#transverse hoverfly

Transverse Hoverfly - Eristalis transversa

In a similar vein to the Eastern Carpenter Bee post made earlier this week, today's post highlights the blog's YouTube channel's next insect. Year upon year this brightly colored specie returns to my backyard to hover in place while it flies around sampling the flowers. If not for their large, red compound eyes, their flight and striped pattern would be a perfect match for a small Wasp. However, unlike their stinging flower-mates, these Hoverflies are here to sample nectar and pollen, and in the process they contributed to flower pollination. It seems like open-faced flowers are the preferred flower for this specie since they are more accessible. A Fly like this one can simply lap up sustenance without having the crawl into a flower's opening.

While the rewards for the latter could be sweeter, depending on the flower (and its enticing aroma), perhaps a Fly also considers that it will need to take off from a suitable launch point. Moreover, it may not do well with wings compressed against the side of a flower as it ventures inside, defenseless as it is. Nevertheless, with a disguise as convincing as this, there aren't many insectivores that are fool-hardy or desperate enough to try and approach a Hymenopteran look-a-like insect from the rear! Eat well, beautiful Flies! If you find one (or a similar Eristalis specie): look to their eyes to make sure it's not a Bee, and don't be afraid to handle them (if positively identified). They're surprisingly light-feeling on the hand.

The Insect Highlights of 2023 - Jonny's Insect Catalogue

With the new year celebrations scheduled for this weekend, I thought it best to share some of my favorite insect specimens from this year, rather than one single variety of insect. The pictures here haven't been uploaded to the blog in a post, so today they can all share the spotlight. There are many familiar faces here and all of them are incredible and beautiful creatures. Hopefully there are even more insect delights and finds to enjoy in the upcoming year. To ring in the new year, we have the following insects:

Monarch Butterfly - Danaus plexippus - Order Lepidoptera (August 7th)

Green “Goldeneye” Lacewing - Chrysopa oculata - Order Neuroptera (July 26th)

Carolina Locust - Dissosteria carolina - Order Orthoptera (August 20th)

Dog-Day Cicada - Phymata pennsylvanica - Order Hemiptera (August 24th)

Milkweed Beetle - Tetraopes tetrophthalmus - Order Coleoptera (July 9th)

Red-Legged Grasshopper - Melanopus femurrubrum - Order Orthoptera (September 13th)

Eastern Carpenter Bee - Xylocopa virginica - Order Hymenoptera (June 5th)

Five-Banded Thynnid Wasp - Myzinum quinquecinctum - Order Hymenoptera (August 7th)

Jagged Ambush Bug - Phymata pennsylvanica - Order Hemiptera (August 20th)

Transverse Hoverfly - Eristalis transversa - Order Diptera (August 8th)

All pictures here were taken in 2023 with a Google Pixel 4.

Tranverse Hoverfly - Eristalis transversa

They’re back to visit the black eyed susans, blending in with the fellow pollinators of the summer. In this set of images, we once again find males and females enjoying the flowers and the sweet nourishment they provide. If you look closely at the images, you may notice a particular female with orange markings on the side of her abdomen in place of the usual yellow. The significance of the orange color is rather unclear (i.e. whether its a result of genes, nutrition, etc.) but it does give her an air of distinction. I can only speculate that maybe the orange markings help with its Bee-mimic disguise or serve as an indicator of its health, leading to more chances to mate. I don’t know, do all families of Fly use their visual acuity to assess their mates? With reduced antennae, maybe they need to? Looking at pictures other people have submitted on Bugguide, the orange colors can also manifest further down the abdomen towards the rear segments. Maybe this is just a case of general variation that bares little importance on what the adult Fly will look like. I may be repeating myself from an earlier post (and I apologize if I am), but when it comes to observing these Flies, best to just follow them around and record them and don’t bother trying to catch them. 

It is possible to catch them easily however. Despite their flying speed and control over their position, they can be caught in hand easily when investigating a flower or when at rest on a leaf. After you open your hand though, they will quickly flee...right back to the flower fields. If the Hoverfly stays on your hand for a good while, it’s a great photo opportunity so get recording and documenting otherwise I won’t believe you. Myself however, I’ve had more success letting them be on the aforementioned flowers and leaves. There they can be themselves as much as possible (the presence of a photographer likely puts them on edge). While looking at them this time and referring to notes from looking up insect identification, I noticed something new about their thorax. While the abdomen is the visual pleasing part of the insect, the thorax (in combination with the abdomen) is a key structure to successfully identify this Fly: the gray and black pattern on the surface is very distinct. For a comparative example, compare our Transverse Hoverfly friends to the rarer Narrow-Headed Hoverfly friends? Or perhaps look at another Eristalis specie.

Tranverse Hoverfly - Eristalis transversa

Today work got away from me, so without much time to edit and draft as much as I’d like: here’s a short video post featuring a lovely and familiar Hoverfly specie giving itself a thorough clean. Since it spends a lot of its adult life in the air, it has to keep its pair of wings clean for more efficient flight! Moreover, this Fly has to keep its 6 legs clean given the number of plants and surfaces that  will land on throughout the summer! Fortunately Hoverflies tend to be cleaner than most since they mostly spend time foraging on flowers rather than on refuse or decaying matter. Unlike what this video would give the impression of, I didn’t see too many of these Hoverflies in the late spring/early summer months compared to prior years. Instead, the insect featured in last week’s post was found more often: one of the many Thick-Legged Hoverflies. Although this may be just a one season anomaly, there’s always a worry that the latter might displace the Transverse Hoverfly in terms of small habitats, if only temporarily. This goes double considering that Hoverflies can be very territorial over meeting areas when mating is on the line and may drive competitors away. Even those of other species! This is still possible depending on resources available during the seasons, but I’m relieved as with the return of black-eyed susan flowers this summer, the Transverse Hoverflies have returned to forage as they have done once before. Hooray! Surely the two different Hoverflies can overlap without treading on each other over the years.

Transverse Hoverfly - Eristalis transversa

“Well hello there fellow Bees. What a lovely day it is to visit the flowers and enjoy the sun. Buzz buzz.”

These Hoverflies are a common sight in the garden and they have been for years now. There’s also a few flying around in search of flowers to obtain a meal from. Keep an eye out from them yourself, and be sure to remind yourself that they don’t have stingers! When in doubt, look for those large compound eyes and you’ll soon realize that those stripes are just for show. While they’re designed to fool hungry predators, I’m thinking that Bees and Wasps are a little more discerning, given they can identify their kin through scent and other means of communication. If the Fly is found out, it can still escape through quick aerial acrobatics. While the video fails to capture the hovering in place and the sudden short bursts during flight (which are tough to capture on film), we do get to see the Fly visiting flowers for a snack after cleaning off its feet and/or labella (sponge mouthpart) for a clean tasting.

Transverse Hoverfly - Eristalis transversa

Perched atop these black-eyed susan flowers, we find Flies wearing the colors of a  Bee. The mimic is very convincing but if you look closely enough at this insect, it’s impossible to avoid the characteristics that make a Fly a Fly (more accurately a Dipteran). Flies only have one pair of wings and a set of halteres to help control their flight and balance. As well, their head has a distinct Fly shape with large red compound eyes. Don’t worry, since these are Flies, they don’t have stingers and can be safely handled. They earned their name by their flight patterns; though relatively large, they are strong and agile fliers who tend to hover in place before darting off in a direction, then hovering again, and repeating to process until they find a place to land. Such a flight strategy could help them escape predators who see through their mimicry. Just like the bees they mimic, they do also serve as pollinators for the flowers that they visit. 

Observations: among these pictures you can actually see male and female Hoverflies, and they have a few differences to tell them apart. 

The female Flies’ compound eyes are slightly further apart than the males’ eyes due to a wider vertex. This also changes the location of the antennae and the distance between the ocelli (simple eyes atop their head). The males’ compound eyes are very close together.

Male Flies have an extra vertical black band in their patterning (towards the back of the abdomen) while females don’t have this extra feature