#Physocephala tibialis

[jenfoundabug]

Mating pair of Physocephala tibialis, a species of parasitoid fly, found near a large patch of flowers in Pennsylvania. These insects have an interesting (and somewhat horrific) life cycle.

The adult female will hide under flowers and wait for an unfortunate hymenopteran (bee or wasp) to visit. She then attacks the host by piercing its abdomen and laying a single egg inside. Once hatched, the larva will consume the host from the inside over the course of 10-12 days.

Right before the host dies, the larva sometimes manipulates the bee/wasp to bury itself, which offers extra protection from weather and predators. The exact mechanism of this behavior is unknown, and interestingly, the probability of it happening depends on the host species.

After the host dies, the larva pupates and overwinters inside the corpse. The newly emerged adult has a structure on its head called a ptilinum that it can inflate and deflate to bust its way out of the host and the ground (if buried).

[jonnysinsectcatalogue]

Common Eastern Physocephala - Physocephala tibialis

This post involves descriptions of parasitoid behavior with Bees as this insect's primary host. If you are squeamish regarding Bee parasitism, I recommend clicking on this random link to see another post from the blog. Otherwise, I offer the following information regarding this seemingly innocuously specie of mimicking Fly:

Before following up from an earlier post, here's a small refresher. This insect is a Thick-Headed Fly of the family Conopidae. They rely on mimicry of Potter Wasps and Thread-Waisted Wasps to dissuade predators from eating them, as otherwise they are defenseless flower-loving Flies. While they appear to have a sharp bayonet protruding from their face, this is actually a proboscis which they use to sip nectar. Alongside the nutritional value that flowers can provide, Conopid Flies value flowers for another reason: they attract pollinators which the females need in order to lay their eggs. In an earlier post, I highlighted that it is essential to know the differences between male and female Psychocephala Flies if they appear in your garden in substantial amounts. The male Flies have a blunted abdomen, while female Flies have an abdominal tip structured like a crushing claw. You can see an example of this claw-like structure in Picture 9. This "claw" is a combination of a structure called a theca and an extension to the abdomen's 7th segment. Despite the position along the abdomen, these structures are not used for mating and it cannot fold on itself to crush.

Now since it looks so menacing, what does that "claw" actually do? In a manner similar to a crowbar or prying tool, this Fly specie uses this claw to open a Bee's abdominal exoskeletal plates in order to jab an egg inside the Bee itself. Yes, you read that correctly. Moreover, this process can be done midflight or while a Bee is investigating a flower! If the prying is successful, a Fly larva will begin to parasitize the Bee host as soon as it hatches and develop within its body. If the immune system doesn't neutralize the laid egg, the growing larva can change the behaviors of the Bee for its own benefit for up to 2 weeks. The larva presumably does this using chemical secretions or similar mechanisms (this phenomenon is not well understood and lacks lab documentation). It breaks my heart to type it out, but this behavioral change can all finalize with the parasite directing to host Bee to bury itself in the ground in order to create a secure environment for its pupation. It's not just Bees are afflicted by this form of parasitism. Just as there are many branches in the Conopid Fly family, there are many hosts that can be pried open. While disturbing, this is just the life cycle of one of the many creatures in the circle of life. The best we as humans can do is monitor the Bees and stay vigilant for this parasitic pollinator.

Pictures were taken on July 30 & August 20, 2020 and July 15 & 21, 2021 with a Google Pixel 4.

[faguscarolinensis]

Physocephala tibialis on Itea virginica / Thick-Headed Fly on Virginia Sweetspire at the Sarah P. Duke Gardens at Duke University in Durham, NC

[alcnfr]

Thick-Headed Fly, likely (Physocephala tibialis)...

[tenderanarchist]

Physocephala tibialis

[celestialmacros]

Another cool fly.  A wasp mimic thick-headed fly (Conopinae,) possibly Physocephala tibialis

May 29, 2018

Southeastern Pennsylvania

[humanbyweight]

Thick-Headed Fly (Physocephala tibialis)

[adobe-outdesign]

[8/28/20] Common Eastern Physocephala, Physocephala tibialis.

shoutout to my ID book for pointing out that thick-headed flies are named that way because of their shape, not because they’re stupid

[platycryptus]

it’s weird fly hour and on today’s weird fly menu is this thing, Physocephala tibialis.

not only does it afford protection by looking like a wasp (and enjoys... waving?), these things are parasitoids of bees and wasps. This one is a male, but females have a clearly visible ‘can opener’ structure on their abdomen to pry open the segments of their victim’s abdomen and insert eggs.

[foulserpent]

look at this thick headed fly, pretty sure this is Physocephala tibialis. bad photo quality but its insane how good of a wasp mimic this is i was like “oh cool i dont think ive seen that kind of wasp before” but i see the weird pulsating mouthparts and its like alas, diptera

[udc793]

Physocephala tibialis is a species of thick-headed fly (family Conopidae) found throughout the eastern United States, often near flowering plants. The adult fly is primarily black with a yellow face and thin white stripes on the abdomen. It is commonly found along the east coast of the United States and is often found near flowering plants. (at Arlington, Virginia) https://www.instagram.com/p/ChD3bKgscqRGpbDCtXx6nVm6rNMkGST1n2c27U0/?igshid=NGJjMDIxMWI=

[jonnysinsectcatalogue]

Common Eastern Physocephala - Physocephala tibialis

With Potter Wasps finally introduced to the blog, we can also explore these curious Flies of the garden that were stumbled onto this year. These strange looking insects were drawn to the yard’s oregano and also seem to like perching on rose leaves as well. Akin to Hoverflies, these insects mimic other stinging Hymenopterans in order to avoid becoming someone’s dinner. The insects mimicked in this case are Potter Wasps which are a handy family to mimic since Wasps are likely to retaliate if disturbed. If the mimicry holds, the false warning allows this specie to enjoy flowers at their leisure. However, this specie of Fly is not a Hoverfly, and belongs to another Fly family altogether! To tell the two apart, this Fly has a long proboscis jutting from its face which it uses to slurp up nectar from the plants it visits. Hoverflies lack this proboscis; they lap up nectar with a spongy-mouthpart (this video here provides a great example of this feeding). This Fly belongs to a somewhat elusive family called Conopidae (Thick-Headed Flies). It’s an odd name considering the individuals photographed in this post, but that’s the family they were sorted into. 

While they share some behavior with insects like Hoverflies and Bee Flies, these insects have their own habits and traits. Firstly, a fun example of their habits is the piling behavior shown in Pictures 4, 6 and 8. It’s not necessarily that there is a mating pair going on, they might just be piling on each other for kicks. Unlike more common Flies, males and females of this specie aren’t distinguished by their eye placement. Instead, watch for the abdomen position and the structure of the abdomens to confirm a mating pair. Since the individuals on display here have rounded abdomens, it’s likely that we are seeing two males in a pile (which can get as tall as 3 or even 4 individuals). Why do they pile? Who knows, but it’s an odd behavior! Interestingly, there doesn’t seem to be much struggling or infighting during the process. I can only speculate, but it may be a vigilance behavior or somehow involve mate selection. While we know now what males look like, look for the abdomen to have a claw-shaped tip (curving downward) to identify a female. Such a clawed tip is for more than just for show, and we’ll dive into that behavior on the next posting of these Flies. It’s very important that gardeners keep an eye out on these Wasp-mimics in order to protect their Bees...

Pictures were taken on July 21, 28 and August 20, 2020 with a Google Pixel 4.

[brolookatthatcoolanimal]

Back in September, @Entemnein and I went #bugwatching together (with masks on and distanced)! Here is a thread of the friends we found! #ExploreTinyWorlds --- (1) Sachem (Atalopedes campestris) (2) Locust Borer (Megacyllene robiniae) (3) Great Golden Digger Wasp (Sphex ichneumoneus) (4) Common Eastern Physocephala (Physocephala tibialis)? (5, 6) Mating and resting water striders (Gerroidae); I'm not sure of the species (7, 8) mysterious tiny bees (for @am_anatiala) (9) Chrysanthemum Lace Bug (Corythucha marmorata) (10) Blue Dasher (Pachydiplax longipennis) --- #wildlife_perfection #wildlife_macro #wildlifephotography #wildlife #nature #macro_brilliance #macro_perfection #macro_highlight #macrophotography #macrophotos #invertsofinstagram #InvertOfTheWeek #invert_macro #natgeoyourshot #natgeowild #nature #naturephotography #wildanimals #insects #insectsofinstagram #insectphotography https://www.instagram.com/p/CHvLWPXsfcB/?igshid=1sy3z9z1vb1p5

[alcnfr]

A Thick-Headed fly, likely (Physocephala tibialis)...

[coolbugs]

Bug of the Day

Check out this cool thread-waisted wasp I found in my pollinator garden the other day!

(Just kidding, it’s a fly, not a wasp - a thick-headed fly, Physocephala tibialis. Did it fool you? It was definitely trying to ;-))