Venomous Animals


CENTIPEDES

Centipedes (Latin: hundred, legs) belong to Phylum Arthropoda, Subphylum Myriapoda, Class Chilopoda. They are elongated, dorsoventrally flattened, metameric animals with one pair of laterally attached legs in each body segment.

They have a pair of venomous claws which are modified maxillipedes that are used for defence as well as for hunting small insects and worms. Their bites may have effects ranging from mild discomfort to life threatening to man. Their narrow extended body is made up of anything between 15 to 150 or more segments, depending on the species and individual, with each segment bearing a pair of legs.

The head carries a pair of long, sensitive antennae and, in addition to small chewing mouthparts, a pair of large, strong claw-like structures which close together like tongs just below the head and are equiped with poison glands. Centipedes are carnivorous and use their poisonous head-claws to seize and paralyse their prey. They hunt, mostly at night, for arthropods and other invertebrates such as insects, spiders and worms, although some of the very large tropical species (the so called Giant Centipedes, in some cases up to 25 cm long) also attack small vertebrates. Many of the larger centipedes have an unpleasant bite and the poison of some giant species can be dangerous to humans, especially children.

Centipedes normally have a drab coloration combining shades of brown and red. Scolopendromorphs have bright aposematic colors. Size can range from a few millimeters in the smaller Lithobiomorphs and Geophilomorphs to about 30 cm in the largest Scolopendromorphs. Scolopendra gigantea, found in Amazonian forests is the largest existing species of centipede in the world, reaching over 30 cm in length. It is known to eat bats, rodents and spiders.

Worldwide there are about 3,000 described species. Centipedes are found in an array of terrestrial habitats from tropical rainforests to deserts. Accordingly, they are found in soil and leaf litter, under stones and in deadwood logs. In addition, centipedes are among the largest terrestrial invertebrate predators and often they contribute a significant proportion to invertebrate predatory biomass in terrestrial ecosystems.

There are five orders of centipede: Craterostigmomorpha, Geophilomorpha, Lithobiomorpha, Scolopendromorpha, and Scutigeromorpha.

Males deposit a spermatophore for the female to pick it in her genital chamber. They lay their eggs singly in holes in the soil, which is filled with soil and leaves. In some species,15 to 60 eggs are laid in a nest in the soil or in rotten wood and the female stays with the eggs, guarding and licking them to protect them from fungi and predators. In anamorphic development, as in Scutigera, nymph hatches from egg with only 4 pairs of legs and in successive moults grows additional 5, 7, 9, 11, 15 pairs of legs. In orders Geophilomorpha and Scolopendromorpha, development is epimorphic, in which all legs are fully formed when the larvae hatch from eggs and offspring do not develop more legs between moults.

Scutigera, which habitually lives inside houses and other buildings, usually in slightly damp places such as cellars and basements, is called House Centipedes, which generally grows to about 3 cm long and differs from other centipedes in having very long, delicate legs,usually 15 pairs, with the hind pair extremely long and thin. They also have very long antennae and compound eyes. In warm climates they can survive outside, living in caves and rocky places. They are very fast runners and prey on flies, cockroaches and other insects. House Centipedes can inflict a painful bite.

CONTROL

Controlling centipedes and millipedes outdoors includes removing objects that provide harborage such as trash piles, rocks, boards, leaf piles, compost piles and similar materials. Spraying or dusting diazinon, malathion, carbaryl, propoxur (Baygon), pyrethrin may provide some control. Inside houses cracks, crevices or other hiding places such as under clothes washers and dryers may be sprayed with the above-mentioned insecticides. Contact pesticides, such as propoxur or pyrethrins may be sprayed directly on centipedes for quick control. Carbaryl or diazinon granules may be used on turf.

WASPS

Insects known as wasps include the parasitic wasps and the stinging wasps of family Vespidae. About 75,000 species of wasps are known, most of them parasitic or predators. Almost every pest insect species has at least one wasp species that is a predator or parasite upon it and hence wasps are increasingly used in biological pest control.

Wasps are characterized by two pairs of membranous wings, three pairs of legs and an ovipositor (tube for laying eggs) that may be modified as sting in sterile females. The abdomen is narrowly attached to the thorax by a petiole. In addition to their compound eyes, wasps also have three simple eyes known as ocelli, arranged in a triangle on the top of the head. Males do not have a sting. Females have diploid (2n) number of chromosomes and develop from fertilized eggs. Males are haploid (n) and develop from unfertilized eggs.

Yellow jackets and paper wasps prey on caterpillars and other larvae that can destroy crops. Wasps feed on flower nectar and play a role in pollination. Wasps can be solitary or colonial and social insects. Adult solitary wasps generally live and operate alone and may or may not construct nests, whereas social wasps exist in colonies numbering up to several thousand strong and build nests.

The type of nest produced by wasps can depend on the species and location. Many social wasps produce paper pulp nests on trees, holes in the ground or in other such sheltered areas. By contrast solitary wasps are generally parasitic or predatory and do not build nests at all. Unlike honey bees, wasps have no wax producing glands. Many instead create a paper-like substance primarily from wood pulp, which is gathered locally from weathered wood that is softened by chewing and mixing with saliva. The pulp is then used to make combs with cells for brood rearing. Mud daubers and pollen wasps construct mud cells in sheltered places typically on the side of walls. Potter wasps similarly build vase-like nests from mud, often with multiple cells, attached to the twigs of trees or against walls

Wasp sting

The sting is essentially a hollow tube through which the venom is squirted once the tube has inserted into the skin of victim. The sting has evolved from the ovipositor of the female. The sting of a wasp is rather like two swords lying parallel to one another in a sheath. Each sword has backward-pointing barbs like a fish hook. The wasp thrusts one of the swords into the victim’s flesh, and uses it as an anchor to drive the second sword past it and in deeper. The second sword is anchored in turn to push the first sword further in. It all happens within a second, and once the sting is embedded well into the victim, venom is pumped into the puncture wound. A wasp sting will normally deliver 3 to 15 mg of venom. The venom is stored in a venom sac in the abdomen, which when squeezed by curling up the abdomen delivers its load through the sting very rapidly in less than 0.3 seconds.

In contrast to the bee, the wasps and hornets can insert and withdraw their sting with ease. The single wasp is therefore able to deliver multiple stings with ease. The volume of venom delivered by a wasp sting is much less than that delivered by a bee. Depending on the type of wasp the volume can range from as little as 2 micrograms to as much as 15 micrograms.

It should be remembered that the sting apparatus itself consists of a venom sac, which contains the venom, and a redundant egg laying tube which acts rather like the needle on a hypodermic syringe. This needle allows the wasp to curl up its abdomen, squeeze the venom from the sac into the sting apparatus, and inject the venom into the poor victim. Another feature unique to the wasp and hornet is that the venom contains a pheromone which alarms all other wasps in the area and invites them to join the attack on the victim.

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