Beneficial Beetles

Beneficial Beetles

One of the most common and yet widely unknown beneficial insects on our landscapes is the common black ground beetle (CBGB), Pterostichus spp.. The dullish appear and nocturnal and reclusive behavior is partly to blame for their obscurity, in spite of all of the great benefits of their inclusion in our landscapes. These incredibly valuable players in our gardens will only turn up when you disturb the land, weeding, digging etc.

CBGBs, as pictured above, are about 1/2 inch long with distinctive head, thorax and abdomen which are shiny, black and ridged running the length. In the late summer, females will lay eggs underground, larvae will overwinter there feeding on other subterrestrial insects, weather permitting. Adults will inhabit weedy patches, brush piles and other dark, moist places emerging only at night to forage for grubs and maggots and other terrestrial insects. What black ground beetles lack in physical beauty and demeanor they account for with ingenuity and speed.

These beetles are not known to fly, they run, or rather, they sprint in order to catch prey and evade predators. CBGBs hunt preferentially in relative seclusion, under mulch piles or thick vegetation only venturing into the canopy for the chance to grab a juicy caterpillar or aphid. Predators which mainly hunt in the canopy sometimes flush prey out of trees and onto the forest floor, paving the way to a delicious meal for the CBGBs with minimal effort exerted. Together, ground beetles and their canopy-hunting analogs reduce total pest numbers more than either could do on their own.

Helping to maintain a healthy population of one beneficial insect will help others. Flowering, nectar producing plants attract flying hunters, driving terrestrial insects underground where they may become prey for soil dwelling insects. Loosely applied mulch is also helpful as it provides refuge for beneficial insects from daytime heat and sun. An interesting cultural method for controlling turf pests is to install an “insectary strip” within your landscape; this consists of a patch or strip which you let go to weeds, or plant with wildflowers or or plant taller grasses that may attract predatory insects to your landscape to control pest populations.