Nerius sp. (Diptera: Neriidae) - Campinas, São Paulo state, Brazil. ID by Fernando Carvalho-Filho.

I found this bizarre-looking fly outside of Campinas, Brazil (on the same tree as the Aetalion reticulatum that I showed earlier).  There were a few of them, and although they weren’t especially flighty they did have the annoying habit of constantly moving to the backside of whatever branch I tried to photograph them sitting on.  The tree (a small one with green, flexible wood and short, stout spines along the branches) was hanging on the edge of a hillside itself, so a period of careful branch-bending and precarious body-contortioning was required before I finally got one of the flies suitably placed within the viewfinder.  At the start and before all of my disturbance, they were perched head-downward and outward on the more vertically-oriented branches.

This fly is unlike any I’ve ever seen (or at least noticed), and I really had no clue to the family (or even superfamily).   I wish I could be happy just posting photos of interesting, though unidentified insects and be done with it, but something inside me doesn’t get much enjoyment out of that – I’m compelled to at least attempt an identification.  For my recent Brazilian exploits, I’ve found Flickr to be a useful tool in the identification arsenal – enter a search phrase such as “Brasil Diptera” and scan the results for any possible matches.  I don’t remember which particular phrase finally brought up a hit, but eventually I was clued into marsh flies of the family Sciomyzidae.  Another search for all Flickr photos tagged as such brought up several pages of more or less similar looking flies, including more than a few that were indeed very close matches.  My work seemed to be done.

Still, something about Sciomyzidae bothered me.  We’ve got sciomyzids here in the Midwest, and while there is certainly a resemblance, the overall gestalt of this and the similar appearing Flickr-ID’d flies just didn’t seem right.  So I opened up a broader search on Google images looking for more authoritative confirmation of the ID.  Eventually, I happened upon this photo by Brazilian photographer Enio Branco of a fly that, for all intents and purposes, looks exactly like mine.  The fly in that photo had been assigned to the family Neriidae (cactus flies), and further searching for information on the family in South America quickly turned up a recent faunal treatment of the family in the Brazilian Amazon (Carvalho-Filho and Esposito 2008).  According to that work, these distinctive flies can be distinguished from nearly all other acalyptrate flies by the antennal arista being situated apically on the postpedicel (third segment).  This character is readily visible on the fly in this photo and also on the similar appearing and apparently misidentified flies in the Flickr photos.¹  I figured I’d give the Amazonas key a go to see if an ID might be possible, but I immediately ran into trouble at the first couplet trying to decide if the antennal pedicel was elongate (Odontoloxozus peruanus), or if not whether the forecoxae were dark brown (Glyphidops spp.) or yellow (Nerius spp.) – they look light brown to me!  It’s entirely possible that this fly, photographed in southeastern Brazil, represents a species (or even genus) not included in the Amazonas key – hopefully one of the dipterophiles out there will be able to provide some insight.

¹ This could be an example of how one misidentified photo can create a growing pool of misidentified photos.  It serves to caution against accepting apparently solid IDs from open sources too quickly.

The most interesting feature of this fly (IMO) are the elongate head and legs with spinose forefemora.  Although appearing raptorial in design, apparently the males of this family engage in rather spectacular sexual combat, rearing up on their hind legs and striking each other with their forelegs or the ventral surfaces of their heads, even attempting to place each other in a head-lock.  I regret that I didn’t get the chance to witness such behavior.

Photo Details: Canon 50D w/ MP-E 65mm 1-5X macro lens (ISO 100, 1/200 sec, f/13), Canon MT-24EX flash w/ DIY oversized concave diffuser. Typical post-processing (levels, minor cropping, unsharp mask).

Update 02/07/11: I just received the following message from Fernando Carvalho-Filho, lead author of the Amazonas paper referenced above. Dr. Carvalho-Filho was kind enough to reply to my query regarding the identity of this fly as follows:

Dear Dr. Ted,

Thanks for the message. Congratulations, your photo is marvelous! Great macro. The best photo of a Neriidae that I have seen. Your webpage is very cool and has good pictures. In my opinion, the fly is a Nerius. It is difficult to determine the species, since they are separated based on the thorax color pattern.

Regards,
Fernando

My appreciation to Dr. Carhalho-Filho for his identification.

REFERENCE:

Carvalho-Filho, F. S. and M. C. Esposito.  2008.  Neriidae (Diptera: Schizophora) of the Brazilian Amazon: New records of genera and species, and key to species. Neotropical Entomology 37(1):58–62.

p.s. An early 2-pt lead in the new BitB Challenge series to whoever provides the most correct translation of the title – your prize for making it through the whole post!

Copyright © Ted C. MacRae 2011