The Very Handy Manual: How to Catch and Identify Bees and Manage a Collection
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- Propylene Glycol Cup Trap
Glycol Pan/Cup/Bowl Traps(Information Provided by Dave Smith – FWS) – As part of a native pollinator inventory, I have been looking for a reliable pan trap method. I initially used two-ounce Solo cups with soapy water at five sites along an elevational gradient north of Flagstaff, Arizona. In order to increase the opportunity to sample a higher diversity of species, I decided to leave the traps out for a week. I substituted recreational-vehicle-antifreeze-grade propylene glycol in 12-ounce plastic bowls since it was obvious soapy water would not last long enough. Unfortunately, summer temperatures and low humidity caused the bowls to dry up and blow away before a week had expired (I can make someone a killer deal on a couple thousand 12-ounce plastic bowls). I changed from 12-ounce bowls to 12-ounce heavy plastic “stadium cups”. Each cup, painted either fluorescent blue, fluorescent yellow, or left white, is attached to ½-half inch PVC pipe with a 5-inch hoop cut from a plastic culvert pipe (see photo below). The stadium cups are very sturdy and are likely to hold up for a long season or two (or three) of sampling. The hoop is attached to the PVC pipe with a bolt and lock nut. The pipe slips over a piece of rebar set into the ground. The hoop is set high enough so the cup rests about 3 inches above the ground. If desired, a trap number can be written on the white plastic hoop. In order not to confuse the issue by having insects attracted to the white PVC end up in the blue or yellow cup, I painted the tops of holders the appropriate color for the cup it would hold. The top of the pipe is plugged to prevent bees from crawling down inside and getting trapped. The cups, filled halfway with the 50% industrial grade propylene glycol (50 water:50 propylene glycol) easily lasts for a week. The cups do not sit on the hot ground (air passes under them) and deeper cup lip and deeper fluid level slows down evaporation. I remove the cup from the hoop and dump the sample into a sieve. Leftover propylene glycol is collected in a bucket when the sample is poured through the sieve. The sieve is dumped into a plastic jar with alcohol. I use an automobile oil funnel to dump the sample into a labeled Whirl-Pak. Funnels with a wide opening can be found at auto parts stores. I also find that collecting samples goes much faster if the labels are pre-cut and placed in the Whirl-Pak beforehand. The BIML lab has taken the above technique and modified it slightly. You can view a YouTube video for how to deploy these at: http://youtu.be/z0DAY7bNOR4 and you can view how to make the stands at: http://youtu.be/x87CXM7mq54 and you can read a pilot report on using these in long-term monitoring at: ftp://ftpext.usgs.gov/pub/er/md/laurel/Droege/Draft%20USFS%20Glycol%20Report%2022711.docx. Glycol traps have the following advantages: They catch bees continuously, thus circumventing problems of shifts in phenology from year to year. Once deployed, they are easy to tend and the times for tending the traps can be scheduled rain or shine. They can be associated with weather stations where other devices are also tended regularly. They provide a continuous record of bees in the area. 
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