Tachinid Fly from Uruguay

Subject: I think it is a fly
Location: Uruguay
December 5, 2016 10:37 am
Greeting, last year I sent in a request and you were very helpful in identifying a bug for me, thank you for that!
On my walk this morning I saw what I thought were a few sick-looking bees so I snapped some photos. Looking at the pictures when I got inside however they look more fly-like to my untrained eye. Either way their bodies appear swollen and weird.
The only specimens I have seen are on these plants that attract mostly flies, bees, wasps, hornets, and beetles. It is mid-spring now and I have just noticed them for the 1st time this morning. The pictures attached are front, back, and top-down respectively. Thanks!
Signature: Louis

Tachinid Fly
Tachinid Fly

Dear Louis,
You are correct that this is a Fly.  More specifically, it is a Tachinid Fly in the family Tachinidae, a family whose members are parasitic.  According to BugGuide:  “Larval stages are parasitoids of other arthropods; hosts include members of 11 insect orders, centipedes, spiders, and scorpions. Some tachinids are very host-specific, others parasitize a wide variety of hosts. The most common hosts are caterpillars. Most tachinids deposit their eggs directly on the body of their host, and it is not uncommon to see caterpillars with several tachinid eggs on them. Upon hatching the larva usually burrows into its host and feeds internally. Full-grown larva leaves the host and pupates nearby. Some tachinids lay their eggs on foliage; the larvae are flattened and are called planidia; they remain on the foliage until they find a suitable host.”

Tachinid Fly
Tachinid Fly

Thanks again! You guys really know your stuff.

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