Together with a group of undergraduate students, I am comparing the trapping efficiency of standard pitfall cups and ramp traps. Preliminary results suggest that the ramp traps perform quite well. They catch a similar diversity of insects and don’t trap as many non-target critters like lizards and salamanders. But, we are still sorting and identifying samples from the Hopland Bioblitz, where we ran the traps, so I don’t have the final word yet.
The basic trap components are shown in the image above. The ramps are made from 5x7in sheet-metal flashing (on left) that you can buy at a hardware store in packs of 10. It would be cheaper to cut your own, but then you have to cut a lot of sheet metal, which is a hassle. For me, the precut pieces are worth it. Each ramp (in middle) has the sides bent up about 3/8in and a small tab cut and bent (image below) so that it fits and is held in the notch in the box. The box (on right) is a standard, empty pipette tip box with a notch cut out of each side. The lid is a handy, snap-on rain shield.
The sheet metal is slippery and so to make it rough and easy for insects to climb up, the inner surface of the ramp is painted with a mixture of metal priming paint and clean playground sand.
Assembled, the trap looks like the images above. When set up the field propylene glycol is put in the box. When you place the trap, be sure to push the ends of the ramps down into the dirt or leaf litter so that insects will walk right up the ramp and not go under it.
Building the traps takes more work than just going to the store and buying cups, but in the field, there is no digging, which means they can be set up quickly and easily. In the paper based on our study, we will explore in detail the pros and cons of each trap style, but it seems clear that ramp traps have a place in our standard insect collecting kit.