Citizen water quality monitoring in Kanagawa’srivers is continuing for 2023 (; my posts for October 28, November 4, 11, 18, 2022). For FY 2022, Japanese Biological Monitoring Working Party (BMWP) score for Yadoriki Stream 寄沢 was 8.2, the highest among the check points studied by monitoring troops for Kanagawa Prefecture. We’re aiming for the best score again for 2023, and have done so far 2 field research in different spots of Yadoriki Stream. We’ll see how they’re turned out to be at the end of the fiscal year. These days, I’m getting used to study waterborne creatures under microscope. Baby stoneflies are cute. Er, yeah, they’re dead as samples in alcohol … Humas are this cruel. God, would you please forgive me doing such study of dead insects?
What we can achieve with aquatic larvae under microscope is to identify their family, not species. I first thought it would have been due to our skill-level for microscopic study. Nope. Not because of us. Mr. Iga, an environmental consultant working with the Kanagawa Prefecture said, “In general we cannot figure out species of aquatic insects. To determine the species, we need to check adult bugs, or to be exact, male genital organ of an insect by dissecting it under microscope.” Oh my … at least volunteers for biological water monitoring are not required to do that in Kanagawa Prefecture. Though, observing baby bugs in water regularly, I gradually become wanting to see the grownups. It turned out to be it’s not so difficult for us Kanagawa Forest Instructors to meet the imago. The standard way of finding adult insects in forest is light observation. That’s what we do at least once a year in Yadoriki Water Source Forest (; my post on September 13, 2019). Last month, we congregated in Yadoriki Forest at dusk and built an observation base made of a white bedding sheet and lights. We waited quietly in the forest with coffee and snacks. They came, as always.
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| A point of river with alga. That’s the place we would meet lots of aquatic babies. |
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| Preparing for building the observation base |
Of course, the bugs coming to our light were not only adults from waterborne larvae. Previous years, my attention went to larger mosses or beetles gathering around the light. But this year, I had a kind of new excitement anticipating the adults from our specimen larvae for microscopic study. My expectation was met beautifully. Yeah, unlike large insects, the adults of water nymphs were small. Come to think of it, as babies they require us to use microscopes for detailed observation. They then turn into chrysalis in a cocoon, and metamorphoses into adult. Or, for mayflies, they first become subimago, then metamorphoses to full imago. In the process, they normally do not double or triple their body size. Small nymphs become not-so-large adults. Even though, their delicate wings and expressive eyes were impressive.
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| A flashier visitor to our observation tool: Mimas christophi |
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| Superstar Actias selene and could you see lots of mayflies? |
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| A female stag beetle |
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| It’s a large mayfly (of their order). |
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| A Sweltsa abdominalis |
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| … Photos getting smaller. Another family of mayfly |
These adult bugs, being it stoneflies, caddisflies, mayflies, or crane flies, have very short lives. These creatures spend 1-3 years underwater as larvae. For the final 7 to 10 days of their lives they metamorphose into adults with wings to fly. The majority of adults even do not have mouth, i.e. do not eat at all. Most of them live their lives only to find mates and procreate for the next generation. I’ve heard these days biologists find LGBTQ+ is not rare in animal kingdom. Then, the lives of LGBTQ+ of such flies would sound even more romantic … I recalled a fortuneteller told me once my next reincarnation will be an insect. She consoled me “Well, even if it is so, it will be short and not much agony during your next life.” … Er … is that so? Or will I be an indicator-species underwater showing the water quality of somewhere on this planet or beyond?
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| Don’t you think it’s cool? Not all nymphs of mayflies have aquatic life. It’s Protidricerus japonicus whose baby lives on ground under fallen leaves. It also visited our light observation base that night. |
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/
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