Ecological importance

Spiders can be found almost anywhere in the world, even in your bedroom. From jumping spiders to tiny house dwellers and orb weavers, I am sure you could find at least one if you know where to look! If you do see them, don’t see them as pests. They are probably there acting as pest control. Ants, beetles, bees, wasps, caterpillars, butterflies, moths, other spiders, whatever flies into their web or lands in front of them. Spiders aren’t picky eaters and will eat about almost anything that it can, even their own dead mother.

Source: https://youtu.be/Lt20PC4uHLc

These traits, allows spiders to potentially serve as bioindicators. The health and behaviour of a spider can tell scientists a lot about the ambient environment. In one study, spiders of the tetragnathidae family were used to identify the effects of metals from a coal ash spill in the United States1. I think the term “you are what you eat” works well to explain how the spiders act as bioindicators here as these spiders live near water bodies and eat aquatic insects. Therefore, the metals from the environment is accumulated in the spider. In another study, the webs from the pholcidae family were used to identify the amount of heavy pollutants, from vehicle exhaust and factories, in the air in Lahore City, Pakistan2.

A long-jawed orb weaver, tetragnathidae, by Katja Schulz licensed under CC BY 2.0

A daddy long leg, Pholcus pholcidae, by Olei licensed under CC BY-SA 2.5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Spiders are excellent natural pest controllers too. Without them, insects would absolutely destroy our crops and leave us in famine3. It was observed that spiders are effective in dealing with pests in crops, and this scales with the number and variety of spiders4.

This makes me wonder… With the increasing number of rooftop gardens/ parks here in Singapore, would we see more spider species that are not usually associated with built up areas?

Some spiders are specialised eaters too. Like how I choose to eat ramen whenever possible, Evarcha culicivora is shown to have a preference in eating mosquitos5. (Given how Dengue cases are rising in Singapore, these little guys might be especially useful now.) Interestingly, this spider is dubbed the Vampire Spider as it chooses to feed on mosquitos that have fed on vertebrates6. Its Malaysian counterpart, Paracyrba wanlessi, prefers to feed on the larvae of mosquitos instead of the adults. You don’t have to worry about these spiders biting you and sucking your blood directly though. Their fangs are far too small to pierce skin and being as small as they are, less than a centimetre, they will probably flee at the sight of a giant.

Not a Evarcha culicivora because the pictures are all copyrighted but both are jumping spiders. Source: https://www.maxpixel.net/Spider-Arachnid-Eyes-Predator-Jumping-Spider-Web-1577857

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Reference:

  1. Otter RR, Hayden M, Mathews T, Fortner A, Bailey FC, Oak Ridge National Laboratory (ORNL). The use of tetragnathid spiders as bioindicators of metal exposure at a coal ASH spill site. Environmental Toxicology and Chemistry. 2013;32(9):2065-8
  2. Tahir HM, Aamir H, Nadeem J. Use of spider webs as indicators of air quality assessment of Lahore City. Water and Environment Journal. 2018;32(2):292-300
  3. https://www.amnh.org/explore/videos/research-and-collections/profile-norman-platnick
  4. Michalko R, Pekár S, Dul’a M, Entling MH. Global patterns in the biocontrol efficacy of spiders: A meta‐analysis. Global ecology and biogeography. 2019;28(9):1366-78
  5. Jackson RR, Cross FR. Mosquito-terminator spiders and the meaning of predatory specialization. Journal of Arachnology. 2015;43(2):123-42
  6. Nelson XJ, Jackson RR. The discerning predator: decision rules underlying prey classification by a mosquito-eating jumping spider. Journal of experimental biology. 2012;215(Pt 13):2255-61.
  7. Featured image by me

8 Comments

  1. leeweemeng05 Reply

    Hey Justin,

    This post really gives me an eye-opening experience with spiders. I believe this has changed my point of view about spiders everywhere, regardless of how small they can be. I didn’t know that their own wonder of works can be served as bioindicators. The part which you mentioned that the webs from the pholcidae family can serve as indicators for the amount of exhaust pollutants from vehicles, that really caught my attention!

    I’ll keep an eye on your blog for more posts.

    Cheers,
    Wee Meng

    • just2 Reply

      Thanks Wee Meng! I never knew the webs could work that way too till I was searching this up.

  2. lixuan Reply

    Hey Justin!
    Jumping spiders are really common in my home and last month, my brother caught one and tried to raise it but released it because of army commitments… I never knew that species of jumping spider ate mosquitoes, I was wondering if there was any species of jumping spiders in Singapore that’d help to curb the spread of dengue and what are your thoughts on introducing them into Singapore?
    Lixuan

    • just2 Reply

      Hi Li Xuan!
      It’s such a shame your brother couldn’t keep it, they make great pets!
      Most jumpers in Singapore are generalists that eat anything their size or slightly large but the Adanson’s House Jumper that is super common have been noted to have a habit of eating mosquitoes. Since this spider is also cosmopolitan, I think they would probably work the best.
      As for the introduction of spiders into Singapore is a tricky one. As we have learnt, ecosystems have a certain balance to them, introduce a new animal or plant, and that balance may not hold. There have been cases of invasive spider species around the world which shows that despite being generalists, they can still cause a lot of problems. I think it would be wise to leave them where they are.
      Although, I would love some Peacock spiders…

      • ENV3102 Reply

        Hi Justin,

        Lixuan’s question is EXCELLENT. And so is your reply ! This is an ongoing issue with demonstrating the provision of biocontrol of insect pests – you have to consider whether the predator in question eats enough of the pest to actually make a difference.

        jc

  3. Zhang Zuming Reply

    Hi Justin!

    I am an animal lover as well but I used to be interested in only vertebrates. The way you introduce us to certain types of spiders is very interesting and aroused my curiosity in them. Thus I looked for some more interesting facts on spiders and suprisingly, I found that some spiders can actually fly, bu using electric fields! I also looked through their history of evolution. Their perseverance really amazed me. We definitely need to protect them and hope to see more of your interesting posts in the future!

    Zuming

    • just2 Reply

      They are truly wonderful creatures. Nice to know that somebody is looking up for them too, Zu Ming!

  4. Joanna Coleman Reply

    Whoa. I didn’t know ballooning was about electrical fields ! Thanks Zuming for making me look that up !

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