Lecture 4 - Ento 320 online PDF

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Lecture 4: External Anatomy Generalized Insect Body Plan  Head o Sensory o Consumption  Thorax o Locomotion  Abdomen o Internal Organs o Defense o Excretion Orientation  Anterior: the front / the head  Posterior: the back / the end of the body  Dorsal: the top (dorsal fin)  Ventral: underside  Apical/distal: further away from the body  Basal/proximal: closer to the body  Longitudinal axis: head to the rear  Lateral axis: runs from left to right Exoskeleton  Function o Structure and attachment o Protective o Conserves water  Composition o Sclerotized plates with membranous areas Chitin    

Nitrogen-containing polysaccharide Generally arrayed in cuticular protein layaer Principal component of the exoskeleton Sclerotization (hardening of protein matrix below epicuticle) occurs shortly after each molt

Exoskeleton: ecdysis  Must shed old cuticle to allow for new growth  Followed by hardening  All honey bee castes molt about every 24 hours during the first 4 days of larval life. They then molt a few more times in this pre-pupal stage

Exoskeleton: Composition  Cuticle o Epicuticle  Outermost part of cuticle  Reduces water loss anc blocks off foreign matter  Sclerotized  Cement layer  Protects from abrasion  Wax blooms  Chief barrier to water movement in and out of the insect’s body  Functions:  Communication  Thermoregulation  Water balance  Predator avoidance o Exocuticle o Endocuticle  Epidermis o Epideral cell o Gland cell o Basement membrane Spiracles  The spiracles are the openings in the exoskeleton for air exchange (respiration)  The abdomen is continually moving due to flexible membrane joints between segments  Movement helps in breathing, digestion, excretion, and circulation  Largest pair on thorax (next to wings)  Hairs to keep out dirt, dust Head  Major sense organs: o Compound eyes  Two compound eyes: 6,900 facets ea  Facet: lens of transparent exoskeleton that can “see” at a fixed focal length  Only fair vision: a bee “sees” by assembling a mosaic in the large optic lobes of the brain from hundreds of different facets  As the bee (and thus an object) moves, the view of each lens changes, improving visual ability  They distinguish patterns only if they are sufficiently different and image has enough brokenness  Bee Vision

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Trichromatic vision: blue, green and ultraviolet light (UV) Vision is shifted toward shorter wavelengths (300-650nm) Color Vision: Nectar guides Polarized Light: bees are able to navigate on cloudy days because they can detect polarized light

o Ocelli  3 “simple-lens eyes” arranged in a triangle  light sensitive organs on front dorsal surface of the head  assist bees with sun orientation during navigation  many pigment cells  cannot form an image  circadian rhythms  possibly orientation o Antennae  Each antenna has 12 segments  The scape (1st segment) is the longest and most flexible  Positioned halfway on the head, fits into a ball and socket joing  The pedicel (2nd segment) is a flexible elbow joint  The flagellum consists of the last 10 distal segments of nearly equal size  Antennae are use in olfaction  Antennae are covered with hairs, pits, pore plates, pegs and other sensory structures that perceive stimuli  Antennae are very mobile and in constant movement  Antennae smell, taste, perceive humidity and temperature, feel, monitor gravity and flight speed, and detect sound waves (vibrations) to help them cope with their daily routines o Mouthparts  Bees have chewing-lapping mouthparts: they can manipulate solids and lap up liquids  Four parts  Labrum (front-most): serves as protective shild closing the mouth cavity  Mandibles: “jaws” that move laterally, manipulate resources o Food manipulation  Ingest pollen  Cutting and shaping o Manipulation wax and propolis  Nest construction o Spoon-shaped  To feed brood and queen o Defense, grooming, carrying debris  Maxilla and labium have different parts, folding together to form the proboscis (tounge)

Proboscis is sucking tube with inner and outer chamber ending in the spoon-shaped labellum and glossa  Liquid ingestion (honey, water, nectar)  Exchange of liquids (trophallaxis)  Licking to transfer pheromones or for grooming  Pollen collection through dense hairs  Learning and memory test using taste reception with chemicals suspended. Proboscis extended to imbibe liquid after bee is stimulated with an odorant o Sensory hairs 

Caste Differences  Queen  Worker  Drone Thorax  Locomotor section of the body  Sclerotized to provide strength for muscle attachment  3 body segments: o prothorax o mesothorax o metathorax (last segment of thorax)  3 pairs of legs (6 total)  2 pairs of wings (4 total) Wings          Legs     

wings are paired, first pair largest each wing has numerous “veins” on the surface that carry blood and nerve signals veins create a network of cells and provide support to the wing during flight, both wings are joined by a set of hooks (hamuli) 230 beats/sec 24 km/hour (empty) forewing hamuli hindwing

3 pairs of legs, one per thoracic segment not only for locomotion but also contain sensory structures to taste, smell and feel work as a pair of triangles: 1st and 3rd leg of one side work with middle leg of the opposite side each pair of legs has special adaptations each leg has 5 major segments:

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o coxa o trochanter o femur o tibia o tarsus legs end in a pair of tarsal claws legs have body hairs modified for grooming

Fore Legs  fore legs have the antenna cleaner o indented area with special stiff hairs that clean the antennae Middle Legs  middle legs have a stout spine or spur used to spear wax scales from the abdominal wax glands to pass to the mandibles where it is shaped and positioned on newly build comb Hind Legs  hind legs are highly modified with hairs arranged in special patterns for pollen collection  the corbicula (pollen basket) carries pollen from flower to hive  the comb hairs collect and accumulate pollen  the rake and pollen press push and pack pollen Abdomen  the bee’s “wasp-waist” is the narrow segment that separates the first and second segments of the abdomen – propodeum  the abdomen lacks external attachments. The 7 visible (3 are hidden) abdominal segments consist of top (tergites) and bottom (sternites) plates  each abdominal segment has a pair of spiracles for respiration Stinger  a highly modified portion of the reproductive system is the worker bee stinger  in workers, the ovipositor has lost the egg-laying function, instead it is used for defense  muscles attached to the sting help drive it into the victim  tiny barbs on the 3 part shaft ensure that it stays in the victim so the alarm chemical remains at the sting site Queen vs Worker Sting...