The system in the lab is comprised of an uppermost salt water reservoir which is fed continuous fresh air to the bottom through the screw cap opening via an aquarium pump. A tube at the base feeds tubed water out to a filter and from there passes through a saline drip reduction ‘tap’ of the type used in hospitals. (courtesy Ross Thompson of the Sumner Longboarders Club)
These hospital drips are very reliable & though any small tap may be used, its efficiency is determined solely by the dependability of the filter itself. Of course keeping any foreign matter out of the top reservoir when refilling it, is as important.
The salt water then drips onto and through the sand container with the insect within (which has a piece of paper towel beneath) and then through the plastic pudding plate which has perforations in the base.
This must all be raised to a certain degree so that the maximum amount of salt water in the base trays does not flood them, otherwise an insect may pop up, crawl out and end up in salt water.
By the time the insect eventually surfaces I should think that it has had quite enough of salt water immersion.( I guess this sounds a little complicated so I’d better go & draw the arrangement) Several saline drip taps may be inserted along the outlet hose of the top reservoir if you wish, for several insects at a time.
These trays are interconnected by a plastic pipe (secured in place using silicone sealer inside and out) running through the bottom of all base trays, with several largish holes drilled in each section which passes through a plastic tray, effectively allowing all trays to fill to the same (low as possible) level. There is a water outlet at the base of only one overflow tray which flows into the bottom reservoir but you could double up as a precaution. This bottom reservoir must be capable of accepting all of the top reservoir’s water or there will be a ‘bit’ of a problem if the system is left (for some aberrant reason) unattended.
Of course the bottom reservoir must be regularly emptied back into the top reservoir for this contraption to keep functioning. You may decide perhaps to devise a method of automatically transporting the bottom reservoir’s contents back up to the top with an automatic pump.
Lab all set up for one insect on the saline drip.The tray with the outlet to the bottom reservoir has a view of the interior, albeit a little unclear.