Unlike beneficial parasitic wasps, hornets attack honey bees, steal honey, invade bat houses, girdle branches, and ruin summer picnics.
So why would we want to tolerate hornets in the garden? What good can they do? Let’s find out!
Worldwide, there are 22 hornet (Vespa) species, including:
There are also 3 species of nocturnal Asian Provespa, which are not actually hornets.
Despite their name, bald-faced hornets (Dolichovespula maculata) are not true hornets, either.
There is only one true hornet found in North America: the European hornet (Vespa crabro). Introduced in the 1800s, this hornet is now found throughout the U.S.
Hornets are highly social insects. They live in large colonies, housed in papery hives, that are commonly built in dark crevices, such as dead tree trunks, under house eaves, and in your garage. Hives are made up of interconnected brood cells. Both the queen and workers can lay eggs. Fertilized eggs laid by the queen develop into sterile females, called ‘gynes’ while eggs produced by workers develop into males, called drones. Drones mate with the queen during ‘nuptial flights’. As a result, a hornet’s nest is largely populated by two nearly distinct gender-dictated populations. Workers care for the eggs as they move through larval and pupal stages, ultimately emerging as adult hornets.
Hornets and yellow jackets are both types of wasps, though yellow jackets tend to be smaller, with more yellow and black, while hornets tend toward more black and white or yellow and brown coloration.
Most hornets average 3/4” to 1”, while queens can be 1-1/2” long. If you look closely, you might be able to see that a male hornet abdomen has six segments, while females have seven segments and a stinging ovipositor.
Hornet stings and allergies
Like many other stinging insects, hornets become aggressive when they feel accosted (swung at, stepped on, sat on, that sort of thing), or when they believe their food supply or the colony are threatened.
Hornet stings are more dangerous to humans that other insect stings because they contain higher concentrations of acetylcholine. Hornet stingers are not barbed and can be reused many times. Also, when one hornet stings you, it releases chemicals that tell other hornets to sting you, as well. These same chemicals are also released when you kill a hornet or spray a hornet’s nest with poison, so be forewarned.
If you are allergic to stinging insects, you should always carry antihistamines or an EpiPen with you. Signs of an allergic reaction include shortness of breath, swelling of the face, lips, or throat, severe itching, weak or racing pulse, nausea, wheezing or gasping. If any of these symptoms occur, get medical help immediately. Call 911, grab a family member, or a neighbor right away. These symptoms can quickly escalate into a life-threatening situation. Otherwise, follow these steps to ease your temporary pain:
You can also take aspirin or acetaminophen to ease the pain, just be cautious about mixing medications, as that can cause yet another medical problem. Generally speaking, you are going to feel really miserable for 30 to 45 minutes, moderately uncomfortable for the rest of the afternoon, and you may experience discomfort for a week or so. You may also want to apply hydrocortisone or calamine lotion to the area. Pastes made of baking soda or colloidal oatmeal can also sooth the area. If you haven’t had a tetanus shot in the past 10 years, that can be a good idea, as well.
So, why would we want hornets in the garden?
Adult hornets feed on sweets, such as fallen fruit, sap, and your lemonade. They also collect insects for their larvae. This is part of the reason why they cause us so much grief during picnic season. From a hornet’s point of view, it is simply defending a food source when it refuses to back down from your burger and fruit punch. In addition to your picnic, European hornets commonly chew up beetles, dragonflies, grasshoppers and crickets, katydids, locusts, mantises, moths, and other wasps. This pulp is then taken back to the colony, where it is fed to larvae in the nest.
If you start having a hornet problem while dining outside, you can reduce the chance of stings by placing a plate of meat and fruit somewhat away from the picnic table.
If hornets become a problem around your home, try excluding them before poisoning them. Those chemicals tend to create more problems than they resolve.
You can grow a surprising amount of food in your own yard. Ask me how!
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