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View all mammal worksheets. View all marine life worksheets. View all insect worksheets. View all Bird worksheets. Insects, Spiders, Centipedes, Millipedes. Arthropods Arthropods are members of the taxonomic phylum Arthropoda, which includes insects, spiders, centipedes, millipedes and crustaceans. There are so many arthropods, it would be nearly impossible to compile a complete list. Experts say there may be 5 million species of arthropods worldwide -- most still unidentified.
Arthropods are some of Catoctin Mountain Park's most strange and fascinating organisms. Cicada Photo by John and Teresa Walther Insects Insects are invertebrates because they don't have a vertebral column backbone. Spiders, mites and ticks are all arachnids that can be found in Catoctin Mountain Park.
Unlike insects, arachnids have eight legs and no antennae or wings, and their body is divided into two main segments: A cephalothorax and abdomen.
The black widow spider is the only native Maryland spider whose venom can be dangerous to people. Many arachnids are considered to be beneficial, feeding on insects that many people consider to be pests. Centipedes are long, thin arthropods with one pair of legs per body segment.
As far as humans are concerned, this liquid is fairly harmless, usually causing only minor effects on the skin, the main effect being discolouration but other effects may also include pain and itching. Most millipedes lack a waxy layer on the outside of their exoskeletons, or hard outer coverings, that helps to prevent the loss of body moisture.
Like centipedes, millipedes spend most of their time in cool wet places and become active only at night or after it has been raining. Males and females usually have to mate to produce offspring, with males usually depositing sperm directly into the reproductive organs of the female.
There may or may not be any courtship behaviour. Bristly millipede males must first spin a web on which they deposit their sperm.
The female then approaches the web and puts the sperm into her own reproductive organs. In some pill millipedes a male attracts a female to mate with squeaking noises made by rubbing the bases of his legs against his body.
He then grasps the females body with his legs. A sperm packet is released behind his head and passed back from one pair of legs to the next, until it reaches the reproductive organs of the female.
In other pill millipedes the male covers the sperm packet in dirt before passing it back with his legs to his mates reproductive organs. Millipedes lay their eggs in the soil. Some species make individual cases for their eggs out of chewed-up leaves. In some species, the female, and occasionally the male, guard the eggs until they hatch. Although young millipedes resemble small adults, they are usually have no legs when they first hatch from the egg.
After they molt, or shed their exoskeleton for the first time, they have six body segments and three pairs of legs. So, how many legs do millipedes have? It depends on the group, and Hennen says it ranges between 24 and , at most. In fact, most millipede species have under legs.
Millipedes have some defensive mechanisms, but they don't bite or sting. They have very poor eyesight — some species have no eyes at all — and mostly just use antennae to find their way.
A millipede's best move when it feels threatened is to curl up in a ball, and secrete chemicals that ward off predators. The chemicals they secrete vary, but are released in such tiny quantities that they are generally not hazardous to humans. Some research describes how in certain tropical regions, monkeys actually seek out millipedes to use the chemicals they secrete as mosquito repellent.
Centipedes, by contrast, can bite using small fangs that secrete venom. Even then, while a centipede bite can be painful, it usually won't cause other harmful effects. Leg wise, centipedes' legs tend to spread out , while millipedes' legs point downward. Centipedes only have one pair of legs per segment, while millipedes have two pairs.
If you're not keen on getting close enough to check, Hennen says observe the creature's behavior. If it runs away quickly, it's likely a centipede. If it just curls up, it's probably a millipede. Scientists have developed new imaging techniques that use UV light to help them differentiate between millipede species.
This approach works because millipede exoskeletons and reproductive organs glow under UV light, as is the case with many other arthropods.
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