Macrelmis shepardi, 2021

Barr, Cheryl B., 2021, Revision of Macrelmis Motschulsky, 1860 in the Southwestern United States and Northern Mexico with Description of Four New Species (Coleoptera: Elmidae: Elminae), The Coleopterists Bulletin 75 (1), pp. 93-120 : 112-116

Macrelmis texana ( Schaeffer, 1911) ( Figs. 1, 19–20)

The common Texas species M. texana was described by Schaeffer (1911) as Elsianus texanus from a unique female specimen (H. P. Brown, unpublished data) from the Devils River, Texas. The male genitalia of the species are described and illustrated herein for the first time ( Figs. 20a–b). There are verified records of the species from central Texas from the following counties: Bandera, Bell, Bexar, Comal, Edwards, Gonzales, Hays, Kerr, Kimble, Kinney, Menard, Real, San Saba, Terrell, Travis, Uvalde, and Val Verde (type locality: Devils River), and it likely occurs throughout the Edwards Plateau. Specimens determined by Brown from the bordering Mexican states of Coahuila and Nuevo Leon are housed in the OMNH Recent Invertebrates Collection with the records appearing in their Recent Invertebrates Database. The New Mexico and Jeff Davis County, Texas, records attributed to M. texana by Brown (1971, 1972) are actually of M. shepardi , so the species is currently known only from Texas and Mexico. Macrelmis texana often occurs with M. texangusta in the same rivers and streams, and also has been collected with M. shoemakei in San Felipe Creek, Val Verde County, Texas.

Diagnosis. Macrelmis texana ( Figs. 19a–b) and M. texangusta ( Figs. 9a–b) occur together in some streams and historically have been confused with each other. Although the species are of similar length (4.0– 4.8 mm long and 3.8–4.8 mm long, respectively), M. texangusta is proportionally more slender than M. texana , about 3× as long as wide in comparison to 2.5×, respectively, and M. texana is more coarsely granulate. The following species are usually distinguishable from M. texana on the basis of size: Macrelmis shepardi ( Figs. 6a–c) is larger, 5.0– 5.9 mm long; M. moesta ( Figs. 15a–b) and M. shoemakei ( Figs. 17a–b) are both smaller, less

20) Male genitalia, a) Dorsal view, b) Lateral view.

than 4 mm long. Macrelmis texana ( Figs. 19a–b) is most similar to M. harleyi ( Figs. 3a–b) (4.2–5.2 mm long) and may be difficult to separate on the basis of external morphology alone, although the scutellar shield of the former is noticeably more protuberant. Fortunately, the unique male genitalia ( Figs. 20a–b), with a wide penis subparallel at the apical 1/3 and with a broadly rounded tip, serve to easily distinguish M. texana from the males of other species.

Description. Male genitalia: Elongate, about 3.5× as long as wide; well sclerotized ( Figs. 20a–b). Phallobase much longer than parameres; parameres much shorter than penis. In dorsal view ( Fig. 20a), parameres with lateral margins weakly arcuate, inner margins sinuate, apices narrowly rounded to acute; penis wide with lateral margins subparallel at basal 2/3, narrower and subparallel at apical 1/3, apex broadly rounded; penis at base wider than paramere base, at apical 1/3 much wider than paramere apical 1/3. In lateral view ( Fig. 20b), phallobase ventral margin strongly arcuate; paramere ventral margin strongly sinuate, wide at basal 2/3, slightly curved ventrally and digitate at apical 1/ 4, apex narrowly rounded; penis with apical 1/3–1/2 dorsoventrally flattened, slightly angled ventrally, apex sharply acute.

KEY TO THE DESCRIBED SPECIES OF MACRELMIS OF THE UNITED STATES AND MEXICO BASED ON MALE GENITALIA [partly modified from Hinton (1940) and H. P. Brown (unpublished data)]

1. Pronotum with a basal gibbosity anterior to the scutellum ..................................... 2

1 ʹ. Pronotum without a basal gibbosity………3

2. Length over 4 mm; prosternal process with apex acute ( Fig. 25, male genitalia); central Mexico............... M. scutellaris (Hinton)

2 ʹ. Length 4 mm or less; prosternal process with apex broadly rounded ( Fig. 22, male genitalia); central Mexico............................. ............................. M. graniger (Sharp)

3. Hind tarsi of males with tufts of long setae on ventral apices of tarsomeres 1–4 ( Fig. 6c).. ....................................................... 4

3 ʹ. Hind tarsi of males without tufts of long setae on ventral apices of tarsomeres 1–4………6

4. Male genitalia with penis not extending beyond apices of parameres ( Fig. 24); central Mexico.............. M. sandersoni (Hinton)

4 ʹ. Male genitalia with penis extending beyond apices of parameres ............................. 5

5. Size larger, 5.0 mm long × 2.0 mm wide or more; male genitalia with paramere apices rounded and curved inward ( Fig. 7a); Texas, New Mexico, Arizona, Durango .............. ............... M. shepardi Barr , new species

5 ʹ. Size smaller, 4.5 mm long × 1.9 mm wide or less; parameres with apices subacute and not curved inward ( Fig. 27); central Mexico.... .......................... M. striatoides (Hinton)

6. Pronotum without sublateral carinae………7

6 ʹ. Pronotum with sublateral carinae ........... 8

7. Male genitalia with parameres having outer margins rounded, apices abruptly curved inward; each nearly as wide as penis apex ( Fig. 23); southern Mexico, Guatemala, Honduras............................................ ..... M. leonilae Spangler and Santiago F.

7 ʹ. Male genitalia with parameres nearly parallel-sided, apices slightly curved inward; each narrower than penis apex ( Fig. 13a); Baja California Sur, Sonora .................... .............. M. mexicana Barr , new species

8. Size larger, more than 5.5 mm long ( Fig. 21, male genitalia); central Mexico................ ............................. M. grandis (Hinton)

8 ʹ. Size smaller, less than 5.5 mm long………9

9. Male genitalia with penis extending well beyond apices of parameres ................ 10

9 ʹ. Male genitalia with penis not extending much, if at all, beyond apices of parameres ............................................. 13

10. Male genitalia with penis narrowly spatulate, widened at apex ( Fig. 18a); Texas, Coahuila .................. M. shoemakei (Brown)

10 ʹ. Male genitalia not as above ................. 11

11. Body elongate and slender; male genitalia with penis tapered at apical third, apex narrowly rounded ( Fig. 10a); Texas .............. ............ M. texangusta Barr , new species

11 ʹ. Body not elongate and slender; male genitalia with penis nearly parallel-sided at apical third, apex blunt and broadly rounded ............. 12

12. Pronotum with sublateral carinae prominent; male genitalia with penis broad, abruptly constricted at apical third, paramere tip digitate in lateral view ( Fig. 20b); Texas, Coahuila .................... M. texana (Schaeffer)

12 ʹ. Pronotum with sublateral carinae low, narrow; male genitalia with penis gradually narrowed at apical third, paramere tip blunt, not digitate in lateral view ( Fig. 13); Baja California Sur, Sonora ........................... .............. M. mexicana Barr , new species

13. Male genitalia with parameres broader than penis and about the same length, paramere tips digitate and strongly curved in lateral view ( Fig. 4); body size usually larger, 4.5 mm long × 1.8 m wide or more; Arizona .......... M. harleyi Barr , new species

13 ʹ. Male genitalia with parameres narrower, slightly shorter than penis, paramere tips not digitate or strongly curved in lateral view; body size usually smaller, 4.5 mm long × 1.8 mm wide or less .......................... 14

14. Male genitalia with penis bulbous at base, wider than paramere base; penis apex broad, much wider than paramere apex ( Fig. 16a); Arizona ..................... M. moesta (Horn)

14 ʹ. Male genitalia with components slender; penis base subparallel, not bulbous, not wider than paramere base; penis apex narrow, as wide as paramere apex or not much wider ( Fig. 26); central Mexico........................ ................................ M. striata (Sharp)