Lasius schiefferdeckeri

This is the predominant Lasius of the Baltic amber deposits.

Identification
See the description below.

Distribution
This taxon was described from Baltic Amber (Eocene).

Faunal relationships
Lasius schiefferdeckeri was apparently one of the most abundant ants of Baltic amber times, since it composed 1172 out of the 11,678 amber specimens collectively studied by Mayr, Andre, and Wheeler (Wheeler, 1914). It was surpassed in this respect only by Ctenobethylus goepperti, Yantaromyrmex geinitzi and Formica fiori. Wheeler found workers included in the same block of amber with Ctenobethylus goepperti and Cataglyphoides constrictus. In the absence of further data it may be contended that Lasius schiefferdeckeri was a member of a warm temperate fauna, possibly segregated by elevation or latitude in the extensive amber forest region. Its presumed derivative species, the members of the modern niger complex, have continued to thrive in the Palaearctic Region, along with species of Stenamma, Leptothorax, Formica, and Prenolepis, at the same time that numerous other amber genera have withdrawn to tropical regions or declined to total extinction. (Wilson 1955)

Nomenclature

 * †edentatus. †Lasius edentatus Mayr, 1868c: 46 (m.) BALTIC AMBER (Eocene). Junior synonym of †schiefferdeckeri: Wilson, 1955a: 52. See also: Dlussky, 2011: 211.
 * † schiefferdeckeri. †Lasius schiefferdeckeri Mayr, 1868c: 44, pl. 1, fig. 2; pl. 2, figs. 27-32 (w.q.m.) BALTIC AMBER (Eocene). Senior synonym of †edentatus: Wilson, 1955a: 52.

Description
Wilson (1955) - Wheeler (1914) offered the opinion that Lasius schiefferdeckeri is very close to the modern species Lasius alienus ("niger var. alienus" and "americanus"), differing only by its smaller size. The present study has shown that size differences are actually insignificant but that schiefferdeckeri does exhibit variation in scape index transspecific for most of the modern members of the niger complex, as well as a peculiar male mandible structure intermedate between the primitive pallitarsis type and advanced niger type.

Worker
Wilson (1955) - (1) Size range and mean, clypeus, mandibular dentition, and appendage pilosity similar to alienus.

(2) ML exceeding EW.

(3) SI very variable, ranging in value from typical Lasius emarginatus through typical (northern European) Lasius niger to typical Lasius brunneus.

Male
Wilson (1955) - (1) Very small, at lower limit of alienus size variation.

(2) Mandible form showing great variation which brackets both the Lasius pallitarsis and niger types, a condition also encountered in the modern species Lasius flavus.

Specimen no. 1. Subapical cleft of mandible present but shallower than in pallitarsis; masticatory border flat; basal angle intermediate in development between pallitarsis and niger. HW 0.77 mm., sr 85. sr very high with respect to modern members of the subgenus, above the emarginatus range but still below that of Lasius productus. Paramere similar in proportionate size and shape to that of alienus.

Specimen no. 2. Mandible partly decomposed and further obscured by a fissure, apparently with a well-developed spical cleft and basal angle. Size somewhat smaller than no. 1. Paramere similar in proportionate size and shape to that of Lasius alienus.

Specimen no. 3. Subapical cleft present but set about one-third back from the apex, an intermediate sitkaensis-niger condition occasionally seen in flavus and rarely in alienus. Basal angle weakly developed, close to niger type. HW ca. 0.66 mm.

Type Material
Wilson (1955) - SYNTYPES. The only specimens designated as types by Mayr were several males inclosed in a single piece of amber in the Menge Collection (Leipzig). These were given as the source of his male diagnosis ("Typen bei der Diagnose") and described as having denticulate mandibles.