Why Farmers Actually Like Spiders
On a single plot of rice paddy, at least six different types of spiders can be found living side by side, from wolf spiders and long-jawed spiders to lynx spiders and tiny species numbering in the dozens per plot. They are not pests or a threat. They are all predators that hunt planthoppers and other small insects that damage rice plants daily. While many people shudder at the sight of spiders, farmers who understand the paddy ecosystem welcome their presence.
It is important to note that spiders are not insects. Taxonomically, they belong to the Arachnida class and have eight legs, unlike insects which have six. However, in terms of their benefit to farmers, spiders are on par with the best natural enemies from the insect world. Several types of spiders are commonly found in Indonesian rice paddies, each with a different hunting strategy.
The wolf spider (Lycosa pseudoannulata) is an active hunter that directly seeks and chases its prey. Its effectiveness depends on the size and activity level of the target; it tends to be more effective at catching less agile prey, such as green planthopper nymphs that cannot yet fly far. The lynx spider (Oxyopes javanus) has a distinctive appearance with hexagonal eyes and long, spiny legs, measuring about 7 to 10 millimetres. It is highly productive, capable of preying on eight white-backed planthoppers a day. With a lifespan of around 150 days, a single female can produce up to 350 eggs in her lifetime, meaning the predator population can regenerate rapidly as long as its habitat is maintained.
Unlike the previous two types, the long-jawed spider (Tetragnatha spp.) employs a more passive hunting strategy. It tends to remain still during the day, but at night it actively builds webs. Prey trapped in the web is then captured and eaten. This type of spider has been recorded preying on various planthoppers, including brown, green, and white-backed planthoppers. In several paddy field studies, Tetragnatha was recorded as the most dominant spider species, especially in fields with high brown planthopper populations, as these insects are a primary food source.
One of the most fundamental ecological principles is that predator abundance is directly proportional to prey abundance. The higher the planthopper population in a field, the higher the spider population, because food is plentiful. This makes the presence of spiders an indicator that experienced farmers can read. A paddy field full of spiders is not a problematic field; on the contrary, it is a field where the natural defence system is actively responding to the presence of pests.
Unfortunately, spiders are highly vulnerable to broad-spectrum insecticides. Studies comparing fields using Integrated Pest Management with those using conventional practices consistently find much lower spider populations in fields frequently sprayed with chemical pesticides. When spiders are wiped out along with the target pests, the paddy’s natural defence system collapses. Unlike natural enemies that need to be specially cultivated in laboratories, spiders will come and breed on their own as long as their habitat is not disturbed by unnecessary pesticides. Farmers do not need to do anything special to obtain the services of spiders; simply letting them live allows them to work without being asked. The next time you see a spider web among the rice clumps, instead of feeling disgusted or disturbed, perhaps it is time to see it for what it really is: a free safety net working to protect the harvest.