Insects are the most diverse group of animals that are found in most environments. In the Animal kingdom, Insects are in the Phylum Arthropoda; Arthropods have an exoskeleton of chitin that they shed as they grow; they also have segmented bodies and jointed appendages. In addition to the Class Insecta, the Arthropoda also includes the arachnids (spiders and mites), myriapods (ex. centipedes), and crustaceans (crabs, lobsters, etc.). Insects are distinguished from the other Arthropod classes by the following features:
As adults and in some species in the juvenile stages, insects have three body parts: the head, thorax, and abdomen. Although in some insect species, some of the three body parts are fused together and may be difficult to distinguish. See this website for images and more discussion of insect anatomy: Purdue University, College of Agriculture, Department of Entomology, 4-H and Youth: Insect Anatomy [1]
Browse the following websites for two major agricultural crop pests. What kind of organisms are they? In what stage of their lifecycle do they cause the most damage to the crop plants?
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Insects may be herbivores or omnivores. Herbivorous insects may eat plants by directly feeding on plant tissues such as leaves or roots. Herbivorous insects include caterpillars, beetles, grasshoppers, and ants. Some insects pierce plants and suck plant nutrients from the plant vascular system, typically the phloem, (the cells that transport plant carbohydrates and amino acids); although some insects feed on the xylem, the vascular cells that transport water and nutrients. Examples of piercing-sucking insects include aphids and mosquitoes. By contrast, butterflies and moths have siphoning mouthparts for drinking nectar. Omnivore insects consume multiple kinds of food including other insect prey and plant tissues such as leaves and/or nectar and pollen.
Although insect pests are major agronomic pests, only about 1% of insect species are agricultural pests. Insects also contribute to important ecosystem processes, including: i. pollination, ii. predation and parasitism (ex. lady beetles, lacewings, praying mantis, parasitic wasps); iii. decomposition of organic materials such as crop residues and manure (Ex. dung beetles) iv. providing food for other organisms, such as fish and birds. Review the photos below for some categories of beneficial insects, and some of their characteristics here: National Pesticide Information Center [6]
Read the following website: Omnivorous Insects: Evolution and Ecology in Natural Agriculture Ecosystems [9].
Then answer the following questions:
What did scientists observe happened to cotton plants and insect herbivores after cotton plants were injured by herbivorous insects?
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To conserve or maintain predatory insects, what is required? What can farmers do to attract and conserve predatory insects?
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Links
[1] http://extension.entm.purdue.edu/401Book/default.php?page=insect_anatomy
[2] http://ento.psu.edu/extension/insect-image-gallery/honey-bees/general-honey-bee-images
[3] https://askabiologist.asu.edu/incomplete-metamorphosis
[4] http://extension.entm.purdue.edu/fieldcropsipm/insects/corn-rootworms.php
[5] https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/pests-and-diseases/cotton-pests/cotton-pest-identifcation
[6] http://npic.orst.edu/envir/beneficial/table.html
[7] https://creativecommons.org/licenses/by-sa/2.0
[8] http://www.troutnut.com
[9] https://www.e-education.psu.edu/geog3/sites/www.e-education.psu.edu.geog3/files/Mod8/Krimmel%202011-Omnivorous%20Insects_%20Evolution%20and%20Ecology%20in%20Natural%20and%20Agricultural%20Ecosystems%20_%20Learn%20Science%20at%20Scitable.pdf