Spiders... your friendly neighborhood!

Ever since I was a small child, I've always been fascinated by spiders. These largely misunderstood creatures captured my heart when I saw them for the first time. From that point on, my curiosity took over and started reading about them anywhere anytime. While these arthropods scared me, they had a certain beauty and upheld themselves with such magnificence that always brought me back to them. Their natural hunting abilities and their usage of the webs they produce have always excited me and made me want to read more.

Spiders are invertebrates under the class Arthropoda. They are ubiquitous and found in every major biome present in nature. They are often referred to as generalist species as they feed on whatever prey they find. Arachnids follow what is told to be a three-prey species system to acquire the essential amino acids that are vital to their functioning. Spiders hunt in a variety of ways; some choose the sit-and-wait method of hunting which involves them waiting till their prey walks into their trap which when caught will be consumed. Some spiders choose to hunt on land such as wolf spiders or hunting spiders while some employ the element of surprise to capture their prey. While spiders are considered as generalist species, going so far as to feed on detritivores to ensure their survival, some specialize themselves to a single prey species. These spiders are specialists often controlling the prey population of a particular prey species, an example of this can be the ant-mimicking spider and the bolas spider (which imitates the female moth’s pheromone to attract male moths within its striking range). A cause of generalist feeding of spiders can be linked with food shortage or shrinking prey density. This polyphagous feeding ensures their survival and their continued life.

Hunting methods
Spiders are mostly known for their ability to build webs and use them for hunting and capturing prey, but there are some spiders who prefer hunting by using webs. On the basis of hunting, we can classify
spiders in two broad types; web- weaving and hunting spiders.

Web-weaving spiders are species of spiders which prefer to build webs and use them to their advantage when it comes to capturing prey. These species prefer to wait till their prey gets caught in their trap.

Orb-weaving spiders which belong to the family Araneidae build intricate web designs which they use to capture prey. The webs they create are the most organized. Most orb-weavers will use their webs
built in a concentric circle manner to capture their prey. The golden orb-weaver spider found in Australia builds its webs in the same concentric manner as most orb weavers do, but the golden orb weaver produces its silk which has a golden colour. It attracts its prey by using its golden silk along with the sun’s rays to create a shiny and alluring effect which attracts the spiders’ victims to their doom.
Another example of this can be the funnel web spider of the family Agelnedia. These spiders often build their webs in flat places close to the ground with dense webs which curl in a funnel towards the ends.
Their highly sensitive threads help them detect even the slightest movement and differentiate between prey and predator. 

Funnel-web spiders wait patiently for their prey to stumble into their den and strike quick and grabs their prey before it has any time to react.
Hunting spiders are those arachnids which prefer to hunt prey actively and use tactics like ambush. They do not rely on their webs for hunting.

Wolf spiders of the family Lycosidae actively hunt for prey on the ground. They are found under rocks and pieces of wood and are commonly found both indoors and outdoors. They lay their eggs in an
egg sacs made from their webs.
Jumping spiders of the family Salticidae are very common. They are often seen hopping small distances but can jump large distances too.
They have excellent eyesight compared to all the spider species. They actively hunt their prey. A good example of a jumping spider is Portia fimbriata also known as the fringed jumping spider, it is araneophagic (feeds on other spiders) and is highly intelligent and learns and modifies its hunting strategies based on its prior encounters.

Biological control is a method which involves the use of natural predators to deal with the pests that pose threats to the crops grown by farmers. It is a component of integrated pest management. It is a practice that puts a heavy emphasis on the use of natural predators found in the surrounding environment to counter the abundant prey population that ruins the farmers' crops. The potential that lies in this practice is immense and untapped and serves as a valuable alternative to the use of chemical
fertilizers and pesticides. This practice has slowly gained momentum over the years and is being carried out by farmers throughout the globe. Spiders are a species of organism that is present in abundance on this planet. They are ubiquitous and often inhabit dark places in their environment. The involvement of spiders in biological control remains relatively unexplored but harbours immense potential as an efficient predator that aids in insect and pest suppression.

Spiders are now seen as a potential asset in the field of biocontrol and integrated pest management. They can be seen in coexistence with rice crops, apple orchards, cotton fields, greenhouses and even
vineyards. When it comes to rice crops, an investigation and survey were carried out in the cultivated fields of the Swamimalai Region of Cauvery Delta, Tamil Nadu. The researchers found a total of 31 species under 13 genera and 13 families. All the species were found near buildings, wooded areas and cultivated fields. Family Salticidae was the most represented family in this region with other families like Lycosidae following close behind. It was observed that the distribution of these families was found to be continuous and discontinuous. Their colouration was often impacted by the different environmental effects of the environment and due to the difference in their behavioural pattern. It was found that spiders like Ctenus sp. (wandering spiders) and Draposa sp (wolf spiders) were natural predators of rice pests and that removal of pesticides urges the spiders to build their nests in the rice fields further increasing the field's productivity and ensuring pest population control. A study conducted at Cajamar Experimental Station in the province of Almeria, Spain carried out the assessment of specific relationships between spider guilds, pests and natural enemies. The aim of this study was to select plants which help boost biocontrol services by spiders outside the greenhouse for the reduction in pest populations and their decolonization in greenhouses. The study area used contained a diverse range of plants from herbs to shrubs and nectar-rich, pollen-rich and nectar and pollen-rich plants. The greenhouses had different vegetable production consisting of tomatoes, peppers, and cucumbers. The arthropods used in the study were collected from 161 plants and the spiders were further sorted into a
functional group of web-weavers and hunter spiders. The results of this study showed that some spider species were abundant in certain native plants. Temperature too had an impact as stated that hunter spiders were abundant at 35.8 °C. In contrast, web-weavers were abundant at 27.4 °C. A. cytisoides and T. vulgaris, supported a larger number of hunters, while web-weavers were more abundant in E. fragilis, O. europaea and R. sphaerocarpa. As stated above the increase in spider population was linked with the weather conditions, hunter spiders growing in abundance from late spring and summer. Some plants such as G. umbellata, R. officinalis, and others were selected by spiders and supported levels of pests suggesting that there is a co-occurrence between natural enemies and pests and thus indicating a probability of biocontrol. It was also seen that low and sparse plants supported a lower spider population. An exception to this would be the plant C. maritimum which supports a high density of
spiders, mostly hunters. Benefiting spiders means that the spiders will predate more on whiteflies and thrips which are often vectors, reducing the transmission of a virus into crops by pests. They will also help to keep the population of these pests in check reducing their chances to colonize in the greenhouse.
All in all this study shows the positive relationship between spiders and pest abundance in some plants, indicating their potential for biocontrol.

Similarly, other studies carried out in study areas of vineyards and apple orchards suggest the same theories and highlight the facts regarding the relationships between prey abundance and
spiders in specific plants present in the environment.

Spiders and their generalist approach to feeding opens up new ways and methods for their implementation in biocontrol. We should understand their importance and the prerequisite conditions required for their growth in order to fully bring out their potential as agents of Biocontrol and pest management. Heavy stress should be laid on the usage of pesticides in agricultural fields as it harms many organisms including our favourite arachnids and prevents them from approaching our fields as a potential nesting area. Their presence in the fields is immense as they regulate prey populations and prevent their colonization. This in turn leads to healthy crop harvest and a healthy produce turnout as
they also feed on insects which carry viruses which can spread rapidly through food consumption. Spiders are highly misunderstood creatures and are feared due to their appearance but play immensely important roles in the ecosystem. The potential of their implementation in Biocontrol
methods is vast and something to look forward to in the coming times.

~ Achyuth Sundar

Citations: 
https://www.dzarc.com/entomology/article/view/237/225
https://www.sciencedirect.com/science/article/abs/pii/S1476945X07001080
 https://sci-hub.se/https://doi.org/10.1146/annurev.en.29.010184.001503
 https://www.mdpi.com/2075-4450/9/1/33