subject: Medical Arachnoentomology- General information about the insect family [print this page] Insects Insects
An organism having the general morphologic characteristics of an arthropod can be classified as an insect if the following criteria are met:
1. It has three distinct segments- head, thorax, and abdomen-with no evident effusion.
2. It has three pairs of legs (thus the term hexapods), each pair arising from one of three primitive thoracic segments (the prothorax in front, the mesothorax in the middle, and the metathorax posteriorly), which are ill defined in the higher species.
3. It has two pairs of wings, one arising from the mesothorax and one from the metathorax. Wings may be rudimentary or absent in some species.
4. It has one pair of antennae projecting anteriorly from the head segment.
5. Its mouth parts are designed for biting or sucking
6. Its abdomen is composed often similar-appearing the longitudinal segments, the terminal one of which is modified to include the reproductive apparatus and in some cases a stinger.The sub-classification of insects, is based primarily on an assessment of the organism's wings, mouth parts and type of metamorphosis.
1. Wings may be present or absent. There are species differences in the consistency, form, and size between the fore and hind wings. The venation (arrangement of the supporting ribs) of the wings is the most important identifying characteristic.
2. Mouth parts may be adapted for either biting or sucking. Species can be identified on the basis of structural differences in each individual mouth parts and their juxtaposition one to another.
3. In order to attain the size and development of the adult, the immature insect undergoes one or more changes in distinct stages.Metamorphosis
Primitive metamorphosis: the least change, with the newly emerged young appearing similar to the adult except in size.
Simple (incomplete) metamorphosis: Three stages are recognized: the egg, the nymph, and the adult. During the nymph stage, the developing organism undergoes a series of molts, when wings or other appendages increase gradually to adult size. Complex (complete) metamorphosis: The newly hatched insect bears no resemblance to the adult, although careful examination reveals an internal anatomy that is distinctly insectile: The fly maggot is an example. An additional stage, the pupa, is required for the organism to accomplish the profound physiologic and structural changes between the larva and adult forms.Although the medical technologist is rarely called upon to examine the internal structures of insects, it is of interest to know that they are highly developed despite their relatively small size. The nervous system consists of a chain of interlinked ventral nerve ganglia. The respiratory system is composed of a rather elaborate network of branching tracheal tubes which open directly to the outside as minute pores in the cuticle, permeating virtually all the internal cells with air. Detecting these structures may aid in differentiating insect larvae from small nematodes. With a hand lens or dissecting microscope. the openings of the tracheal tubes can be identified in an insect larva; the cuticle of the roundworm is continuous. The circulatory system is simple: a pulsating system, representing a primitive heart, is located anteriorly and attached to a large blood-filled cavity (the hematocele) by a single vessel (the aorta. There is no network of blood vessels or capillary channels. The digestive system is complete, with an oral opening anteriorly and an anal canal posteriorly. Pharynx, esophagus, stomach (or midgut), intestine, and rectum can all be identified under the microscope. In the bloodsuckers, the pharyngeal musculature is well developed so that it acts as a pump or siphon.The genitals are also well developed; they include a pair of testes and seminal vesicle in the male; ovaries, oviduct, seminal receptacle, and ovipositor int he female. Four orders of insects of particula medical importance are: the siphonaptera (fleas), the Anoplura (lice), the Hemiptera (bugs), an the Diptera (flies and mosquitoes).I am Funom Theophilus Makama. I advertise through writing. As a platinum expert Author, I write lots of articles and hence promote interested websites, companies, groups, organizations, and communities through publishing and distributing my articles. For more information on this interesting venture, click on the link below:http://funom-makama.blogspot.com/2010/07/advertising-contracts.html
Medical Arachnoentomology- General information about the insect family
