Normally, when we’re walking in forests, it’s a day, not a night. Those bugs we encounter are not coming to us, except mosquitos or the like. In contrast, during night when we light a non-LED torch, nocturnal insects come to us. That’s something everybody knows, I guess. Now, let’s take such nature of bugs and have a party with them under torch light! That’s an idea of insect observation with night light. This summer, I had occasions to join such activity in Yadoriki Water Source Forest やどりき水源林. It was mesmerizing experience, I tell you. We installed a simple stage for insects to come guided by artificial light, and welcomed, literally, a wonderful cadre of bugs which usually are very difficult to meet. This week, I tell you my night adventure in Yadoriki with bugs!
First, the preparation. Under the guidance of senior forest instructors, we built a “stage” for bugs to come for human light. We pitched a white screen made of cotton linen in a somehow exposed space in Yadoriki Forest. “You see? We need to indicate insects from 360° that our light is here. We chose this place which is relatively open in a deep valley. When we light up the screen, it should be seen from all the directions including from the peaks and ridges.” We installed 5 lights illuminating the white linen. 2 of them were good ‘ol fluorescent white lamps. Another was 2 black lights that emitted ultra-violet light invisible for humans, but heart-throbbing for insects. We attached these 4 lights on the screen. We then flashed a large torch light towards the stage. The scenario was, the bugs in the forest would see something illuminated (by the torch light) in an open space. They came near to find more inviting vibe of florescent and black lights and stayed on the screen for us to observe them. When the sun set, we switched on the 5 lights for the white screen and waited in quiet and dusky Yadoriki Forest, eating supper. All things come to those who wait.
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| A florescent lamp and a black light |
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| A torch light |
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| We used these two wooden
benches. Four additional feet (; a foot is indicated by the yellow arrow here) of the same benches were |
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| Utilized to construct the frame for the screen, like this. |
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| The base for the screen is ready. |
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| Stretching the white linen securely … |
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| Installing the lights … |
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| In this version, we attached 2 black lights on the sides of the screen. It did not work well as we did in the above photo where we installed these on the top. We changed the place for the black lights to the top during the session. |
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| The rise of the curtain! |
It is said that insects active during night use moon light to navigate through pitch-black space. As moon is very far, when the bugs keep a certain position against the moon light, they can determine by themselves their flight course. Now, when humans bring artificial light, insects mistake our brightness as moon, and try to maintain their aeronautical angle to man-made illumination. Alas, human light is too near for them to hold one direction in this way. They spiral near and near to the light source and end up on the light itself. Observation of nycterine insects with lamplights uses such characteristics of bugs. How the stage of ours was looked like for them in the forest, I wondered … Night howls of deer were echoing in dark Yadoriki Forest. They were alarmed by strangely illuminated white something in their valley … And the insects came.
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| Welcome! |
First it was small mosquito like bugs. What were they? Mayflies, stoneflies … They were so many … and tiny. To identify the species, I’ve learned, we need to note the details of their body, like the way lines of their wings go, the construction of the segments of their abdomen, etc. We need really good magnifying glass, and an extremely still mayfly on the white linen that allows us to study their body construction. I quickly abandoned such analysis, and decided to admire their existence on a white screen. It was a fascinating scenery. They have only one day, or a couple more, in their life to have such apparition, after a long aquatic life as larva. Hmmm … our white screen might be a convenient dating café for them to find a mate in quick, as they were so many … Eventually, larger bugs started to come, like drone beetles, stoneflies, squash bugs, etc. Even Orobdella octonaria Oka visited us. It was a large leech. The one we met was about 30cm long. It swallows earthworms down, sacks its bodily fluid as meal, and spits out the dead worm. (Woooooooooooooooow.) Ours did not have any prey in its mouth, but it seems to me it liked to move towards the direction of light source. Earthworms are moving the opposite direction of light … then, why did this giant leech come to the light? I wondered.
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| A stonefly, Gibosia thoracica (Okamoto) |
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| A mayfly |
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| Prionus insularis |
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| Orobdella octonaria Oka. Though it looks grotesque, the creature itself is not interested in us humans. It will never attack us like vampire leeches. Relax! |
The time for those larger insects (and a leech) congregating around the light, it was for the protagonists and the primadonna to show up. The hero of the night was Miyama stag beetle. It is a stag beetle whose females lay eggs only with the temperature lower than 25°C, and hence dwells in cooler area of deep forests made of deciduous trees with lots of sweet sap. As Japan is observing warmer climate these days, it is becoming difficult for us to encounter the insect although they are active not only in night but also under day light. Japanese authorities think it is nearing to the endangered species status … They came to our white screen in deep Yadoriki Forest. We held our breath and admired their strong presence on the white linen. “Wow! Look! They are large. 6 or 7cm long?” “He surely gets angry. How aggressive his angry pose is ...” “And this one does not want to fight.” “Peacenik?” “Maybe.” These stags are strong enough to pierce our nails when we are so rude to this king of the forest. And so, I felt nervous to think such a strong looking beetle is approaching to rarity. I remember decades ago we could find them more easily during summer camps … Whatever is said about global warming, the ladies of Miyama stag beetle cannot bear babies when it is too hot. That’s for sure. And we cannot meet them easily these days. Is it just a coincidence?
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| A male Miyama stag beetle threatening anybody nearing him. |
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| Two stag beetles maneuver delicate balance of power … |
Primadonna of torchlight observation was moths. First smaller ones came, like Pseudoips prasinanus and Scopula superior, etc., etc. Then, bigger Madonnas appeared. Mimas christophi, Eudocima tyrannus, and magnificent Actias aliena … I tell you moths are dead gorgeous. I don’t know why people treasure butterflies more than moths. Ages ago, there was a hut called Komaba Little Theatre 駒場小劇場 in Komaba Campus of Tokyo University. One week before Christmas, a theatrical company called Yume no Yuminsha (“Dreaming Bohemian”) led by Hideki Noda 野田秀樹, performed there a drama “Forty-Seven Ronin: Mathematical Induction by Fabre who could not be an insect 赤穂浪士‐昆虫になれなかったファーブルの数学的帰納法.” The playwright-director-leading actor Noda played Fabre who was a nerdy and neglected kid. In a typical twist of Noda’s theatre, Fabre boy grew up to be a tyrant Actias aliena. (So, Fabre became an insect in the end, metaphorically or not.) In the play there was a conversation of characters which went like “How beautiful that bug is,” “But that’s a moth,” “What!? (With a disdaining tone) A moth!?” After Fabre metamorphosed into Actias aliena, the entire scene became really dream-like and Noda’s shining white costume was brightly illuminated by lights of a large mirror ball. I simply wondered why such a beautiful Actias aliena was treated in that way for the story. Komaba Little Theatre was really a crumbling old empty space filled with young energy of artists and audience. We directly sat on concrete floor in an evening of Tokyo’s December without heating. I had not seen real Actias aliena yet. Ever since, encountering living Actias aliena was one of the items in my bucket list. This summer I’ve checked this important item of my life.
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| I took
a photo of Eudocima tyrannus from this angle. Don’t you think it resembles to some Pokemon characters? Cute! |
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| Microblepsis manleyi |
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| Does Mimas
christophi look like a fighter jet, or a fighter jet look like a Mimas christophi? |
Actias aliena was really beautiful, and large. Although it resembles to weightless fairy in a photo of Wikipedia, in Yadoriki living Actias aliena flapped its wing with noise and struggled to find a hold strong enough to sustain its weight on a vertically stretched white linen. Yes, it looked as a magical creature, but they were desperate to find a mate during its very brief adult life without mouth to feed itself. I’m not sure if Hideki Noda knows living Actia aliena in fact. But I’m somehow convinced of Actias aliena for “Forty-Seven Ronin” in Komaba Little Theatre. Not everybody depreciates you, the moth. You’re magnificent, at least Naomi knows.
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| We
were visited by several Actia aliena on that night. Our observation screen might have been a dating spot for them … |
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| We
could not identify what it was. If you have any idea, we appreciate your kind help! |
Oh, by the way, night observation sessions of insects in Yadoriki Water Source Forest is a kind of privilege of Kanagawa Forest Instructors. The place prohibits the usage of fire or electricity without permission of the landlord, aka Prefectural Government. We do citizen science with annual night observation sessions to check which species are alive in Yadoriki Forest. The senior instructors are mulling a plan for such an event in Yadoriki Forest to visitors. One of them told me Kanagawa Prefecture is not positive for the idea as the place is in a deep mountain and night risk for casual guests are non-negligible. Please keep crossing your fingers … Someday you maybe able to join us. 😊
If you find an 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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