Caseyidae Verhoeff, 1909

Shear, William A., 2021, Additions to the millipede family Caseyidae. II. Martenseya, a new genus of miniature, blind millipedes from California (Diplopoda, Chordeumatida Striariidea, Striarioidea, Caseyidae), Zootaxa 4984 (1), pp. 108-113 : 109-110

Family Caseyidae Verhoeff, 1909

Caseyidae Verhoeff 1909: 567 . Garner & Shelley 1989: 185 (complete references).

Underwoodiidae Verhoeff 1909: 568 . Causey 1963: 193 (synonymy with Caseyidae ).

Notes. Underwoodiidae , with only the genus Underwoodia Cook & Collins, 1895 , was synonymized with Caseyidae by Causey (1963). The synonymy was supported by Gardner & Shelley (1989). Underwoodia , with two species distributed transcontinentally in northern North America and one in the Russian Far East, is the only trans-Beringian genus in the family ( Shelley 1993). Species of Caseyidae may be distinguished from other chordeumatidan families in northwestern North America according to the key below.

The present classification of the Caseyidae is not analytical, without subfamilial or tribal taxa established. Gardner and Shelley (1989) had little to say about the possible relationships of the genera, excepting that Vasingtona and Ochrogramma shared two synapomorphies in the males, a ventral lamella extending from the mandible and long gonapophyses on the second coxae. Material available to me includes at least three additional distinctive genera in addition to Martenseya n. gen. There are also many new species of Opiona , which may turn out to be the most speciose genus in the family. Until this additional diversity is described, it would be unwise to suggest any new taxa between the level of family and genus.

Species of the family are rich in characters associated with secondary sexual modifications of the males. The second legpair has processes from the coxae which Gardner and Shelley (1989) called gonapophyses, which may be long or relatively short. The third legs are often strikingly modified, with long, flattened coxae and reduced telopodites which sometimes articulate laterally near the midpoint of the extended coxae. The gonopods of most species are complex, and the terminology used by Gardner and Shelley (1989) was reevaluated by Shear and Leonard (2007). For example, the structure they called a telopodite is in fact the colpocoxite, resembling that found in the related family Striariidae : a sclerotized structrure derived from the coxal gland of the eighth leg. What they refer to as colpocoxites are in fact angiocoxites, modifications of the rims of the coxal glands. The ninth legs are reduced to a single telopodite podomere that is large and usually button-like, protruding laterally beyond the pleurotergites of the seventh ring and allowing the identification of males as such in the field. Curiously, Gardner and Shelley (1989) never described or even mentioned the highly modified coxae of the tenth legpair, simply stating that the tenth coxae are enlarged and bear an eversible gland. In fact in the species of Caseya and Opiona I have examined, the tenth coxae have an array of lobes and processes that are definitely of taxonomic value.

Key to genera of the family Caseyidae

1a. Eyes lacking; usually less than 10 mm long................................................................ 2

1b. Eyes present; usually 10 mm long or more................................................................. 3

2a. Length of mature males 3-4 mm; legpair 3 unmodified; gonopods without flagellocoxites; Marin Co., California .............................................................................................. Martenseya n. gen.

2b. Length of mature males 8-10 mm; legpair 3 with slightly elongate coxae, reduced telopodites; gonopods with flagellocoxites; caves in Calaveras Co., California ................................................................. Speyoseya

3a. Male mandibular stipes with broad, flattened ventral process; gonapophyses of legpair 2 as long or longer than telopodites; gonopods with many tiny, much branched processes......................................................... 4

3b. Male mandibular stipes unmodified; gonapophyses of legpair 2 shorter than telopodites; gonopods lacking tiny, much branched processes........................................................................................... 5

4a. Length 18-22 mm; southwestern British Columbia to northwestern Oregon ............................... Vasingtona

4b. Length less than 15 mm; northwestern Oregon to extreme northwestern California ...................... Ochrogramma

5a. Length 8-10 mm ...................................................................................… 6

5b. Length 15 mm or greater............................................................................... 7

6a. Legpair 3 coxae much elongated, with apical tuft of setae, telopodites reduced; gonopods relatively simple, consisting of two coxites, flagellocoxite absent; Washington Co., Oregon ............................................... Metopiona

6b. Legpair 3 coxae only slightly elongated, lacking apical tuft of setae, telopodites of nearly normal size; gonopods with flagellocoxites; central to northern British Columbia (but also northern Rocky Mountains from Alberta to Utah, southern Canada and northern United States from Quebec and Vermont west to North Dakota and Manitoba; Russian Far East)..... Underwoodia

7a. Legpair 3 telopodites much reduced, prefemora enlarged, flattened; legpair 7 coxae without lobes or processes; gonopod coxites with multiple flagelliform branches in addition to flagellocoxites; San Francisco Bay area to Alexander Archipelago, Alaska ........................................................................................ Opiona

7b. Legpair 3 telopodites not much reduced, prefemora not enlarged; legpair 7 coxae with lobes and/or processes; southern California (Los Angeles Co.) and Sierra Nevada to northwestern Washington .................................... Caseya