ShadyGardens Blog

July 11, 2013

Dirt Dobber: Spider Killer

Filed under: Beneficial, daubers, dirt, diver, dobber, insect, killer, mud, predator, solitary, spider, wasp — shadygardens @ 2:55 pm

As children we called them dirt dobbers but this insect is also known as the dirt dauber, mud dauber, dirt diver, mud wasp, and solitary wasp. 

The dirt dauber is a bluish black wasp with a very thin waist. After mating, the dirt dauber builds a nest using mud, usually from clay. Here around our house, we have several types of dirt daubers, but the one we see most often is the organ pipe dirt dauber, which builds its nest in long cylindrical tubes resembling organ pipes.

What purpose do they serve? Dirt daubers are a beneficial insect that we like to have around the garden. They are predators, and they love to eat spiders. Well, any creature that kills spiders is a friend of mine. (Sorry, I know spiders are beneficial in the garden, but I come from a long line of arachniphobics). And that is why I allow dirt dauber nests to remain in the garage.

Each species of dirt dauber has its own favorite prey. The blue dirt dauber is the main predator of the black widow spider.

Adult dirt daubers stock their nest with spiders to feed their offspring. They prefer particular types of spiders and certain sizes too. They capture the spider by stinging him, not to kill but to paralize. Rather than choosing a couple of large spiders, they cram their nest with a couple dozen small ones instead. 

Dirt daubers are not aggessive and need not be feared since they rarely sting humans. They really should not be killed, but if the nest is in an unwanted place, you can use a putty knife to scrape it away. For more information on the dirt dauber, please visit

June 12, 2009

Beneficial Insects in Your Garden

When many people see an insect, the first impulse is to kill it. But not all insects are pests, and many are actually beneficial insects, meaning they do good things like eating harmful insects and pollinating flowers. When we use pesticides to control insect pests, we also kill the good bugs.

You probably already know Ladybugs or Lady Beetles are beneficial insects, feeding on aphids, scales, and mealybugs. But did you know that the larvae of ladybugs look like tiny little alligators and eat even more pests than their parents?

Lacewings are fragile-looking insects with delicate, lacy green or brown wings, large eyes, and long antennae. Their larvae feed on aphids, scales, mealybugs, whiteflies, and young caterpillars.

The Praying Mantis will eat almost any insect (yes, they will eat the good bugs too and will even eat each other!)

Parasitic Wasps are usually too small for you to see, but you might spot signs of their presence. If you find a crispy-looking brown, inflated aphid attached to a leaf, it was probably the victim of a parasitic wasp that laid its eggs in the aphid so its offspring would have something to eat when they hatched. You might also see caterpillars, cabbage loopers, or hornworms carrying around cocoons of developing wasps. Parasitic Wasps lay their eggs on the back of soft caterpillars so their young will have a convenient food source upon hatching. (Yuck!) It’s almost time to see the Tomato Hornworm eating up the leaves and even the green tomatoes on our tomato plants. The best control is to pick them off and destroy them, but if you see one with loads of small white things that look like clusters of rice, just leave it alone–the white things are eggs of the Parasitic Wasp!

Grandaddy Spiders, or you might call them Daddy Longlegs, eat aphids, mites, and other garden pests.

These are just a few of the many beneficial insects in our gardens. Beneficial insects can be purchased from mail-order sources, but you can attract them into your garden without purchasing them. The best way to attract these beneficial insects into your garden is to just plant more flowers and herbs!

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