Favoritos de rongoetz

Background of sighting: Was sitting in a treestand (Hackberry Tree), when this fly landed on one of the branches in front of me (about 12-14 feet off ground).

I immediately knew it to be a Robber Fly, but no clue on the species so I took a photo with my phone. Unfortunately, I was only able to get one before it flew off.

Habitat was hardwood forest (Hackberry, Hickory, Oak) at the edge of an ag field (corn this year).

9mm long. I saw two of these wasps (both uploaded) at the same time. One dived onto the back of the other. I assumed they were male and female, but the antennae both have 11 flagellar segments, so they must both be males.

Well, this was a surprise! And a challenge to identify.

Many Pepsis wasps, including several of the U.S. species and those known from or near Louisiana, vary dramatically within species in their antenna coloration and wing coloration (Hurd 1952; Vardy 2000, 2002, 2005). Their body color, particlarly the metallic sheen, also varies with lighting. This all makes it challenging to identify them in photos and even in specimens. However, some have distinctive features, and fortunately this one does.

Out of 6-10 specimens observed feeding on flowers at this location, I caught three specimens (which gave off strong odors, as reported in the literature), all males with body lengths of 28-30 mm. In the single specimen shown here (BL 28 mm), the sternal hairs are arranged in two distinct and separated “brushes” on each side of Sternite 4, with shorter hairs on Sternite 5 arranged in a less-dense transverse line with looser clusters. The other two specimens are the same. The only species in the U.S. (and for the most part in the entire genus) known to have this distinctive morphology is Pepsis mildei, which occurs widely and abundantly from California to central Texas and southward to northern South America (Vardy 2005, especially his Figures 377-379 & 676). The photos here show this distinctive morphology from several different angles and with different angles of lighting to reveal the structures well. The subgenital plate, visible in some of these photos, also matches the morphology reported by Vardy (2005, in his Figure 382).

As far as I can tell from the literature, the only Pepsis species known from Louisiana before this was P. menechma, which has a thin transverse line of dense hairs on Sternite 4 and a bare or nearly bare Sternite 5 (Vardy 2000, 2002, 2005). The other species that occur in central to eastern Texas are P. thisbe, chrysothemis, and grossa, which all lack long sternal hairs on S4 and S5 entirely (Vardy 2000, 2002, 2005).

Therefore, although this is a substantial range extension for P. mildei, I think this identification is strongly supported by the morphology of Pepsis species according to Hurd (1952) and Vardy (2005).