Ent1LectInsectCommunication2008

Ent1LectInsectCommunication2008 - Making Sense of the...

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Unformatted text preview: Making Sense of the World: How Insects Use Their Senses & Insect Communication Lecture Goals • How do insects sense the world around them? • What are the tools of the insect sensory world? • Introduction to insect communication Insect Nervous System, the Senses and Functional Segmentation A. B. A. Side view of stylized insect body, nervous system is blue. B. Dissected nervous system viewed from the top of the insect. Note the highly segmented nature of the nervous system. 1 How do insects sense the world around them •Vision (simple and compound eyes) •M h i l senses Mechanical •touch •sound •Chemical senses •smell •taste Vision •Simple eyes or Occelli → do not sense color → sense differences in light and dark •Found on top of the head between the compound eyes Vision See images at 100 frames/second (humans = 15 frames/second). Fast flying insects evolved this system to cope with high speed flight in complex environments. Sensitive to color (detects UV environments. light, but not the far red spectrum) 2 Mechanical Sensations: Touch Scanning electron micrograph (150X), shows a single sensory hair that acts as a touch receptor Hairs on the insect body act as touch receptors. When the insect touches an object with the hair, OR something touches the hair, it bends, deforming the membrane at its base which is connected to a nerve. A section of such a hair is shown on the right. --graphics --graphics from Alien Empire, p. 50 3 Mechanical Sensations: Touch •Hairs serve as touch receptors. •Touch receptors are used in communication with other insects and to sense the physical environment. •Special touch receptors are sensitive to vibrations transmitted through whatever surface the insect is on, eg. planthoppers produce a eg. low frequency “song” that transmits as vibrations through plant stems and leaves (NOT AIRBORNE). Mechanical Sensations: Sound •The perception of sound = perception of airborne vibrations. •Humans hear a limited range of frequencies (20 to 20,000 Hertz). Insects hear in the range of 1 to 100,000 Hertz ( (although each species hears in a narrow range within this). g p g ) •Insect hearing involves a special touch receptor that is sensitive to airborne vibrations. •This touch receptor is a membrane attached to clusters of special cells that connect to an auditory nerve. This nerve translates vibrations into nerve impulses that are conducted to the group of nerves in the insect head that we call the brain. Mechanical Sensations: Sound •We call the touch receptor for detecting sound the insect ear. The exact position of the ear varies with species, but may be on the legs, thorax, wings or abdomen. --graphics --graphics from Alien Empire, p. 54 -- from Intro to Insect Biology and Diversity, p. 134 4 Mechanical Sensations: Sound •Sound is key in the mating of many insects. •Specificity may be determined via a match between the female hearing range and the sounds made by singing males of their own species. p •The male of each species has its own specific song, so females of other species, even closely related ones are effectively deaf to them. •This system has the advantage of being transmitted over considerable distance while allowing communication to be very specific with your own species. Chemical Senses: Smell and Taste •Insects have a highly sensitive sense of smell. •The antennae hold the principal organs of smell. •Scent is a very important means of communication and the sensory structures on the antennae are geared to detect airborne molecules as well as those laid down on a solid surface. •Although they are very sensitive, insects respond to a narrow range of scents that are relevant to their behavior. Thus, chemical communication can be very private and useful over large distances. •Insects use scent to communicate to potential mates, warn members of their species of danger and in social insects to communicate about food, caste and colony status. Chemical Senses: Smell and Taste Multibranching of antennae increases the receptive area for smell. 5 Chemical Senses: Smell and Taste •Chemicals for communication between insects of the same species = pheromones •Very small pheromone quantities, highly selective sensors in the antennae = responses to relevant scents •Versatile communication (mixtures and molecule orientation = secure, species specific communication) Questions: How do pheromones and hormones differ? What is meant by “relevant scents”? What is meant by versatile communication? Chemical Senses: Smell and Taste •Taste sensors (on or near mouthparts and/or ovipositor). •How do these sensors help insects to locate food plants? •How and for what insects do taste sensors benefit communication? Questions: What is trophyllaxis? What trophyllaxis? can humans learn from insect communication? Even the smallest among us…. • Communication in the world of thrips (Order Thysanoptera) – Male Leks – Territoriality 6 Summary •Insects use vision, touch, sound and chemistry to sense the world around them. •These senses are important to their ability to find mates, to defend themselves and to interact within a colony when social. •The sensory cues that a particular insect species detects are often narrow, thus, communication can be very species specific and operate over relatively large distances. Questions to Answer from the Film Clip •What are pheromones and how do insects use them to find mates? What kind of sense organs are used to detect pheromones? What are the advantages to using a pheromone in mate searching and recognition? •What moth fine-tunes the system using pheromones and finesound? Wh t i th advantage t adding a sound d? What is the d t to ddi d component to the communication? •What example is given regarding use of sound in communication? Why doesn’t this strategy disadvantage the insect with regard to attracting predators? •How does the jewel beetle use vision in identifying a mate? How have humans interfered with this communication? •How does the male walnut husk fly use touch in communication? 7 ...
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