Common Eastern Physocephala

Common Eastern Physocephala

Physocephala tibialis

Daily sighting probability ~10% · With luck
at Boston

In 3 days ~30% in a week ~50%

241 Verified sightings at Boston
40 In all 2 parks From 2019 to 2026
August Best month
☀️ Diurnal When it's spotted

About the Common Eastern Physocephala

Physocephala tibialis, the common eastern physocephala, 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.

P. tibialis flies parasitize many different species of bees by laying their eggs inside the abdomen of their host. The larva hatches inside of the host and grows and develops until it takes up the majority of the host's abdomen. The host then dies and the larva envelopes itself in a puparium and pupates inside of the corpse. After an extended period of pupation, the adult emerges from the corpse of the host bee. When a bee becomes parasitized by a P. tibialis larva, certain behaviors such as induced grave digging and changes in flower preference often occur.

P. tibialis is found in North America, primarily along the east coast of the United States. They can be seen as far north as Massachusetts and as south as Florida. They have also been seen as far west as Wisconsin and Texas.

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Global Distribution

Parks Where Found

# Park Country Daily sighting probability
1 Shenandoah National Park 🇺🇸 United States
~10%
2 Great Smoky Mountains National Park 🇺🇸 United States
~10%

Cities Where Found

# City Country Daily sighting probability
1 Boston 🇺🇸 United States
~10%
2 Minneapolis [Saint Paul] 🇺🇸 United States
~10%
3 Philadelphia 🇺🇸 United States
~10%
4 Baltimore 🇺🇸 United States
~10%
5 New York City 🇺🇸 United States
~10%
6 Washington 🇺🇸 United States
<5%
7 Toronto 🇨🇦 Canada
<5%
8 Chicago 🇺🇸 United States
<5%

Before you go

What are the chances of seeing a Common Eastern Physocephala in Boston?

With luck

About 10% of wildlife watchers report a Common Eastern Physocephala sighting in Boston on a given day, based on 241 verified sightings from GBIF citizen-science data. It is the 67th most-seen of the 1200 insects we can rate there. Over three days the chance rises to about 30%, and over a week to about 50%, if each day is a fresh chance.

When is the best time to see a Common Eastern Physocephala in Boston?

July to September

In those months about 20% of wildlife watchers report a Common Eastern Physocephala in Boston on a given day, against under 5% in October to May, the lowest months.

What time of day is best to see a Common Eastern Physocephala?

Between noon and 3 pm

Across all the parks we cover, that three-hour window holds the most Common Eastern Physocephala sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.

Is Boston the best place to see a Common Eastern Physocephala?

Yes

Of the 8 cities where we can rate Common Eastern Physocephala sightings, Boston has the highest daily chance: about 10%. Next come Minneapolis [Saint Paul] (United States, about 10%) and Philadelphia (United States, about 10%).

Where does the Common Eastern Physocephala sighting chance come from?

GBIF citizen-science records

It is estimated from how often the Common Eastern Physocephala is recorded against all the insects logged in Boston (241 verified sightings), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.

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