Eupolybothrus (Schizopolybothrus) excellens (Silvestri)

C. A. W. Jeekel, 1967, On two italian Lithobius species described by Silvestri with taxonomic notes on the genus Eupolybothrus Verhoeff (Chilopoda Lithobiidae), Beaufortia 14, pp. 165-175 : 166-169

Eupolybothrus (Schizopolybothrus) excellens (Silvestri)

Lithobius (Archilithobius) excellens Silvestri, 1894 : 580.

Lithobius (Lithobius) occultus Silvestri, 1894 : 579.

Type material. - The type material of excellens consists of a single female specimen labelled " La Spezia , Caverna del Ginepro , 1869, Abdul Kerim ". As there is no evidence in Silvestri’s description that he had more than one specimen, I have labelled it as holotype. The material of occultus was labelled " Grotta del Gazzo , 19.IX.1888, Barberi " and consisted also of a single female specimen. Apparently, Silvestri also had but one specimen of this species, and, consequently, I have labelled it also as holotype .

Descriptive notes. - The specimen of occultus is apparently not fully mature: the medial spur of the gonopods is distinctly smaller than the lateral one. This condition accounts for most of the differences between the two type specimens. The following notes made after the type of both species may supplement Silvestri’s descriptions.

Colour of both specimens much as in Lithobius forficatus : light castaneous.

Head as long as wide. Antennae about four fifths of the body length ( excellens ) or about two thirds of the body length ( occultus ), composed of 76 (exc., right antenna mutilated) and 73 (occ., right) and 61 (occ., left) antennomeres. 2nd antennomere two and a half times as long as the 3rd. Ocelli small.

Forcipular coxosternite without particulars.

Tergites slightly uneven, in the second half of the body with dispersed short setae. Posterior angles of T. 6 obtuse, of T. 7 about rectangular. T. 9, T. 11 and T. 13 with acutely angular projections (fig. 1).

Sternites dispersedly impresso-punctate.

Legs of the 14th and 15th pairs from the femur onwards with dense pore sieves on the medial (posterior) side only. Relative length of the pedomeres of the 15th leg (length of head = 100): P. 105 (exc.), 100 (occ.); F. 118 (exc.), 126 (occ.); Ti. 145 (exc.), 156 (occ.); Ta. 1 141 (exc.), 148 (occ.); Ta. 2 105 (exc.), 100 (occ.). Spinulation of legs, see table. Spines very long, the VPm spine of the first leg almost as long as the greatest length of the prefemur.

Female gonopods without particulars.

Taxonomic position. - Although not as large a genus as Lithobius , Eupolybothrus Verhoeff has gradually become quite rich in nominal species and subspecies. But apart from a small number of more widely distributed species, most of the described forms seem to be rather weakly defined. As in the other lithobiid genera, the species are characterized by a number of morphological features of subequal importance which occur in an almost infinite number of combinations. This, combined with an unusually high degree of individual variation, renders classification and identification of the species of Eupolybothrus extremely difficult. Moreover, the species of Eupolybothrus in particular almost always occur in thin populations and are seldomly collected in large numbers. Perhaps scantiness of material and the rather large size of the species have induced authors to overrate the taxonomic importance of particular differences which, in an absolute sense, are less conspicuous in the smaller species of Lithobius . Certainly too much importance has been attached, for instance, to the number of ocelli and antennomeres, and we may, therefore, safely assume that the future development of taxonomy in Eupolybothrus will greatly reduce the number of species and subspecies.

Attempts to divide the genus into subgenera have been made by Verhoeff only. The first, from 1907, was based on the absence or presence of triangular projections on the tergites and ran more or less parallel to a similar subdivision of Lithobius by Stuxberg. In this way the three following subgenera were recognized: Propolybothrus (tergites without projections), Allopolybothrus (projections on the 9th, 11th and 13th, or on the 11th and 13th tergites), and Eupolybothrus (projections on the 6th, 7th, 9th, 11th and 13th, or 7th, 9th, 11th and 13th tergites). Somehow this classification remained purely theoretical and was never brought into practice.

Ignoring altogether his earlier work Verhoeff much later created several new subgenera now based on the gonopods and the genital sternite of the males. Thus Schizopolybothrus (gonopods short, genital sternite deeply incised), Parapolybothrus (gonopods short, genital sternite rounded or slightly emarginate), and Mesobothrus (gonopods long, genital sternite deeply emarginate) came into existence; the nominal subgenus was characterized by long gonopods and a rounded or weakly emarginate genital sternite.

Unfortunately, the practical value of these subgenera is doubtful. Verhoeff created his later classification in connection with the description of new species, and many of the previously described species were not considered, either because their male genital characters had not been sufficiently described, or because they had been based on female specimens. Moreover, Verhoeff failed to correlate the genital characters with the more conventional characters.

For the time being it seems, therefore, that a more useful classification can be attained by making tentatively use of the characters offered by the spinulation of the legs, the projections of the tergites, the number of claws on the last pair of legs, the sexual modifications of the legs in the males, etc. In this way it is possible to set up a framework in which most of the described forms can be arranged, and which may be elaborated subsequently into a more satisfactory subgeneric classification.

In a previous paper (Jeekel, 1963) a review of the nomenclatorial status of Eupolybothrus and its subgenera was given. In the following key the subgenera are defined, and a new one is added.