Dear Sebastià,

I can only give a partial answer as I've never used DPX. I'd also like to hear from people who have. Whenever you experiment with a new media, it's worth making some slides in both something "traditional" and the new media so you can make comparisons. I've experimented a bit with DMHF, for example: it's good and seems to last, but suffers from not further clarifying the specimens after they're mounted. When you mount in Hoyers or PVA, you'll notice that the specimens don't look great at first, but after a few days in an oven they're beautifully cleared. So I could only recommend DMHF for big mites that you don't need to see the fine structure of, or "back-up" mounts.

How easily specimens can be remounted is also important. Can you recover specimens if the mountant spoils? That's very easy with Hoyers as it soaks off in water and I have made many good remounts (and just a couple bad ones, so there is risk...)

It's always worth bringing up the following link:

https://www.nhm.ac.uk/hosted_sites/acarology/archive/summary.html

I still use Hoyers, but PVA is also popular. Make sure that you ring your slides (with an insulating varnish/paint) and store them in a dry environment. If you have time, use another mountant (like Canada Balsam) for a subset of specimens. What you sacrifice on optics and simplicity of mounting you may well gain with permanency. If you find yourself working in the tropics with no climate control, then it becomes more important, even essential, to avoid these hygroscopic media like Hoyers.

Kind regards,

Owen.

Dear Sebastia,

I use Hoyer as well and, at least during the time I observed the samples, I do not have spotted long time changes.

I would use DPX rather for sections than total mounts, as it losses quite some volume. Do you want to imbed aquatic mites, fresh ones, or ones stored in ethanol? In case terrestrial mites, which were not stored in Ethanol, DPX would be an option (air dried, not in an oven). Otherwise I would recommend Hoyer, if the samples can be stored safely. If not exposed to high humidity Hoyer should be as long-term applicable as DPX. PVA might be an option as well, as mentioned above.

Best regards

Thies

Dear Owen and Thies,

Thank you very much for your time and advice. I will use Hoyer’s medium as you recommend as I should not have humidity problems. I would like to study terrestrial mites, specially those associated with insects.

I really appreciate your comments,

Kind regards,

Sebastià

It seems that Hoyer's may be good for

acari because of its self-clearing properties. However, it is not acceptable to mount Mallophaga or Siphonaptera in Hoyer's. Traditional clearing, dehydrating, and mounting in Canada Balsam is the only way to go. I have used such archived slides that were over a century old, and remain in good shape.

Dear William,

Thank you very much for the information, I didn't know that, so I will definitely take it into consideration.

Best regards,

Sebastià

Dear Sebastià and Thies, I had some trouble with Hoyer´s medium containing lactic acid (2:1 Hoyer´s:lactic acid), within a few days, long crystals formed, beginning at the edges of the cover slips, and finally rendered my preparations (Diptera larvae) useless. So, from my experience, I wouldn´t recommend to only use Hoyer, if the slides should be stored for longer period of time. I am not aware of any high levels of humidity, the slides were stored at RT. Has anyone an idea why my self-made Hoyer´s behaves that way?

Dear Christoph,

in my experience, no lactic acid is needed in Hoyer for mites. I never used lactic acid and I just checked my oldest own samples, because of your observation: though more than ten years old, they are fine. Excess lactic acid can crystallise, therefore I suspect the crystals are crystallised lactic acid. Did you seal the sample?

Bests

Thies

Hi Thies, in fact I didn´t seal the preparations, because I thought it will be fine to let the specimens clear for a day and then take the pictures (of course it took three days or so until I took the pictures). So it worked for me, and the specimens were perfectly clear.But mentioned crystals were annoying. I´ll try next time without lactic acid, just added it because I read it will enhance clearing. Which sealing do you recommend?