Relaxing Lepidoptera

Here is my method for relaxing lepidoptera.  Just like everything else, it seems like everyone has their own system and procedure.  Mine might not be best for every situation, but it is designed for pinned specimens in bulk.  I get through a few thousand leps a year, but it can be easily scaled to meet your needs.

  1. I use one of these medium-large snap-top Tupperware containers that you can find in any market.  The dimensions are roughly 8″x5.5″x7″.  Any well-sealing container can be used.
  2. Grinter Relaxing ChamberI create a rough wooden frame to place in the bottom of the container (I supposed making it out of bent metal or something would be preferable).  This keeps the bottom pinning surface out of the water, which means it’s very easy to lift out.  Placing the foam directly onto water causes a slight adhesion that makes removal difficult, especially without dripping or splashing.  Within the frame I stuff paper towels for absorbance.
  3. Relaxer InteriorAdd enough tap water to moisten the towels but be careful not to allow for standing water.  This is just a precaution to avoid splashing, especially if the container is bumped or knocked over.  I avoid using hot water because the excess steam creates too much condensation that can drip onto the specimens.  My theory is the slower the better, no reason to rush good specimens!  But if I am ever in a rush I will add warm water or gently heat the relaxer making sure to leave the top layer empty as a drip-guard.  When using hot water be sure to insulate the top of your container to help resist condensation.  But, heat can create excess greasing in some species, so this should be avoided unless absolutely necessary!
  4. I cut foam pinning trays to fit.  Using #7 pins (stainless would be best) I create a perimeter on top of which multiple layers of trays can be placed within one container; the middle two pins are placed as a pull.  The bottom layer can not accommodate large specimens with wings folded dorsally, but they can either fit in the top layer or when only one layer is being utilized. Relaxing Parts
  5. I then load specimens and place into the relaxer.  For papered specimens I simply place them flat onto the foam, but it is inefficient space-wise.  It usually takes 6-8 hours for microleps to be relaxed, 1 day for small or delicate leps like slender Noctuids or Geometridae and 2-3 days for the majority of Noctuidae and even Saturniidae.  Sphingidae seem to usually take 4-5 days, and stubborn ones I inject with a small amount of water to facilitate relaxing.  I can typically spread the contents of one relaxer in 4-5 hours (sometimes spread over 2 nights) and since I only have 20 spreading boards I never have had the need for constructing a second relaxing chamber.
  6. I do NOT add any chemical mold repellant such as chlorocresol, naphthalene or PDB.  I used PDB for a few years but the vapors are extreme, especially when working at your desk for hours.  Instead I carefully wash all surfaces with 95% Ethanol for sterilization after each use (boiling water might be substituted).  You can keep the paper towels for weeks or even months if you carefully soak in ethanol and rinse each time.  I allow for only a minute ethanol residue because excess alcohol inhibits proper relaxing and you end up with crispy wing-joints, even after a week.  While this method prevents mold for 5-6 days it is not fool-proof.  I have forgotten about specimens and within 7-8 days some light mold will begin.  Despite this, I find this method creates the most satisfactorily relaxed specimens out of anything I’ve tried.

The results!

7 comments to Relaxing Lepidoptera

  • Im definitely going to have to try this, the only method I ever learned for leps was dipping the thorax in boiling water. I never liked the idea and always had mixed results. Have you tried relaxing other insect groups this way?

    Btw, I like the set up and concept of you website and enjoying learning about what Lep freaks do :)

  • Yes this would work just fine for any group of insects, I’ve relaxed Hymenoptera this way with great results. Some of those really large beetles though take an extra effort, and I’m no help there!

    I can imagine the dipping method is rough, I try to avoid any contact with water.

    Here is an alternative relaxing method which you could use for quick relaxing: It gets the job done quickly but also gets things pretty damp.


  • Leif


    Have you relaxed mikro lepidoptera ???
    I meen the small one.
    And how can you control at butterfly do not get wet ??

    • For very tiny moths I do not relax – things like Nepticulidae have to be spread while partially alive or very, very freshly killed. Most tiny species need to be mounted this way if at all. When I find them in a light trap I just pin them without spreading. But when they are on a sheet I capture in small vials for prep under a microscope the next day.

      Keeping the water at room temperature keeps the condensation minimal. I never have had drops forming on specimens.

  • Toby Finke

    what do i do if i relaxed a bug like 3 times like 3 days each and it is still not flexible. it is a stag beetle and the legs move, not the mandibles

    • Beetles are a special case and often require a totally different method for relaxing. Quickly submerging a specimen in warm or simmering water can do the trick – gentile relaxing at room temperature is really only for delicate specimens like Lepidoptera. You might want to search around on beetle blogger sites for better advice on relaxing big, stiff, beetles. Good luck!

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