Collecting Carabus

Collecting Carabus

The genus Carabus occurs in a wide range of habitats around the world from snow and boulder fields (Orinocarabus, Oreocarabus, Iniopachus) through woodland and pasture (Carabus s.str, Chrysocarabus, Megodontus) and into streams and marshes (Ctenocarbaus, Hygrocarabus, Limnocarabus). This of course means that no one method will enable capture of all species and so we will set out the different techniques below and the type of species it should help you catch.

Pitfalls

Perhaps the most widely used and successful trapping method for many different groups, not just Carabus. These traps are well suited to eurytopic species, but can be used anywhere where you can dig a hole. These traps are more successful in late spring through to Autumn when Carabus are still above ground and active. If you are using them near rivers or in marshes/bogs you may need to place a weight in the trap to stop it being pushed out by the water table, or you can peg it in place with sticks.
Holes are dug in the substrate and a plastic cup is sunk into the ground until it is flush with the surface. Extra soil from the hole can be packed around the pitfall to make sure Carabus can’t fall down the side. It is generally a good idea to put traps out in a regular pattern with both ends discretely marked. For example place a stick in the ground for the first trap, walk 10 paces and place another and continue until you have set as many as desired. At the end of the line place another stick.
In continental Europe it is common practice to bait the traps with balsamic vinegar or red wine. There is anecdotal evidence that these fruity substances work as attractants and increase the trapping rate, but in the authors experience it does not make any noticeable difference in the UK. If you are not using bait you should still fill the traps with water (not alcohol, it will stiffen the specimens) and a little unscented detergent. If you unable to check the traps more than once a week you should add some salt to the mixture to aid preservation of the specimens.
Another method of improving trap returns is to use wooden or plastic cross-vanes. These are placed so that the two lengths intersect above the pitfall and help to increase the effective trapping area. On encountering one of these vanes a ground beetle will walk along it to find a way around. There is of course a chance that the beetle will walk the wrong way, but trapping returns should still increase.
Finally, some collectors like to cover their traps. This helps to keep the rain out and therefore reduces the likelihood of the trap flooding, it helps to conceal the traps from corvids and other birds who will raid the traps and it helps to conceal the traps from anyone else you don’t want to see them. Of course it can also conceal your traps from you and so you may want to consider GPS marking their position. These covers can either be precut plastic sheets placed on long nails, or pieces of tree bark on sticks.
Don’t litter and remember to remove your pitfalls at the end of the season

Winter collecting

Once the cold weather sets in and it becomes consistently cold the Carabus will begin to hibernate. In continental Europe this is one of the best times to collect Carabus, however it has not been successful for the author in the UK. The aim of this technique is to check the main hibernation spots for Carabus as outlined below:

• Old and soft tree trunks are good places to look and apparently you can often find large assemblages of a species in just one trunk. Carefully turn over the log and remove the soft bark. Return the log once you are finished.
• Look under large rocks and stones
• Look under the large blankets of moss that you tend to get on north facing banks.