When we think of insects that live in the tropics, we often get the impression that they are larger than the types that live in Japan. In fact, species such as the Formosan giant tortoise that live in Thailand are at least one size larger than the species found in Japan. This is also the case with the Indochinese giant cicada, which I introduced in this column previously. However, only some insects have grown in size; in reality, many insects are of the same size. Some insects are smaller than those from Japan.
A representative example of this is the carp beetle introduced here. The carp beetle, which inhabits not only Thailand but also a wide range of Southeast Asia, is about half the size of the Japanese carp beetle. Since we have not investigated it in detail, it is unclear whether these are all the same species or multiple types. When you're collecting fish, you'll notice them because they'll end up in your nets even if you don't like them.

I have heard that the type from Thailand that I will be introducing here is very similar in size and shape to the Formosan caterpillar that lives only in Okinawa in Japan, but this has not been definitively identified either. The Japanese formosan beetle is said to be extremely rare, as its population has decreased in recent years. Considering that the Thai carp beetle commonly inhabits fairly polluted waters, it may be that they are different species just because they look similar. The Thai carp beetle is commonly found in areas such as wetlands where aquatic plants, water hyacinth, and water spinach grow thick. It can also be found near brackish waters that are slightly salty. They are found in large numbers everywhere, and if you want to collect them, you can collect them in large numbers. Even when collected from the same location, there are slight differences in color between individuals. Slightly greenish and brownish individuals can be seen. It is unknown whether this coloration is due to aging. Individuals with greenish body color and red eyes are small but impressive.

Speaking of carp beetles, their characteristic feature is that the male carries the eggs he lays on his back. For this reason, it is also the origin of the name ``child-bearing insect''. Of course, the type from Thailand has the same breeding ecology. If you keep both males and females together in captivity, they will breed easily, so if you have a chance, I highly recommend you observe this interesting ecology.

In the past, my partner Tong from fieldwork in Thailand sold aquatic insects, including this caterpillar, to Japan. The Formosan giant tortoise and the Indochinese giant tortoise, which are larger and more impressive than those from Japan, are quite popular, but this one from Thailand was not popular at all and remained unsold. It seems that the general public expects foreign insects to have large, impressive appearances, and unusual shapes. It can't be helped that people don't find the product appealing if it's similar in shape to the Japanese product but is even smaller.

However, this Thai caterpillar is extremely hardy and easy to raise. Because it is small, it is possible to raise and breed it even in a small plastic case. All you have to do to set it up is to float aquatic plants such as Japanese pine and anacaris to serve as footholds in a plastic case filled with water. Normally, it is difficult to obtain live food to raise aquatic insects, but it is very easy to raise them with frozen red beetles without having to feed them live food. Even if they are not moving, if you spray thawed red beetles in front of them with a dropper, the moment they touch your leg, they will hold you and suck up your body fluids. You can easily tell that the caterpillar has eaten because its abdomen turns red. If you put a large amount of thawed frozen red beetles in there, they will recognize it as food the moment you touch it with your legs, even if you don't move. Of course, any leftover food will worsen the water quality, so remove it immediately. A bare tank without sand on the bottom is suitable for this type of breeding. Since the breeding container is small and simple, water changes are very easy. One problem with raising them is their excrement. Apparently they don't want to be in the water where they live, so they throw their excrement out of the water. The same behavior is also seen in Japanese carp beetles and giant tortoises. Because of this, the area around the breeding container tends to get dirty with excrement, which has a unique smell, so be careful.

Aside from their small size and lack of presence, Thai carp beetles are very suitable as pets. You may not have many opportunities to do so, but if you are lucky enough to see one, please enjoy raising and breeding them.