming food and growing in size While larvae will molt several times gaining size (instar), they do not acquire any adult-like characteristics When fully grown, larvae molt to an immobile pupal stage (pupa) and undergo a complete transformation Larval organs are digested internally and are replaced with new adult structures The adult stage, which usually bears wings, is mainly adapted for dispersal and reproduction
Caterpillars go through 5 stages of growth. Each stage is called an instar. When the caterpillar becomes too large for its skin, it molts. A caterpillar will molt 5 times before it becomes a chrysalis (pupa)
ENDOCRINE SYSTEM Comprised of hormone secreting structures that help maintain homeostasis, coordinate behavior, and regulate growth, development, and other physiological activities. Hormone- a chemical signal sent from cells in one part of an organisms to cells in another part (or parts) of the same individual Produced in small quantities but cause profound changes
DIGESTIVE AND EXCRETORY SYSTEM Insects use their digestive system to extract nutrients and other substances from the food it consumes. Insects have a complete digestive system occurring in a tube-like enclosure, the alimentary canal, running lengthwise through the body from the mouth to anus Ingested food only travels one way Insects have salivary glands residing in the thorax
CIRCULATORY SYSTEM Insects, like all athropods have an open circulatory system where is hemolymph (blood) spends much of its time flowing freely within body cavities where it makes direct contact with all internal tissues and organs Responsible for movement of nutrients, salts, hormones, and metabolic wastes throughout the insects body It plays several critical roles in defense Seals off wounds through a clotting reaction It encapsulates and destroys compunsd that provide a degree of protection against predators It can cool the body by conducting excess heat away Dorsal vessel is the major structural component of an insect s circulatory system
RESPIRATORY SYSTEM Insects are aerobic organism (they must obtain O2 from their environment Responsible for delivery sufficient O2 to all cells of the body and for removing CO2 that is produced as a waste from the circulatory system In most insects, the respiratory system us separate from the circulatory system Tracheal system- is a complex network of tubes that deliver oxygencontaining air to every cell in the body Air enters through the spiracles and to the tracheal system
REPRODUCTIVE SYSTEM Reproductive organs of insects are similar in structure and function to those of vertebrates A male s testes produce sperm; a female s ovaries produce eggs (ova) Some species of insects are able to reproduce by parthenogenesis, a from of asexual reproduction in which new individuals develop from unfertilized egg Advanced insects exhibit internal fertilization where males deposit their sperm inside a female s body
THE NERVOUS SYSTEM Insects have a relatively simple nervous system with a dorsal brain linked to a ventral nerve cord Nervous system is a network of specialized cells (neurons) that serve as the information highway within the body Neurons are divided into three categories, depending on their function within the nervous system Afferent (sensory) neurons Efferent (motor) neurons Internuncial (association) neurons Side view of body showing relative position of circulatory (yellow), digestive (green), and nervous (blue) systems