Minuscules

Araneae is the order of true spiders and are second only to mites for being the largest order in arachnids. There are about 49,800 species recorded till May 2021. In contrast to popular belief, not all spiders use their silk to make webs. They use their silks in other elaborate ways, such as making guidelines, pheromone trails, making egg sacs, floating in the air for dispersal, etc. Some members of this order have some fascinating traits, a few of which are discussed here. Peacock spiders (Genus: Maratus) are famous for their striking colours and their complex courtship display. Unlike typical spider webs, Net-casting spiders (Family: Deinopidae) construct stretchable nets and cast them on their prey. Spiders of the genus Portia show remarkable intelligence through their hunting strategies. The jumping spider Toxeus magnus secretes milk-like liquid to feed its young.

Distribution and habitat: They are present everywhere globally except the polar regions. They have adapted to nearly all kinds of habitats. Urban habitats have suited certain spiders so well that they have become one of the common pests. Even though there are no aquatic spiders, the genus Dolomedes (aka fishing spiders) consists of semi-aquatic spiders that prey on insects, small fishes and tadpoles.

Feeding habits: The vast distribution of spiders is possible due to their generalistic feeding habits. They feed on insects, other spiders and other invertebrates. In some situations, they are also known to cannibalize. Rarely, some giant spiders also feed on small vertebrates like frogs, lizards, birds and bats. Orb-weavers (Family: Araneidae) are omnivorous, which feed on pollen too(2) . The species Bagheera kiplingi is the only spider that has a primarily herbivorous diet.

Evolution: Fossil records of Araneae are rare due to their soft body. Much of the fossil evidence of Araneae’s ancestors come from amber. It is a distinctive order in arachnids as they don’t have the abdominal segmentations that other arachnids have, and the ancestors of Araneae had. Ancestors of spiders had up to twelve segments, while spiders have only five. Even these five segments are fused, and the segmentation is not visible externally(3) . They are also unique from other arthropods due to their ability to produce silk, even as adults.

Life cycle: Females lay their eggs in sacs woven with silk. Females of the majority of species die following this. However, females of some species are known to guard the sac. The spiderlings, apart from their size and reproductive structures, resemble the adults. In the majority of the species, the spiderlings are independent but there are cases where the female nurses them or the female is fed upon by the spiderlings. They grow by moulting several times, similar to other arthropods. They reach sexual maturity after their final moult, following which they stop feeding and utilize all their energy to find a mate. Following mating, males either die or get eaten by females.

Ecological importance: Nasty and rarely deadly bites of a few spiders have gained a bad reputation for all spiders. As a result, their importance to ecology and to us fails to reach the common. They regulate the population densities of invertebrate herbivores and predators. Could you believe that it is estimated that one spider can eat 2,000 insects in just a year? Due to this broad appetite, they are crucial to their communities and in regulation. Humans benefit from some species (like Evarcha culicivora and Paracyrba wanlessi) as mosquitoes are a significant part of their diet. Hence, they directly reduce the chances of diseases spread by mosquitoes, viz. Zika virus, West Nile virus, Malaria, etc. They also act as natural pest controllers in crops by hunting aphids, grasshoppers, leafhoppers, beetles, and caterpillars. Reductions in pest abundance by spiders have led to decreased crop damage, which can help increase yields. Apart from that, spider silk has enormous utility to humans. However, it is used very scarcely as it is hard to extract it in industrial quantities. Researchers are working to solve this problem and have also succeeded to a certain extent. Researchers are also working on the potential use of spider venom as bio-insecticide and in treating ailments like stroke and cancer.