We use standardized funnel-pitfall traps for years with 2% formol. Evaluation against cup traps showed better catching of the funnels.

http://www.wsl.ch/land/biodiversity/zoology/publications/traptypes/pu_traptypes.html

We dig in a 30 cm piece of standard sewage pipe (15 cm diameter) in the ground. We then insert a wide-neck 750 milliliter plastic bottle with a funnel screwed to the neck (neck diameter 3 cm). The funnel rim sits flush on top of the sewage pipe, the bottle therefore hangs on the funnel. The bottle is filled to 3/4 with 2% formalin-water and a drop of detergent. Small holes . . . . drilled just below the neck prevent filling of the trap with rain water. We use a transparent plastic roof xxxxxxxxxxxxxxxxxxxxxx to avoid water and debris in the funnels. Finally a wide wire cross cccccc (diameter 1.5 cm) prevents small animals from drowning. If anybody is interested, send me the postal address and you'll receive a reprint of: Obrist, M.K., Duelli, P. (1996) Trapping efficiency of funnel- and cup-traps for epigeal arthropods. Mitteilungen der Schweizerischen Entomologischen Gesellschaft. 69:367-369Cheerz Martinmartin.obrist@wsl.ch

>Formalin may work in your neck of the woods, but here in the Mojave>Desert it evaporates rather too quickly (in less than a week).>Propylene glycol (preferable to Ethylene glycol because it's>essentially non-toxic to vertebrates) takes months to evaporate. This>is important in the case of traps set to sample remote areas and left>to be picked up several months later. And in the case of pan traps,>the usual depth of formalin solution can evaporate in the course of a>day in summer.Are you using straight gylcol? It is hard to imagine anything lasting 3months in the Mojave desert! Propylene glycol maybe less toxic to mammals,but in my experience it still attracts them. As I mentioned, if one decidesto go with glycol, adding a little formalin will certainly make it tastevery bad. Also, I have always thought invertebrates "perserved" in justglycol were "mushy".I too have frequently left traps out for many weeks, even months, but I havetrapped mostly in temperate forests of Pacific Northwest. The evaporativepotential of pan traps vs. pitfalls is significant becasue of the differencein surface area:total fluid volume. Depending upon climate and exposure, thecomposition of trap fluids may be adjusted to meet needs. At least in myarea, pitfall trap in most habitats need only very dilute formalin. In coolmountane habitats traps can be left out easily for two months, otherwise onemonth is better. Of course, the larger the interval the less information onphenology.Foramlin will not necessarily completely solve the mammal problem, but ingeneral they will not destroy the entire trapline, as I have seen them dowith glycol. Black bears can be especially troublesome.
I have also experimented with vinegar. In fact I did this last summer innortheast Washington at ca. 3,000 ft. in dense cedar-Larix-Pinus forest,with good results. What I did was mix one pint of methanol with one gallonof vinegar, and a little dish soap. This avoided the poison problem offormalin, which made the whole process more enjoyable. I left them out for>1 month, which was pushing the preservation potential of the mixture. (Ihave yet to find anything that preserves as well as even very diluteformalin.) One other advantage of formalin that I haven't mentioned - if youare working in very remote locations with access to water, all you have todo is pack in full strength formalin and then dilute ~5 formalin to 95 partswater, which is quite an advantage.Of course, all of these various perservative brews addtract/repulse bugs tovarying degrees, which can confound sophisticated statistical analyses. Theis quite a literature on this with regard to pitfalls and carabids. The bestsolution is to be consistent within sampling protocol for data you plan tocompare.James Bergdahl
bergdahl@icehouse.net

Attracts but doesn't kill. Which might be considered a negative factor, butI'm often trapping under permit on National Park or National Forest landsand they are concerned about the furballs. Using propylene glycol avoidsthat. I use straight glycol, enough to fill a 7 oz cup 1/3 full. And thetrap is under a cover (I use a earth-tone ceramic tile), raised about a cmabove ground level. I've never had a trap run dry in three months and havegenerally found them still wet after 6 months. In one set I couldn't get tofor a year (the way in, I won't call it a road, washed out) about half ofthe traps were still damp enough for the material to be salvageable.

>As I mentioned, if one decides to go with glycol, adding a little formalin will certainly make it taste> very bad. Also, I have always thought invertebrates "perserved" in just glycol were "mushy".

I've never had any problem that way. Spiders, sopugids, scorpions, and such remain quite useable, so long as they are completely in the fluid.

> I too have frequently left traps out for many weeks, even months,> but I have trapped mostly in temperate forests of Pacific Northwest. The evaporative> potential of pan traps vs. pitfalls is significant becasue of the difference> in surface area:total fluid volume. Depending upon climate and exposure, the> composition of trap fluids may be adjusted to meet needs. At least in my> area, pitfall trap in most habitats need only very dilute formalin. In cool> mountane habitats traps can be left out easily for two months, otherwise one> month is better. Of course, the larger the interval the less information on> phenology.

True. I like to use a 2 week interval. But there is often a chance to gettraps into a remote area if you can leave them for three of four months.

> Foramlin will not necessarily completely solve the mammal problem, but in> general they will not destroy the entire trapline, as I have seen them do> with glycol. Black bears can be especially troublesome.

My biggest problem is introduced primates. Especially the male huntingpacks that form in the fall. Otherwise the main problem is groundsquirrels. Coyotes don't seem to be interested in the trap is covered.William L. Pratt,
prattw@nevada.edu

A friend designed a cheap pitfall trap for use on flat rocks, and it seems tofunction well. Requires two plastic cereal bowls 6.5" wide x 2" deep, a glassMason jar 2.5" deep, a standard Mason jar screw top, and some wood screws 1.5"long. Cut a hole in the lower bowl and fasten the Mason jar screw top so thatthe jar can be screwed in beneath the inverted bowl. Scratch the outside ofthat plastic bowl well to make a rough surface that insects can easilynegotiate. With about 4 screws, fasten the upper bowl upside down 1.5" abovethe other, to fashion a roof to keep out rain. Pour Lotox antifreeze into theMason jar, screw it into the screw to, and place the entire contraption onto therock. It worked for me.Jan
From: Janet &/or Alex Ciegler
ciegler@infi.net

This is a topic that might benefit from broad input based on experience. I would like to hear more from others.

Traditionally, pitfall traps (which vary greatly in physical design) contain three components; water, a preservative, and a surfactant (to reduce the surface tension of the fluid and enhance capture).

I use a 25% propylene glycol solution (that is, 75% water and 25% propylene glycol) as a preservative. Propylene glycol is commonly used as an antifreeze and as such will not quickly evaporate from the traps (alcohol would be a poor choice in this regard). Further, propylene glycol is less toxic to vertebrates as compared to the commonly used ethylene glycol. As I have to clear all details of my field work with an animal ethics committee this is a bonus. I have held some ants in this solution for months with little deterioration in their condition (although some very soft ants such as _Tapinoma sessile_ have been not done well).

Regarding the surfactant, commonly a drop of unscented soap is used. I have stopped using this in my pitfalls because I can never be certain of the components of these soaps and can seldom find the same brand twice. My concern is that the soaps are seldom really unscented and one cannot be sure how they will bias the capture (they may attact or repel some ants). I have been intending to study the capture efficacy with and without a soap surfactant but I have no shortage of ants in my pitfalls.

The pitfall cup design that I use is a simple plastic cup with a snap on cap. The cups have an upper diameter and depth of 8cm. I punch 6mm holes around the upper edge of the cup using a simple stationary one-hole punch. This restricts access to the traps to small invertebrates (all ants) and stops the bycatch of small mammals as well as stopping mammals from drinking the solution (again a good point with animal ethics committees). To see a picture of this pitfall in the ground go to (here I insert a warning that this is a webpage in the very early stages of development):

http://www.cariboo.bc.ca/schs/biol/FacPgs/rhiggins/

Pitfall design is highly variable in the literature. If a norm can be said to exist it would likely be an open cup with a raised cover to prevent rainfall from swamping the sample. I've compared my design to the 'norm,' and found them identical in capture.

I'd like to hear from others about this topic.

regards

Rob

Robert J. Higgins, B.Sc., M. Sc.
Biology
University College of the Cariboo
Suite 303-383 Oliver Street
Williams Lake, BC
V2G 1M4

Ph. (250) 392-8176
FAX (250) 392-4984

AND

Robert J. Higgins, PhD Candidate
Natural Resources and Environmental Studies
University of Northern British Columbia
3333 University Way
Prince George, BC
V2N 4Z9

For pitfall traps that have to be checked more than once, I wouldsuggest 'double-cupping'. If you use containers that fit inside of each other,such as plastic cups or deli containers, you can cut the rim off of one cup andput it inside the other. This allows you to pull out the inside cup to checkthe trap while the outer one keeps the hole from caving in. This saves a LOTof re-digging time in any place with loose soil/sand.You can also live-catch and/or prevent larger critters from falling in with a,preferably clear, funnel in the top of the pitfall if you make the hole in itas big as the biggest critter you want to catch.I believe that the original thread asked about preservative for 4 days. Exceptin very hot weather, plain soapy water will keep things reasonably well forthat long and a saturated salt solution with soap will keep usually keep themin reasonable condition for a week even in hot weather, provided that there'sno dilution by rain. As was mentioned, propylene glycol is great. It issomewhat expensive, but reuseable if you strain out the insects through a finemesh sieve. Alcohol is pretty much worthless most of the time as, even besidesthe odor and expense, it evaporates far too quickly and at different ratesunder different conditions.As far as soap, if everything is uniform between the control and treatmentwithin an experiment, would any scent matter as much as insects floating on topof the preservative and escaping?--David Almquist (Entomology Geek)

I have read your message about pitfall traps with great interest, as I liketo employ this method of collecting. My main interest is the Scarabaeoideaand I trap mostly for coprophagus scarabs.

I have found that the bigger the trap ,( within reason of course) the betterthe catch. I use 9 litres plastic buckets with appr. 200 ml of glycol/watermixture and a small plastic cup within the bucket with various bait. I weighthe cup down with a small piece of rock, and place it in the middle of thebucket or hang it on the side of it by a small wire hook. I use a 15mm x15mm wire mesh to cover the buckets , so no small mammals can fall in.They neverdo.A compressed fibro lid is placed on top of the buckets to keep rain out.The traps are placed in a place ( it is on private property) where no stock( cattle or sheep) could step into them. Dingoes occasionally dig them up,but only if human faeces is used as bait.For bait I usually use pig or human faeces, occasionally fresh vombat dung,if I can get it.The best bait seems to be the faeces of any marsupial, takenfrom a fresh carcass. It sounds gruesome, but unfortunatelly, we have plentyof those on our roads.Australian coprophagus scarabs do not like baits whichare often used successfully in other countries ( e.g. rotten fish, meat,cowdung etc.). Only a very few native spp. would go for the dung of domesticanimals.Peculiarly, human faeces seems to be a good general bait, just thatit is not the nicest substance to handle.

It would be great to find an artificial scent which would imitate the smellof human faeces. It would make the task of baiting much lessunappetising.Does anyone knows about something like this?

I also use vinegar ( not the cheap kind, which is made of acetic acid andwater, but the more expensive kind which is made of natural substances, suchas wine or cider) and beer ( bottled, not in a tin or aluminium can). Thesebaits are good for Carabidae mainly.

I hope you ( and perhaps others too) will find these bits of info handy.Cheers,George Hangay

We have used rock salt and water, with a few drops of Tween20 for
surfactant, in pitfall traps with very little trouble for 6 years. Our
traps remain in the field for a week and we use them throughout the
summer in south Georgia, USA, where it can be quite hot. We
have had occasional problems with evaporation (although no more
than we experienced with other solutions), but the specimen
preservation has been very good and there is no odor (other than
that emitted by the occasional mouse or toad that winds up in the
trap.... :o( )

John

John R. Ruberson
Department of Entomology; University of Georgia
Rainwater Road
Tifton GA 31794
Phone: 229-386-3374; Fax: 229-386-3086
e-mail: ruberson@tifton.uga.edu

We have used both propylene glycol and salt as a preservative in pitfall
traps. These traps are emptied weekly or twice-weekly. Preservation
using either fluid is good. Evaporation can be a problem with salt
water, but this is easily corrected using deeper reservoirs.

I now favour use of salt for two additional reasons.
1) Specimens are easier to clear prior to identification - we find it
easier to remove residues from specimens sitting for extended periods in
salt water versus propylene glycol
2) Less concern re: liability - traps located on public or private
lands may have their preservative ingested by livestock or pets. The
owner of an animal that dies on the property may identify your
preservative as the cause. If so, easier to defend against this claim
if preservative is salt water, even though propylene glycol also is
non-toxic.

Also, I've often wondered whether the odour of propylene glycol affects
trap catches; i.e., preferentially attracting certain types of insects.
If so, this is probably less of a concern using salt water.

Cheers!

Kevin


Kevin Floate, Ph.D.
Research Scientist/Chercheur scientifique
Insect Biocontrol / Lutte biologique des insectes
Agriculture and Agri-Food Canada / Agriculture et Agroalimentaire
Canada
Lethbridge Research Centre / Centre de recherches de Lethbridge
P.O. Box 3000 / C.P. 3000
5403 - 1 Avenue South / 5403 - 1ère Avenue Sud
Lethbridge, Alberta / Lethbridge (Alberta)
CANADA T1J 4B1

Telephone/Téléphone: 403-317-2242
Facsimile/Télécopieur: 403-382-3156
E-mail/Courriel: floatek@agr.gc.ca
Homepage/Site web:
http://res2.agr.ca/lethbridge/scitech/kdf/intro_e.htm

We use proplylene glycol, for its lower toxictity, and have compared it to ethylene glycol and seen no significant difference in trap yields (at least as far as ants are concerned). I have never used rock salt so I do not know how this compares.

To protect animals and children, consider using a modified Nordlander pitfall. This uses a snap on cap, with holes punched in the upper rim on the cup side. To see what it looks like, check the picture at:

http://www.cariboo.bc.ca/schs/biol/FacPgs/rhiggins/Pitfalls.html

One advantage of this design is that animals can't get their muzzle into the top (it is covered) and if pulled up by an animal (other than a child) it will tip over and the solution drains out the holes into the soil before any significant ingestion can occur.
It also excludes small mammals competely so you have no smelly surprises when collecting the cups.

I put a clod of earth/moss on the lid to keep the trap hidden from view as the shiny lids were attracting animal attention when I first started using this design. Sometimes this works too well and despite flagging tape or markers nearby I have to spend a couple of minutes finding it in an area of a few square metres. This should help keep kids from finding them.

Just a thought

Rob

Robert J. Higgins, B.Sc., M. Sc.
Biology
University College of the Cariboo
Suite 303-383 Oliver Street
Williams Lake, BC
V2G 1M4

Ph. (250) 392-8176
FAX (250) 392-4984

AND

Robert J. Higgins, PhD Candidate
Natural Resources and Environmental Studies
University of Northern British Columbia
3333 University Way
Prince George, BC
V2N 4Z9

I stopped by the Dollar Store and bought $7 worth of beetle trap components:
  3 six-chambered plastic spice jars, 6 tall plastic cups, 3 plastic mixing
bowls, and a package of six two-piece plastic champagne glasses. From these
parts I have now constructed three pitfall traps that can hold up to six
baits at once. In the spring, I'll dig them in and see what I catch.

I cut the top portion of the champagne glasses to make clear plastic funnels
that slip two-thirds of the way down inside the plastic glasses. One
plastic glass is trimmed to nest inside the other just below the rim to make
a removable beetle-catching liner. When the beetles drop into the nested
glasses, they fall through the funnel into the bottom of the inside glass.

I wanted the funnels in order to keep the beetles alive so I can observe
them before killing them. They won't be able to crawl up the sides, and if
they try to fly toward the light, the chances are slim that they'll make it
through the funnel aperature. For that reason, I thought the clear plastic
funnels would be most confusing to the beetles.

To minimize the loss of life and limb from beetle fights, I'll place some
moist hiding material in the bottom of the inside cup.

Using a table saw, I cut two continuous slits around the outside of the
plastic spice jars to allow scents to escape from each chamber. Then I cut
a section out of the middle of the jar and glued the top and bottom portions
together with plastic cement to yield a much shorter container. I attached
the snap-on plastic lids of the spice jars to the inside bottom of the
plastic mixing bowls using high-load mounting tape, so that, when the jar is
snapped into the lid and the bowl is turned upside-down, the scent container
is suspended. The bowl is then centered over the sunken pitfall trap and
held down with three big spikes with spacers keeping it a quarter-inch off
the ground.

Besides supporting the bait above the trap, the bowls will keep rain,
falling leaves and most vertebrates out of the trap. If a shrew squirms
under the bowl rim, the funnel aperature will keep it from feasting on
trapped beetles. I imagine I'll catch small salamanders on a regular basis,
through.

All sorts of things could be tried as bait: dung, fresh meat and fish,
rotting meat and fish, rolled oats, mollasses-soaked cotton balls,
turpentine-soaked rags, and anything else that any sort of beetle is
reportedly attracted to.

Jim McClarin
jimmcclarin@hotmail.com

I have operated pitfall traps (mainly dung baited) in the tropics for many years. I have used antifreeze (propylene glycol, less toxic to animals), but have now converted to simple dishwater detergent (brand probably insignificant) in water (about 1 to 30), mixed before use in plastic bottle.
This keeps specimens relaxed and clean! I have rarely left them more than 2 days, but all seem fine. I then strain in fine tea strainer, dump in white enamel pan & transfer to 70% isopropyl alcohol. Most specimens are easily mounted, genitalia extracted, and no brittle legs, elytral separation, or problems.
Dr. R.E. Woodruff, Florida State Collection of Arthropods, Gainesville, Florida 

Pittfall traps

Last modified on Tuesday, 12 November 2019