Please be careful of the venomous "Black Widow Spider" and "Brown Recluse Spider"

Poisonous black widow spiders and gray house spiders, along with their egg sacs, have been found within the city.
The Brown Widow Spider and the Gray Widow Spider are designated as specific invasive species, and they have been confirmed throughout Japan, suggesting that they have established themselves in the country.
If you find a similar spider in your garden at home, please do not panic and handle it appropriately by referring to the extermination methods shown next.
Both types of spiders are timid and docile, with no aggression, but they are highly venomous, so please be careful not to catch or touch them with bare hands if you find them.
If you do not provoke them, you will not be bitten, but if you are bitten, wash the bitten area with water and seek medical attention as soon as possible.

Control Methods

In addition to using commercially available pyrethroid insecticides, you can also eliminate them using physical methods such as pouring hot water or crushing them with your shoes (since the eggs are not affected by the chemicals, please place them in a bag, crush them, and then use the insecticide).
If you step on an egg sac with your shoes, make sure to wash the soles of your shoes thoroughly to prevent any remaining egg sacs from hatching spiders.
Also, if one is found, there may be others lurking nearby, so please be careful and check thoroughly.

Symptoms When Bitten

It is said that a pain like being stabbed with a needle is felt, and the pain spreads beyond the area that was bitten.
Symptoms such as muscle pain and headaches may persist for several weeks.
There have been reports of severe cases such as muscle paralysis, so caution is necessary.

Response in Case of a Bite

In case of a spider bite, please promptly visit a medical institution.
Treatment with antitoxin serum is necessary in case of severe illness.
If possible, please bring the killed spider to the hospital so that we can identify the type of spider that bit you.

Characteristics of the Black Widow Spider

• The body length of females is about 7 to 10mm, and the body length of males is about 4 to 5mm (body length refers to the length from the tip of the head to the tip of the abdomen, excluding the length of the legs).
• Only the females are highly toxic and harmful; the males are not toxic.
• The entire body is a glossy black color, with a prominent red vertical stripe on the back of the large spherical abdomen.
• There is a red hourglass-shaped pattern on the abdomen.
• Inhabits places with good sunlight and warm spots, such as shadows and gaps.

Characteristics of the Gray Spider

• The body length of females is about 7 to 10mm, and the body length of males is about 3 to 4mm (body length refers to the length from the tip of the head to the tip of the abdomen, excluding the length of the legs).
• Only the females are highly toxic and harmful; the males are not toxic.
• The colors are varied, with a round body in gray or brown, and spots with a border scattered on the dorsal side of the abdomen.
• There is a red hourglass-shaped pattern on the abdomen.
• Inhabits places with good sunlight and warm spots, such as shadows and gaps.

To avoid being bitten by spiders

The Brown Widow Spider and the Gray Widow Spider can be found in urban areas in small gaps such as the grates of roadside ditches, the joints of wire fences, under vending machines, and in trash cans. They may also attach themselves to umbrellas, clothing, toys, and other items left outdoors, potentially being brought indoors.
During the extreme cold period, these spiders can endure the cold in small spaces with insulating properties, and during the high-temperature period, they can spend time in small spaces with higher insulation. To create an environment that is less hospitable for spiders, regularly clean areas where they are likely to inhabit.
Only the females are venomous, and if bitten, one may feel a sharp pain similar to being stung by a needle. In severe cases, the pain may spread throughout the body and could be accompanied by nausea and headaches.
You can use commercially available household insecticides to spray and kill insects. Additionally, when working outdoors, such as cleaning or maintaining flower beds, you can protect yourself by wearing rubber gloves.

• Ministry of the Environment Natural Environment Bureau Website "Invasive Species Act"(External Link)
• Ministry of the Environment created flyer "Beware of the Brown Widow Spider and the Gray Widow Spider!" (PDF 389.1KB)