Moved from Spiny Tachina Fly.

The blackish "felty-gray" structures dangling beneath the aristae are the plump tips of the 3rd antennal segments, to which the aristae are attached dorso-basally.

The two gray-black, short-bristly structures projecting forward from the bottom of the face are "(maxillary) palpi". I believe the palpi function as taste organs, and perhaps help manipulate food sources during feeding. Below is the description of these from Arnaud's 1951 paper on Paradejeania (see "Print References" on Info page):

"Palpi about 0.84 eye height; yellow-brown in ground color, silvery at certain angles; basal third narrowed, terminal two-thirds spatulate (compressed laterally); black setulae on outer side, upper outer terminal half much closer setulose than lower half, inner side without setulae except for terminal inner edge. Haustellum about 0.89 eye height, blackish brown; labella short yellow haired."

The term "haustellum" can be confusing. Some authors seem to treat it as synonymous with "proboscis" (= extensible mouthparts), or at least with the tubular food-sucking portion thereof. I think Arnaud used it to refer to the distal tubular portion of the proboscis. In particular, with that interpretation his "0.89 eye height" measurement would make sense in reference to your photo here. In that image the two palpi are projecting forward to the right, and appear reddish-yellow underneath. Below and to the left of the palpi, you can see the proboscis extended between the front legs toward the right-most flower head. The base of the proboscis is long-triangular and reddish. The thin, black, needle-like distal portion is what I believe to be the haustellum. That's about "0.89 eye height".

There are wonderfully detailed, diagrams of dipteran head structures on pg 19 of the "Manual of Nearctic Diptera(1)" (free PDF here). But, that reference seems to avoid the term "haustellum".

At any rate...Thanks for posting this nice series of detailed reference images for this very interesting tachinid!

(And I hope my verbose attempt at clarifying the structures was comprehensible! :-)