STRATIOMYIDAE

Grimaldi, David A., 2016, Diverse Orthorrhaphan Flies (Insecta: Diptera: Brachycera) In Amber From The Cretaceous Of Myanmar: Brachycera In Cretaceous Amber, Part Vii David A. Grimaldi, Bulletin of the American Museum of Natural History 2016 (408), pp. 1-132 : 19-20

FAMILY STRATIOMYIDAE

Soldier flies are conspicuous, found on flowers or in large numbers at breeding sites, and well represented on all vegetated continents. Woodley (2001) provided a world catalog of the species and genera and their classification, and an analysis of subfamily relationships based on morphology. His phylogeny proposed the following relationships: Parhadrestiinae ( Chiromyzinae ( Beridinae ( Antissinae + Exodontha + Clade 4))). Clade 4, what I am calling “higher” stratiomyids here, includes the remaining, familiar, and generally speciose subfamilies like Pachygastrinae , Hermetiinae , Sarginae , etc. Parhadrestiinae are highly relict, with two species from Chile ( Woodley, 1986); Chiromyzinae consist of 14 genera from Central and South America, and Australia; Beridinae consist of 33 world genera, which have been monographed ( Woodley, 1995). The study by Brammer and von Dohlen (2007), a molecular-phylogenetic analysis based on two gene regions, agrees in many respects with the conclusions of Woodley (2001), particularly about relationships of the basal subfamilies. Its main finding was that Chrysochlorinae appear quite polyphyletic, which is corroborated by their morphological analysis (Brammer and von Dohlen, 2010). The molecular study estimated the following divergence times: basal subfamilies diverging in the Early to mid-Cretaceous, and subfamilies of higher stratiomyids in the Late Cretaceous (66–80 Ma). As of yet there is no direct evidence for higher stratiomyids in the Cretaceous, though divergence of basal subfamilies during this period is likely. Higher stratiomyids are diverse by the Paleogene (Evenhuis, 1994), and modern genera by the Miocene (e.g., Grund and Hauser, 2005; Coty and Nel, 2013).

The morphological analysis by Arillo et al. (2015) found that Cretaceous stratiomyids were all basal taxa, possibly stem groups to living Stratiomyidae , though there was no resolution of relationships. Indeed, Cretaceous Stratiomyidae are distinctly plesiomorphic to all living taxa in the family with the exception of Parhadrestia James. This is generally true for wing venation, and where preserved (i.e., taxa in amber) for characters of the body.

Plesiomorphic venational features of the Cretaceous genera ( Cretaceogaster Teskey , Lysistrata Arillo and Grimaldi , Montsecia Mostovski and Delclòs , Normyia , n. gen., Narcissomyia , n. gen.) include the following:

1. R 2+3 branches off of Rs near the middle of

the segment between R 1 and r-m. In Beridi-

nae the base of R 2+3 is very near, opposite, or

even distal to r-m (this last state is common

in higher stratiomyids).

2. R 2+3 is mostly parallel to R 1, only slightly converging with it, whereas in Beridinae the apex of R 2+3 is abruptly turned costad, and in higher stratiomyids it is often just a short

transverse vein between C and Rs. Chiromyzinae have a long, sloping R 2+3.

3. R 4 is quite long in Parhadrestia and the Cretaceous genera, except for Cretaceogaster where it is short and the R 4 -R 5 fork highly asymmetrical as in Beridinae . In higher stratiomyids R 4 is often very short and crossveinlike. R 4 is lost in Chiromyzinae . Measuring R 4 relative to the length of R 4+5 -R 5, from where it forks with R 2+3 to the tip of R 5, R 4 is merely 0.13–0.31 this other segment in Beridinae (mean 0.17), in Cretaceogaster 0.26, in other Cretaceous genera and in Parhadrestia 0.33–0.55.

4. In all stratiomyids vein C ends at the apex of R 5 or slightly beyond. In Parhadrestia , Chiromyzinae , Beridinae , and Cretaceous genera R 5 and C extend closer to the wing tip.

5. The same taxa (above) also have two M veins instead of three (some beridines have three M veins, but these are usually abbreviated). Higher stratiomyids have three M veins.

6. In higher stratiomyids cell d is small, especially in length (L/ W 0.8 –1.6 [mean 1.3]). Cell d L/W in Parhadrestia and Cretaceogaster is 1.8 and 1.64, respectively. In Beridinae , Chiromyzinae , and Cretaceous genera cell d L/W is always greater than 2.0, sometimes significantly so (e.g., Narcissomyia 3.2, Lysistrata 3.4) (the exception is Normyia telescopica , n. sp., which is 1.75).

Important features of the body in the Cretaceous genera are the following:

1. Antennae never reduced, generally with eight flagellomeres that are tapered apically. Lysistrata apparently has seven flagellomeres, but this may be a preservational artifact.

2. Scutellar spines do not occur in Cretaceous stratiomyids, as is the condition in Parhadrestia and Chiromyzinae . Beridinae have scutellar spines, with the exception of two genera that are significantly subordinate within the subfamily, Allognosta and Microhadrestia , so this is clearly a loss. Higher stratiomyids have scutellar spines. 3. The amber fossils provide insight into an interesting character system, namely the transverse tergal grooves or sulci on the abdomen, which generally occur on tergites 2 through 5 or 6. This feature has been used to define the monophyly of the Beridinae , but the grooves also occur in Parhadrestia , some Chiromyzinae , all the Cretaceous species in which the abdomen is visible, as well as in the xylomyids in Burmese amber. I am inclined to think that transverse tergal sulci is a synapomorphy of Xylomyidae + Stratiomyidae , which was lost in modern Xylomyidae and higher Stratiomyidae .

4. Lastly, in the few male stratiomyids pre-

served in Cretaceous amber (including well-

preserved ones reported below), the male

genitalia are very similar to that of Beridinae

and Parhadrestia ( Woodley, 1995) : gonocoxa

stout (sometimes with mesal tubercle or

spine); gonostylus stout, also often with one

or more spines, as in the new Burmese amber

genera Normyia and Narcissomyia . Whether

the gonocoxites are fused or not to the hypan-

drium was not observable.

Gegantoberies liaoningensis Huang and Lin (2007) , from the Early Cretaceous Yixian Formation of China, is misassigned: it is definitely not in the Stratiomyidae , and probably not even in the Stratiomyomorpha , given the very long stem of vein Rs that forks from R 1 near its base. With the diversity and fine preservation of Stratiomyidae in Burmese amber, these fossils provide a unique window into the early history of the family.