3 Creepy Insects to watch out for during Japan’s Rainy Season!

  • Japan’s rainy season has begun, starting early to mid-June and lasting roughly a month. It’s time to start sweating from the heat and humidity, but also a time to appreciate the unique sights that emerge during this time like the beautiful hydrangea flowers that blossom in this season.

    If you choose to hide inside, you may not be alone as the warmer weather will likely draw out various insects as the rain drives them to find shelter. Here are just a few of the critters you may find lurking in your house. Practice caution and observation and these warm-weather insects won’t make your summer a bummer.

    Mukade, or Chinese Red-Headed Centipede

    This is a bug I personally can’t stand. If you go to the mountains or countryside of Japan, they are a common sight and are likely to be found in a warm cozy corner to hide in. In a Japanese home they might like to be under furniture objects like a bed or wardrobe. They can grow to around 20 cm and have a color scheme that makes them easy to spot: Red heads, black bodies, and sickly yellow legs that let them dart around pretty fast. The Chinese Red-Headed Centipede can have a pretty nasty bite, which have been likened to an electric shock. If you get bitten by one, it’s recommended to seek medical attention. You should run a fresh bite under warm water to open up the pores; if you wash the bite with cold water, that can actually cause the pores to contract and shut the poison in.

    These creatures are pretty nasty, so killing them may put you at risk of being bitten. Cutting them in half works, but the front end may continue to run and attack for a little while after. If you try to simply crush them, their body can release a pheromone which can attract other centipedes. If possible though you should try to avoid disturbing them, since they can take care of various pest insects while inside your house.

    The mukade were used by some samurai as a symbol of victory in battle. The Red-Headed Centipede makes use of its poisonous bite and legs to attack prey of various sizes, including small mice and snakes. Considering how aggressive they are, it is no wonder that they’re viewed as symbols of battle as they attack prey that’s larger and deadlier. These centipedes are seen as one of the apex insect predators.

    Wolf Spiders

    These predatory spiders are brown in color and can be found in flat, dry areas. On sunny days it can be easy to spot one wandering around outside. I have occasionally seen these just inland of the beach where I work, and on rainy days a few have been spotted running along the hallways and hiding in cupboards. Instead of spinning webs, wolf spiders live in burrows and hunt their prey by jumping and tearing into smaller insects that wander past their burrows. They can grow to up to 10 cm, so they aren’t a big threat to humans. They are often solitary, so if you see one you don’t have to worry about an infestation. That being said, there is a particularly nasty feature of these seemingly boring-looking spiders.

    If you find a wolf spider, check to make sure it isn’t a pregnant mother before you decide to do away with it. Mother wolf spiders carry their eggs and young baby spiders on their backs for at least the first week of the babies life. This can be up to 200 spiders. So if you see a wolf spider, try not to just whack it in hopes you will squish it, because you may rid yourself of the mother just to end up with 200 tiny babies scattering in every direction.


    These little buggers are everywhere, and if you think the rain will keep them down, think again. There may be fewer of them in the rain, but that doesn’t mean these minuscule little monsters won’t follow you throughout your house and feast on your blood whilst you sleep. Thankfully, mosquito repellent is easily available in Japan – your local convenience store should stock you up with repellent for your skin. If you need something a little more heavy-duty, you can get incense coils which drive them away, and sticky traps to hang around. I always find that no matter the weather and what deterrents you use, mosquitoes always find a way to get inside. They are active all summer but the start of the rainy season is a reminder to start defending against yourself against bites and potentially contracting an illness. Even in Japan mosquitoes retain their reputation as one of the most annoying and persistent insects around.

    As with all bugs, there are preventative measures to take but nothing can assure that you will be able to avoid finding one of these critters, and any number of other bugs, in your house, hotel, or whilst you are out and about hiking or even shopping. These are just a few of the insects that are pretty common during the rainy season, but there are many, many insects in Japan. If you plan to be active outside or staying in a warm house during the Japanese summer, stock up on bite cream and stay vigilant.

    Bonus: Fireflies (Hotaru)

    The start of the rainy season is a good time to look for fireflies, called “hotaru” in Japanese. Many locations do official showings, where they release clusters of them into a park or hotel grounds so visitors get a chance to see them swarming like little glowing stars. If a set-up tourist attraction isn’t your cup of tea and you would rather see them out in the wild, after a rainy day is the best time. You can sometimes find wild ones along quiet river banks or standing ponds in rural areas just after sunset.

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