Key to North American Henicopidae and Anopsobiidae

The following key is based on specimens and information from the literature, incorporating (with permission) couplets from an unpublished key by Andrew A. Weaver. As discussed in the section above, the key cannot assure that a specimen that keys to a particular name is actually that species, especially if the nominal species has been reported as having a wide geographic range. It is likely that undescribed species are included in these ranges. The key does not include Buethobius translucens Williams & Hefner, 1928, since insufficient data are available on its characters and no specimens are known to exist. This species may be a synonym of Lamyctes coeculus . The nominal North American species of Lamyctes are difficult to distinguish; they may all be synonyms of L. emarginatus, since the characters used by Chamberlin (1912, 1938, 1940) to distinguish them are a subset of the observed variation of L. emarginatus (Zapparoli & Shelley 2000) . Pending further study, these species are keyed below, as is Yobius haywardi, though it is likely actually a species of Buethobius . Zygethobius pontis comes out at two places in the key due to observed variation in the characters of the sixth tergite. Where length is used as a character it should be taken from the largest sexually mature specimens available. Colors refer to live or freshly preserved specimens. The key begins by assuming that lithobiids have been excluded by observing the presence of articular leg spurs, and the lack of the acute distal spines on the tibiae. A note for nonspecialists in centipedes: having tergites produced means that the posteriolateral corners of the tergites are drawn out into triangular projections.

1a. Coxae of legs 15 without a distal process; spiracles present or absent on first pedigerous segment; with a single ocellus.................................................................................. .. Henicopidae, Henicopinae, 2.

1b. Coxae of legs 15 with a prominent, acute, mesodistal process; without spiracles on the first pedigerous segment; ocelli lacking...................................................................................... Anopsobiidae, 13.

2a. Antennae with 21–30 articles; all tergites with rounded posterior corners; coxal pores present on coxae 12–15; tarsi of only legs 13–15 biarticulate............................................................. Henicopiini, Lamyctes, 3.

2b. Antennae with 28–43 articles; at least tergites 9, 11 and 13 produced posteriorly (with triangularly acute, projecting, posterior corners); coxal pores present on coxae 11–15; tarsi of all legs biarticulate.................. Zygethobiini, Zygethobius, 8.

3a. Antennae with 21–25 articles........................................................................... 4.

3b. Antennae with more than 26 articles...................................................................... 6.

4a. Forcipular coxosternal teeth 2 + 2................................... Lamyctes emarginatus Newport (cosmopolitan).

4b. Forcipular coxosternal teeth 3 + 3........................................................................ 5.

5a. Length 5–6 mm; head lighter color than trunk................................. Lamyctes diffusus Chamberlin (Texas) .

5b. Length 9–10 mm; head darker color than trunk......................... Lamyctes caducens Chamberlin (New Mexico).

6a. Length 5–6.5 mm................................... Lamyctes tivius Chamberlin (Mississippi, Louisiana, Alabama).

6b. Length 7.5–9.5 mm................................................................................... 7.

7a. Greatest thickness of the femur of ultimate leg 1.5X that of the tibia; antennae more than 3.5X the length of the head................................................................. Lamyctes pinampus Chamberlin (Nevada, California).

7b. Greatest thickness of the femur of ultimate leg 1.33X that of the tibia; antennae less than 3.5X the length of the head............................................ Lamyctes pius Chamberlin (North Carolina, Georgia, New Jersey, Pennsylvania).

8a. Posterior angles of only tergites 9, 11 and 13 produced....................................................... 9.

8b. Posterior angles of tergites 6 and/or 7 produced, in addition to those of tergites 9, 11 and 13......................... 10.

9a. Color yellowish brown, anterior and posterior ends darker.......... Zygethobius dolichopus Chamberlin (Utah, California).

9b. Color uniform reddish brown...................................... Zygethobius sokarienus Chamberlin (California) .

10a. Posterior angles of tergites 6, 7, 9, 11 and 13 produced...................................................... 11.

10b. Posterior angles of tergites 7, 9, 11 and 13 produced........................................................ 12.

11a. Antennal articles 28–34.............................................. Zygethobius ecologus Chamberlin (Oregon) .

11b. Antennal articles 38–40................................................................................................. Zygethobius pontis Chamberlin (general in the Appalachian Mountains from New York to North Carolina).

12a. Antennal articles more than 40............................. Zygethobius columbiensis Chamberlin (British Columbia).

12b. Antennal articles 38–40................................................................................................. Zygethobius pontis Chamberlin (general in the Appalachian Mountains from New York to North Carolina).

13a. All leg tarsi biarticulate (but see notes below).................................. Yobius haywardi Chamberlin (Utah) .

13b. Only tarsi of legs 13–15, or 14 and 15 biarticulate.......................................................... 14.

14a. Tergites 3, 5 and 8 (and sometimes 10 and 12) with posterior margin deeply embayed; 54–60 antennal articles; adult length 17– 20 mm ................................................................ Speleopsobius weaveri, n. sp. (Idaho).

14b. All tergites with straight or slightly curved posterior margins; 35–45 antennal articles; adult length less than 12 mm ..... 15.

15a. Forcipular coxosternal margins nearly smooth, without obvious teeth....... Buethobius huestoni Williams & Hefner (Ohio) .

15b. Forcipular coxosternal margins with prominent teeth........................................................ 16.

16a. Antennae with 43–45 articles; length 8–10 mm ......................... Buethobius coniugans Chamberlin (California) .

16b. Antennae with 35 or 36 articles, length 10–12 mm ......................................................... 17.

17a. Antennae less than half the length of the body; some posterior coxae with 5 pores................................................................................................... Buethobius arizonicus Chamberlin (Arizona) .

17b. Antennae more than half the length of the body; no posterior coxae with more than 4 pores............................................................................................ Buethobius oabitus Chamberlin (Mississippi) .