Sialis Latreille

Wichard, Wilfried & Engel, Michael S., 2006, A New Alderfly in Baltic Amber (Megaloptera: Sialidae), American Museum Novitates 3513 (1), pp. 1-10 : 2-6

Genus Sialis Latreille

Sialis Latreille, 1802: 290 . Type species: Hemerobius lutarius Linnaeus, 1758 , by monotypy.

Protosialis van der Weele, 1909: 263. Type species: Semblis americanus Rambur, 1842 , by original designation. [recognized as a subgenus]

Ilyobius Enderlein, 1910: 381 . Type species: Ilyobius flavicollis Enderlein, 1910 , by original designation. [5 Protosialis ]

Nipponosialis Kuwayama, 1962: 329 . Type species: Sialis jezoensis Okamoto, 1910 , by original designation. [5 Sialis s.str.]

Protosiails Penny, 1977: 9. Lapsus calami pro Protosialis .

DIAGNOSIS: Adult with head prognathous and relatively flattened; compound eyes large, positioned laterally; ocelli absent; antennae filiform; mandibles strong, multidentate. Pronotum broad (width up to twice length), rectangular or trapezoid; meso- and metathorax of equivalent proportions and design. Legs moderately long and stout; tarsi pentamerous, fourth tarsomere bilobed (and heartshaped), with fifth tarsomere inserted near base. Wings well developed, with complete venation typical of the order; fore- and hind wings with Sc fusing with R 1 before wing apex, R 3 forked in Sialis s.str., simple in Protosialis , M 1+2 simple; forewing with M 3+4 forked ( New and Theischinger, 1993). Males with nine, females with seven fully exposed abdominal segments.

COMMENTS: The foundation for the classification and determination of species of Sialidae are the works of Lestage (1927) and Weele (1909, 1910). Weele (1909, 1910) established Protosialis as a separate genus. Later, Ross (1937) considered Protosialis a synonym of Sialis , and Whiting (1994) considered the group to be a basal subgenus. Today some authors prefer to retain Protosialis as generically distinct, but we consider it as a subgenus pending a comprehensive cladistic analysis of species in Sialidae . Unlike Sialis s.str., Protosialis has R 3 simple in both the fore- and hind wings while this vein is forked in the former group ( New and Theischinger, 1993).

TABLE 2 Comparison of Baltic Amber Protosialis

Sialis (Protosialis) voigti , new species

Figures 2 –8

DIAGNOSIS: The new species shows the diagnostic combination of features typical of the subgenus Protosialis ; i.e., R 3 and M 1+2 are both unforked in the fore- and hind wings and M 3+4 is forked in the forewing ( New and Theischinger, 1993). The new species can most readily be distinguished from the other Protosialis species in Baltic amber by the combination of R 2 forked in both fore- and hind wings and by M 3+4 unforked in the hind wing (table 2). In addition, R 4 and R 5 in both the fore- and hind wings are unforked.

DESCRIPTION: Female. Total body length approximately 11.5 mm. Integument imbricate and dark brown where evident; wing veins dark brown, membrane hyaline. Head about as long as wide, with large compound eyes positioned laterally on anterior half of head. Mandibles stout; maxillary palpi 5- segmented; labial palpi 3-segmented; other mouthpart structures not discernable. Left antenna with 28 antennomeres (i.e., including scape and pedicel), right antenna partial; flagellomeres of roughly equal size, each slightly longer than wide. Ocelli absent. Tarsi of typical pentamerous construction, with fourth tarsomere bilobed and heart-shaped (distinguishing feature of Sialidae , along with the absence of ocelli). Forewing approximately 14 mm in length; costal field weakly arched, giving wing a slender form; seven c-sc crossveins present before termination of Sc; R 1 running parallel with Sc (with narrow subcostal cell between them) before veins merge near wing midpoint; R 2 forked near wing apex; R 3, R 4, and R 5 simple at wing apex; M 1+2 simple; M 3+4 forked near wing apex. Hind wing with R 2 forked near wing apex; R 3, R 4, R 5, M 1+2, and M 3+4 simple (the last vein is easily seen in the right hind wing but challenging to discern in the left hind wing). Female terminalic sclerites as depicted in figure 6; sternite VIII with two, well-differentiated, lateral calli.

HOLOTYPE: Adult female in middle Eocene Baltic amber (figs. 2, 3); accession number KU-NHM-ENT, B-003; located in the Fossil Insect Collection , Division of Entomology , University of Kansas Natural History Museum, Lawrence, Kansas.

PRESERVATION: The holotype is on one side of a large, oval piece of clear, yellow amber of maximally 39 mm length and 20 mm width, with a mass of 3.3 g. In the immediate vicinity of the alderfly is a partial caddisfly (only the front half of the body preserved, the distal half of the body and the distal third of the wings are cut off) along the amber’s edge. The maxillary palps, antennae, and legs permit identification of the caddisfly as a species of Leptoceridae (Trichoptera) . The remaining and larger portion of the amber contains fine detritus and numerous stellate trichomes, characteristic of Baltic amber.

The alderfly is in remarkably good condition and, aside from being rather complete, is also well positioned in the amber, permitting detailed examination. The specimen has some Schimmel (a froth of microscopic bubbles) obscuring the integument in some areas, but none of it prevents identification. The right forewing is rather extensively damaged along its leading edge while the left forewing is complete, only slightly obscured near the apex of its posterior margin by the left hind wing being partly folded forward (figs. 4, 5). Both hind wings can be seen in ventral aspect and, despite a few minor folds and some obscuring by the abdomen, the venation can be easily discerned (figs. 4, 5). The legs are complete and preserved folded beneath the body. The right antenna is incomplete, but the left antenna is well preserved. The mouthparts are not easily viewed, except for the palpomeres of the labium and maxilla, which can be distinguished. The venter of the abdomen is easily examined, and the female genital sclerites can be sufficiently discerned (fig. 6).

ADDITIONAL MATERIAL: An adult female in middle Eocene Baltic amber (figs. 7, 8); specimen in the collection of Jürgen Velten, Idstein, Germany.

3. Ventral aspect.

5. Ventral aspect.

ETYMOLOGY: The specific epithet honors the late Peter C. Voigt (July 22, 1930 – November 25, 2004). Peter was the heart and soul of the Bernstein Arbeitskreis (based in Hamburg), maintaining strong contact with each member and sharing with all his great enthusiasm for every aspect of amber and its study. He is greatly missed .

COMMENTS: The genital sclerites are typical for species of Sialis (e.g., Ross, 1937; New and Theischinger, 1993; Engel, 2004). Sternite VII is large and sclerotized but is otherwise little modified. Structural modifications are predominantly located on sternite VIII. Typically in Sialidae , sternite VIII forms a narrow, transverse strip with various, species-specific modifications. In S. voigti sternite VIII consists of two calli that are well separated medially (fig. 6). The calli are particularly strong apicolaterally and their form reinforced by a strong medial depression. Tergite IX is enlarged and extends ventrally to the sides such that it can be seen in ventral aspect, the apicolateral margins bordering the gonapophyses of the ovipositor (fig. 6). Subapically on the ventral margin of each gonapophysis is positioned a minute stylus. Cercal calli can be seen lateral to the ovipositor.

Figures

Figs. 2–3. Photomicrographs of the holotype female of Sialis (Protosialis) voigti, n.sp. 2. Dorsal aspect.