In Search for Lost Crickets: endangered Euscyrtus japonicus

 

Euscyrtus japonicus is in the family of Gryllidae, aka crickets. It’s tiny. It has 1-1.2cm of body length. Its legs are very slender. Their wings are not sturdy enough to fly around. So, they are not good at moving. It doesn't sing, although it’s a cricket. Probably the most prominent feature of the bug is female ovipositor, the organ to lay eggs, which has almost the same length as its body. Otherwise, it’s low-key. Having said that, it’s picky for its meal. Its diet comes only from long leaves of grass families. They are not good at exploring new worlds for food with their weak wings and legs. When they have home, they make a large colony in the same bush of grass with their fellow crickets.

People from Yokohama Environmental Science Research Institute, a watch dog in charge of environmental pollution in the city, have found the bug VERY rare in the city. For that matter, in the entire Kanagawa Prefecture, meeting them is getting rarer and rarer. In the recent Red List for insects and spiders in Kanagawa (my post on September 6, 2026), they are categorized as VU = vulnerable. It’s same in Tokyo, Saitama, and Chiba. All of these prefectures including Kanagawa give Euscyrtus Japonicus the endangered status. There were lots of bitten leaves, for sure. But. Some had bite marks at its tip. The others were eaten from its edge. Unfortunately, no leaves with holes only in the middle.

Instead of crickets,
brown winged planthopper
(Pochazia shantungensis)
 is ubiquitous these days
in grass of Yokohama …
They are registered
“invasive species
that harm orchards”
 by the Plant Protection Section of
Ministry of Agriculture,
Forestry and Fisheries of Japan.

Er, well, it sounds demanding but at least around Yokohama, it seems to me grasses are abundant so the insect may not have hard times for survival. I decided to do a mini search for them in the wide expanse of grass family along the bank of Tsurumi River. The bugs leave very characteristic feeding signs if they are there. They eat only the middle of slender leaves of grass. They avoid apex, margin, and of course midvein. After their meal, the grass leaves have lots of elongated holes in both sides of midvein. Since they live en masse, the leaves of their grass “town” are supposed to have lots of holes. It must be easy to find them ... Result? Nah.

It seems to me
there are lots of meal here for the crickets.

This young Patanga japonica
has surely different table manners
 from Euscyrtus japonicus.

I simply wondered. Why? With such a lot of leaves, the cricket must be able to eat a lot. One speculation could be their be-loved field of grass which can undergo frequent disturbances in big cities of boiling planet. Take the bank of Tsurumi River. Thanks to this changing climate, sudden torrential rain over our concreted neighborhood pours water directly into the River. The grass on the bank will be inundated at once. Even if the flood is for a very short period of time, it’s enough for tiny crickets to be washed over, and extinct. Or flood control constructions. The bank receives heavy mowing at least once a year to stop overflowing into human area. Yeah, grass will come back soon but meanwhile what to eat for these picky crickets?

It’s a hard life for this inconspicuous insect. What will happen to them? I decided to search for holes when there is abundant grass in our neighborhood. The scenery looked familiar and permanent. But from Euscyrtus japonicus’ point of view, it’s turbulent surroundings. I recalled the quiet fury of these bugs’ nerds in the symposium. “Beautifully conserved nature? Look, who’s talking!?”

If you find environmental issues in Kanagawa Prefecture, please make a contact with

Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター
657 Nanasawa, Atsugi City, 243-0121
〒243－0121　厚木市七沢657

Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/