A hoverfly is often confused with a wasp or bee (more commonly a wasp) because of their similar yellow and black coloring. This mimicry in coloring has likely helped the hoverfly survive – a technique called Batesian mimicry where a harmless plant or animal (or in this case insect) mimics the look of a more dangerous plant or animal. But there are some big differences that allow us to distinguish, on sight, between a wasp and a hoverfly.
There are around 6,000 species of hoverflies, according to my reference books, and over 100,000 species of wasps. The most immediately notable difference between wasps and hoverflies is the antenna. Most wasps have antennae like bull-horns that begin more on the sides of the head and protrude outwards. Hoverflies’ antennae usually begin more directly in the front of the head, and are much smaller and shorter (see examples of overfly antennae in picture 1 and 3, wasp antennae in pictures 2 and 7).
There are three other features that can allow you to immediately distinguish between a wasp and hoverfly. First, the abdomen of a hoverfly is often less round, having a somewhat flat appearance (see picture 1 and 3). Wasps have much rounder abdomens, and also have a ‘wasp waist’ the narrowing between the thorax and abdomen (see pictures 2 and 7). The third distinguishing feature are the spots – wasps often have pairs of spots along the back of their abdomen (see picture 2) and hoverflies do not (see pictures 1 and 3).
There are other differences that are not immediately apparent, but may help you distinguish between a wasp and a hoverfly.
1) Most wasps have two sets of wings, hoverflies have only one set (in picture 7, below, you can see the wasp has one larger, more dominant set of wings, and one smaller, thinner set of wings – at orange arrow).
2) In the hoverfly wing there is often a ‘vena spuria’, meaning a marking that looks like a vein, but is not. In picture 1, if you look closely, you can see it. The ‘vein’ ends, just before the edge of the wing, and is not connected to anything else, so it is not a true vein.
3) In picture 4, you see a close-up of a wasp’s head. In the center are the ocelli, or the three simple eyes of the wasp, formed in a triangle, as well as the two compound eyes on the side of the face.
Hoverflies and wasps do similar things – they’re both useful in natural biocontrol. Aphids and other plant-eating insects can destroy crops and cost hundreds of thousands of dollars in damage every year. Adult hoverflies feed off of only nectar or pollen, but the maggots (babies) of hoverflies feed off of a variety of things. Some eat decaying plant or animal matter which makes them useful in breaking down that matter into nutrients that plants can use. Some are insectivores, eating things like aphids or other plant-eating insects which make them useful as biocontrols. Adult hoverflies lay their eggs next to sources of food that will become food for the maggots, such as in the middle of an aphid colony.
Hoverflies can neither sting nor bite. They do not have stingers, and their mouths are formed more for mopping up substances than for biting. They can cause the disease Myiasis in sheep and (very rarely) humans. It’s caused by the maggots feeding off of feces or open wound areas, generally only where there are poor sanitary practices is this disease ever an issue. It’s common practice to remove a sheep’s tail early in their life, to help prevent this disease as well as others.
One type of hoverfly, the Narcissus bulb fly, is not beneficial in a garden. It lays its eggs on the stems of bulb plants (such as amaryllis, hyacinth, lilies, tulips, etc.) as the flowers die back in the late spring. The Narcissus bulb fly, though it’s a type of hoverfly, differs from other hoverflies because instead of eating aphids, the maggots prefer the pollen and nectar of certain bulb flowers. After hatching, the maggots of the Narcissus bulb fly will eat away at the bulb, causing damage and death to your flowers. If your bulbs do not grow in the spring, dig some up and cut them in half. If it is hollowed out to some extent inside, and/or you find a dirty, cream-colored plump maggot inside, your bulbs are infected with Narcissus bulb fly. Since it is not of much value to you in the garden, not being a predatory insect, the best thing you can do is to get rid of it.
Wasp larvae, like most of the hoverflies, also prey upon insect pests. I don’t know of any pest that doesn’t have at least one type of wasp as its predator. Adult wasps generally feed only on nectar, same as the hoverfly.
The typical wasp is viewed as large and aggressive, though many species of wasps are so small you probably have never noticed them – as small as 1/100th of an inch. Some wasps, especially yellowjackets or paper wasps (wasps that construct papery nests of chewed up wood) can be aggressive. But most wasps are not. (The picture to the left shows paper wasps constructing a nest – if you look closely you can also see an egg inside each compartment.)
The problem encountered with wasps is that they do like sweet things, which makes them attracted to picnics or ripened fruit, wherever they have access to anything soft and sweet. They will eat softer fruits, such as plums, peaches, etc. where they can break through the skin of the fruit, as well as apples or other hard-skinned fruits if there is already an opening created (likely by a bird or other animal).
If you’d like to attract hoverflies to your gardens, try planting a type of alyssum, static, yarrow, Queen Anne’s lace, or any of the flowering umbelliferae family (anise, dill, fennel, etc.).
The video below is one that I put together for kids. It’s a collage of video clips of pollinators (butterflies, bees, and hoverflies). There are a couple of particularly good clips of hoverflies in it.
Photo credit for picture 5: http://www.geller-grimm.de