Ode to the predacious ground beetles

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Predacious ground beetles in the garden are formidable looking creatures, especially if you’re a slug, Colorado potato beetle, or any other small pest within its grasp. They eat practically any small creature, as well as weed seeds, at times, which is another bonus. The only downside is they will eat earthworms if they happen to snag one. However, it’s a small price to pay for all of the good they do. It’s nice to know that such a large insect is on our side when it comes to battling bugs that might bother the flowers and vegetables.

Ground beetles are primarily nocturnal hunters. Although, they’re very easy to find when you’re working in the garden and you turn over a rock or disturb their resting areas. My boys love them because they’re so big you can nearly put a harness on them. When I had Sam hold the one in the picture, it was difficult to keep it still enough to focus. He commented on how strong it was.

Life Cycle

They have a pretty typical life. After the females lays eggs in the soil, either in the spring or the fall depending on the particular species, she will often stay close to protect them. After hatching, the larvae often have limited mobility, but are still heavy feeders. They spit digestive enzymes on their food that basically turns it to a liquid that they can suck up and consume. From larvae, they can go through 2 to 3 pupal stages, once again, depending on the species.

Ground beetles can thrive in many situations, although if they have a soft, mulched area they are happy little critters. They stalk or ambush their prey so the better they can move, the more efficient they are at snatching up the pests in your garden. They also need places to hide. The cool thing is when the beetles hide underneath rocks or other flat pieces of protection in the garden. Then, you know you’re not going to find earwigs there. What’s also kind of interesting is sometimes when the airborne hunters, like birds, go after prey on the leaves and upper areas of the plants. The prey are inadvertently knocked them to the ground serving them up to the beetles. So even though they don’t climb, the beetles are still able to access pest in the foliar regions.

As with all beneficial insects, it’s important not to overdose the garden with pesticide. Ground beetles are particularly sensitive to Bt (Bacillus thuringiensis). So, even a safer (at least to us) pesticide is potentially dangerous to these tough little predators. So be prudent when applying any pesticide and keep it contained as much as possible to the target species. Other than in worse case scenarios, it’s best to let the predacious ground beetles, as well as the other beneficial insects, take care of the problem for you.

Meet Amy Grisak

Amy is a freelance author and photographer in Great Falls, MT who specializes in gardening, foods, and sustainable agriculture. She provides information on every kind…

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