Insects

An organism that has the general morphological 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 obvious effusion.

2. It has three pairs of legs (hence the term hexapods), each pair arising from one of the three primitive thoracic segments (the prothorax in front, the mesothorax in the middle, and the metathorax in the back), which are badly defined at the top. species.

3. It has two pairs of wings, one derived from the mesothorax and the other from the metathorax. The wings may be rudimentary or absent in some species.

4. It has a pair of antennae that project anteriorly from the head segment.

5. Their mouthparts are designed to bite or suck.

6. Your abdomen is often similarly composed, featuring longitudinal segments, the terminal of which is modified to include the reproductive tract and in some cases a stinger.

The subclassification of insects is based mainly on an evaluation of the wings, the parts of the mouth and the type of metamorphosis of the organism.

1. The wings can be present or absent. There are species differences in consistency, shape, and size between the front and rear wings. Venation (arrangement of supporting ribs) of the wings is the most important identifying feature.

2. The parts of the mouth can be adapted to bite or suck. Species can be identified on the basis of structural differences in each of the parts of the mouth and their juxtaposition with each other.

3. To reach adult size and development, the immature insect undergoes one or more changes at different stages.

Metamorphosis

Primitive metamorphosis: the least change, with newly emerged young looking similar to 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 the wings or other appendages gradually increase to adult size. Complex (complete) metamorphosis – The newborn insect does not resemble the adult, although careful examination reveals internal anatomy that is clearly insecticidal – the fly worm is one example. An additional stage, the pupa, is required for the organism to achieve the profound physiological and structural changes between larvae and adult forms.

Although the medical technologist is rarely asked to examine the internal structures of insects, it is interesting to know that they are highly developed despite their relatively small size. The nervous system consists of a chain of interconnected ventral nerve ganglia. The respiratory system is made up of a fairly elaborate network of branching tracheal tubes that open directly to the outside as tiny pores in the cuticle, filling virtually all internal cells with air. Detecting these structures can help differentiate insect larvae from small nematodes. With a magnifying glass or dissecting microscope. tracheal tube openings 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 in the front and an anal canal in the back. The pharynx, esophagus, stomach (or midgut), intestine, and rectum can be identified under the microscope. In bloodsuckers, the pharyngeal musculature is well developed, so it acts as a pump or siphon.

The genitals are also well developed; include a pair of tests and seminal vesicle in the male; ovaries, oviduct, seminal receptacle and ovipositor in the female. Four orders of insects of particular medical importance are: Siphonaptera (fleas), Anoplura (lice), Hemiptera (bed bugs) and Diptera (flies and mosquitoes).