Solenopsis nitida (Dlussky & Radchenko, 1994)

Csosz, Sandor, Seifert, Bernhard, Laszlo, Mark, Yusupov, Zalimkhan M. & Herczeg, Gabor, 2023, Broadly sympatric occurrence of two thief ant species Solenopsis fugax (Latreille, 1798) and S. juliae (Arakelian, 1991) in the East European Pontic-Caspian region (Hymenoptera, Formicidae) is disclosed, ZooKeys 1187, pp. 189-222 : 189

Solenopsis nitida (Dlussky & Radchenko, 1994)

Diplorhoptrum nitidum Dlussky & Radchenko, 1994. [images of types, description]

Notes.

This taxon was described also from Armenia, some 200 km SE of the type locality of S. juliae . The type series consists of workers and gynes collected by A. Radchenko from a single nest near to the village Legvaz [38.938°N, 46.216°E], 25 June 1986. Direct examination of type specimens deposited in the museums of Kiev and Moscow was also prevented by the ongoing Russian-Ukrainian war. Instead, we evaluated the images of the holotype gyne and a paratype worker provided by www.antweb.org under the specimen identifiers CASENT 0917366 and CASENT 0917367. The evaluation suggests a synonymy of Solenopsis nitida with S. juliae based upon the following arguments. The measurements of the paratype worker derivable with an acceptable error from the images were in µm CL 557, CW 493, FL 99, FR 99, CLSPD 89, PEW 163, PPW 156, MW 293 and ML 609. Running the absolute data as wild-card in a LDA against the data pool of BS, the paratype is allocated with p = 0.9994 to the S. juliae cluster and it is allocated also to this cluster by the PCA using the data set of SC (Fig. 5 ). Furthermore, the holotype gyne shows the sculpture reduction characteristic for S. juliae but there is one problem: the gyne is, as it is the case in all the paratype gynes, much smaller than average S. juliae gynes. As there is no indication for miscalibration of the scale in the images by comparing with measurements given by Dlussky and Radchenko (1994), these small absolute body size values must be considered as real. We derived the following measurements in µm from the images of the holotype gyne: CL 659, CW 668, FL 134, FR 134, CLSPD 100, MW 528, PEH 291, PPH 280, MH 705, and ML 1301. Proposing herewith a synonymy of S. nitida with S. juliae , we consider the holotype gyne as a microgyne with allometric changes of body shape, but we also encourage a more profound investigation of the problem after extensive collections have been done in the Caucasian region.

Material examined.

Numeric phenotypical data were taken by SC in 17 samples (largely nest samples) with 62 workers. BS investigated 16 nest samples with 66 workers and 12 gynes, the latter collected either from nests or caught during nuptial flight. For details see Suppl. materials 1, 2.

Geographic range.

According to our data including the Pannonian Basin and the complete Balkans and stretching east over Asia Minor (Fig. 8 ), the whole Caucasian region to the western shores of the Caspian Sea ( Yusupov 2014).

Diagnosis.

Worker (Table 4 , Figs 16 - 19 ): Smaller than Solenopsis fugax , mean CS 460 µm. All shape ratios given below are mean values allometrically corrected for CS = 480 µm. Head less elongated than in Solenopsis fugax , CL/CW480 1.152. Hind margin of vertex in full face view both in minors and majors straight or very feebly concave. Scape slightly shorter than in Solenopsis fugax , SL/CS480 0.692. Frontal carinae short, often slightly diverging frontad, FL/CS480 0.218, FR/CS480 0.210. Preocular distance slightly smaller than in Solenopsis fugax , PrOc/CS480 0.184. Eye small, EL/CS480 0.096. Inner clypeal dents spiny and moderately long (CLSPLM/CS480 0.055), their tips often diverging and as result more distant than in Solenopsis fugax (CLSPD/CS480 0.148). Lateral clypeal dents small (CLSPLL/CS480 0.018). Frontal lobes carinulate, whole surface of vertex except for the numerous foveolae of the seta bases completely smooth and shiny. Mesosoma shorter than in Solenopsis fugax (ML/CS480 1.155), and less wide (MW/CS480 0.585), always with a moderately deep metanotal groove (MpGr/CS480 0.027). Whole mesosoma smooth and shiny except for 3-6 longitudinal carinulae on lateral metapleuron. Petiole in lateral view with a relatively short peduncle and a high node with a semicircular dorsum, the whole node slightly inclined caudad. Petiole much higher than postpetiole (PEH/CS480 0.368, PPH/CS480 0.292) but in contrast to Solenopsis fugax distinctly narrower than postpetiole (PEW/CS480 0.296, PPW/CS480 0.324). Both waist segments completely smooth and shiny. Head, mesosoma, waist, gaster, femora, tibiae, and scape with very abundant, fine and long setae. Pubescence absent. Whole body and appendages light yellowish with a brownish color component which is often more expressed than in Solenopsis fugax .

Gyne (Table 5 , Figs 20 , 21 ): Small, mean CS 798 µm. Head clearly shorter than wide, CL/CW 0.969. Inner third of hind margin of vertex in full face view weakly convex or straight. Scape short, SL/CS 0.657. Frontal carinae short, subparallel and slightly more approached than in Solenopsis fugax , FR/CS 0.240. Preocular distance small, PrOc/CS 0.125. Eye moderately large, EL/CS 0.295. Inner clypeal dents spiny and rather long (CLSPLM/CS 0.050), their tips more distant than in Solenopsis fugax (CLSPD/CS 0.162) and often slightly diverging. Lateral clypeal dents much less developed than the inner ones (CLSPLL/CS 0.012). Frontal lobes, lateral clypeus and genae carinulate, remaining head surface except for large foveolae of the seta bases completely smooth and shiny, as clearest difference to Solenopsis fugax in particular central vertex without any carinulae or rugulae (compare Figs 11 , 13 , 18 ). Mesosoma long (ML/CS 1.991) and much higher than wide (MH/CS 1.248, MW/CS 1.016). Whole mesosoma smooth with exception of carinulate lateral scutum and whole metapleuron and anepisternite. Petiole in lateral view with a short peduncle, a high node which is slightly more inclined caudad than in Solenopsis fugax ; petiole as high as postpetiole (PEH/CS 0.476, PPH/CS 0.470); dorsal crest of petiole node in dorsal view much wider than long, the petiole in contrast to Solenopsis fugax much narrower than postpetiole (PEW/CS 0.421, PPW/CS 0.496). Dorsum of both waist segments nearly smooth, the lateral surfaces slightly carinulate. Head, mesosoma, waist, gaster, femora, tibiae, and scape with very abundant, fine and long setae. Pubescence absent. Usually dark to medium brown; legs, antennae and mandibles yellowish.

Figures

Figure 5. Principal component analyses of residuals of Solenopsis worker morphometric data. Each small dot represents a colony sample. Large dots represent centroids. Double rings represent type specimens or type series. Note: four workers mounted on two different pins (3 and 1 workers respectively) of the S. cypridis syntype material appear separately in the plot as red circles.

Figure 8. Geographic map shows the distribution of the samples analyzed in this study. Blue dots: S. juliae, ocher dots: S. fugax, black dots: S. cypridis.

Figure 11. Head of minor worker of Solenopsis fugax in full-face view.

Figure 13. Head of a macrogyne of Solenopsis fugax in full-face view.

Figure 16. Head of major worker of Solenopsis juliae in full-face view.

Figure 18. Head of minor worker of Solenopsis juliae in full-face view.

Figure 19. Lateral view of Solenopsis juliae minor worker.

Figure 20. Head of a macrogyne of Solenopsis juliae in full-face view.

Figure 21. Lateral view of a Solenopsis juliae macrogyne.