Spain, Greece and Washington – Stiletto Flies (Therevidae)

Quest for the Genus Thereva (Diptera: Therevidae)

by Kevin C. Holston

Getting out from behind the microscope or away from the computer is a welcome necessity in systematics research on Therevidae. The specimen material on hand allows us to get to a certain point in our research, after which additional data must be collected. This year I set my sights on taxa not in hand that I wanted to have represented in molecular studies of Thereva, to be conducted in Spring 2001. After the usual preparations in Illinois, I set off in late May to find Thereva Country and Euphycus Paradise, localities I predicted were in the Pacific Northwestern United States and Peleponnisos, Greece.

Before heading to Greece, I stopped in central Spain (May 25 – May 31) to look forChrysanthemyia rhagioniformis, part of an unusual assemblage of therevids found in the Mediterranean. Despite my best efforts and the assistance of Mike’s colleague, Alberto Fereres, I did not encounter any specimens of this species. I was, however, rewarded with specimens of four Thereva species, two of which were collected at this site near Mataelpino.

One of these Thereva species, which I have tentatively identifed as Thereva strigata, was conspicuous and active on the boulders pictured here – where I nabbed a few. The irregular surfaces and the activity of the flies made catching them a challenge. Otherwise, I collected the therevids here using malaise traps set out along the hillside and at a locality northeast of Madrid.

Males, like the one in this picture, flew up from the rock surface at incoming flies, but females were also collected from these boulders at lower positions. A macro lens would have been perfect for me at this moment, but I was happy enough to get it in the net a few moments later.

June found me in the beautiful mountainsides of southern Greece, where I found Euphycus Paradise in the lower valley of the Kuakiou River, Lakonia. Recently collected therevids from these Taigetos Mountains and the descriptions I had read of this region gave me confidence that I would find Euphycus speciosa somewhere in these hills. I placed traps at three elevations along the western side of the Taigetos range, following the highway that cuts through the mountains from Kalamata in the west to Sparta in the east.

At the lowest site, where the pine trees gave way to Mediterranean scrub, I explored the dry riverbed of the Kuakiou and found a therevid crawling on leaf litter from the plane trees overhead. It was Euphycus dispar, the target taxon of this trip, and I hurried to set up traps and try to get more specimens. Not only did I find this species, but I found hundreds of another of the Mediterranean endemics: Baryphora speciosa.

I was excited to see so many specimens of Baryphora speciosa, which is not well-represented in collections, and I was thrilled to see it in motion. Curated specimens from a museum gave little indication that this species would move around among the leaf litter, moss, and streambed gravel drinking moisture. These flies were very striking, with their wings held away from their bodies at an acute angle and their red abdomens decurved into a C-shape. Are they vespid wasp mimics? Good question…

During the few days I spent at this site, I was able to collect specimens of Thereva(4 species), Salentia (2 species), Pandivirilia (1 species), and three female specimens of an unusual and undescribed species. I set up three malaise traps rather close to each other to thoroughly sample this site while I collected near the traps by hand. Not only does this glimpse of the therevid fauna highlight the unique treasure of the Taigetos, but it underscores the importance of collecting in regions known to be diverse for the taxonomic group of interest.

insect specimens placed on map — All in all, the collecting in Greece was superb with more than I had imagined, as evidenced by the rows of insects I ended up with in my collecting boxes. There are quite a few insects I picked up while I was there that remind me that the Peleponnese insect fauna that should not be overlooked, even for Thereva.

therevid specimens — Notice all the therevids I was able to pin (note, not all specimens pictured are therevids)! I made sure I had species represented in alcohol first before collecting for dry material, and I was happy to have enough specimens for both. The new challenge will be identifying the material, which is why a trip to look at Therevatypes is scheduled for Fall 2000.

Mount Rainier with pines in foreground Not all the collecting this summer was so outstanding. I spent almost two weeks in Washington (11 June – 21 June 2000) looking for Thereva species without finding a single specimen. Only three specimens of Pandivirilia represent his efforts to collect therevids, but I was able to see the remarkable landscape of Washington along the way. Are these pictures of Thereva Country? I’m not sure that they are not, but I certainly didn’t find that enigmatic locality during this trip. As far as the North American fauna is concerned, I’ll have to rely on the kindness of strangers (and colleagues) for any more North American Thereva in alcohol. Strong datasets can always get a little stronger.