Zoology

Apterygotes Primitve Insects Springtails Silverfish Hexapods Collembola



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Insects existed long, long time ago. They existed during the dinosaur’s reign in planet earth. There are a lot of different species of insects. There are those that live under the ground, others live under the stones and rocks. There are insects that eat plants and there are those that eat other insects. Let’s take a look at a very different type of insects. They are called apterygote insects.

The term apterygote came from Greek words meaning “without wings.” These are primitive, wingless insects and they hexapods which mean they have six legs. Some of them do not have eyes. Scientists believed that fossils found, occurred during the Devonian period that is 417-354 million years ago. They are small, agile and wingless even the present times and their evolutionary history. They have a direct areal gliding descent. It’s a preflight phenomenon from which insects are believed to have evolved winged flight capacities.

There are four major orders of Apterygote. The Collembola are also called the springtails. They are the largest among the modern hexapods and they are not considered to be insects any more.

Springtails are normally less than 6mm long. It’s either they have six or fewer abdominal segments and possess an appendage that is tubular in shape. Most of the species have an abdominal, tail-like appendage and it’s called furcula. It is folded beneath the body used for jumping when they are threatened. As the common names says, “springtails.”

The Protura or proturans are sometimes called “coneheads.” They have no eyes, wings and also lack pigments. Their colors are either white or pale brown. The first three pairs of their five segmented legs are for sensory functions. Their heads are shaped into cones.

Then there are the Dipluras which are also called the “two pronged bristletails.” They also do not have eyes and unpigmented. They have long antennas. They have ten or more segments forward from the head. They also have a pair of cerci, which is located from the last of the eleven abdominal segments. Cerci are either long or short pincer like. The name came from the Greek words “diplo,” or two and “uros,” or tail.

The last order are the thysanuras, included here are the silverfish and firebats. The term also came from Greek words “thysanos” or fringe and “oura,” for tail. It refers to the three filaments at the last segment of the abdomen. Their movements are just like the fish, it’s as if they are swimming. They have flat bodies and they have flexible antennae.

There are primitive features that other insects don’t have. First their younger stage, or nymphs, go through little or even no metamorphosis unlike butterflies. Their younger stage still resembles the adults. Their skin is thin making them translucent. Their males deposit sperm packages or spermatophores (it’s a capsule created by males of various animal species then transferred entirely to the female’s ovipae) rather than the female fertilizing inside. Some males deposit spermatophores on the ground and the females will be the ones to pick it up. They continue to moult or shed skin through life, with multiple instars. Their molting may take 40 to 50 times after reaching sexual maturity. They also possess small appendages called “styli,” on some abdominal segments.

http://www.cals.ncsu.edu/course/ent425/library/tutorials/systematics_taxonomy/apterygota.html


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