Laccophilus horni Branden 1885

Laccophilus horni Van den Branden (Figs. 209-216, 324)
Laccophilus lateralis Horn, 1883, p. 282. Lectotype, male, Academy of Natural Sciences, Philadelphia, No. 2961, Arizona.
Laccophilus horni Van den Branden, 1885, p. 21; Leng, 1920, p. 76; Zimmermann, 1920, p. 19.
DIAGNOSIS. — Elytral pattern, pronotal markings, and absence of metacoxal file separate this species from all other ones in North America. Only pictus and leechi have an elytral pattern with yellow spots on a black or nearly black background. L. pictus has a file and darkened epipleura. The epipleura are pale in horni, and the arrangement of the spots is different (figs. 300-304, 324). L. horni and L. leechi have very similar elytral patterns and lack files, but the pronotal markings of leechi are more extensive. Also, horni has a mean length of about 4.5 mm; and leechi is only about 3.5 mm long.
DESCRIPTION. — Medium (length, 4.10 to 4.95 mm; width, 2.45 to 3.10 mm), dark brown or black species with yellow spots; metacoxal file absent, prosternal process short; sawlike ovipositor. COLOR. Head: pale brownishyellow faintly tinged with red except for dark reddish-brown occiput between the eyes; appendages pale. Pronotum: pale brownish-yellow tinged with red in center and laterally, but with dark reddish-brown bilobed spots on front between the eyes and at the apex; entire posterior margin translucent brownish-red. Elytra: strongly marked spotted pattern of yellow and very dark reddish-brown or black; epipleura pale anteriorly, posterior half may darken to reddish-brown. Tergite VIII: pale yellow-brown. Venter: medium yellowish-brown; proand mesolegs generally paler, darker at the bases of mesocoxae and on the metacoxal plates around the base of the hind legs; lateral margins of plates also dark reddish-brown. Genitalia: variably pale reddish yellow-brown to reddish-brown. ANATOMY. Microreticulation: double on head, pronotum, and elytra; surface shining. Head: supraclypeal seam arching slightly above the clypeal margin. Pronotum: relatively short since angle between it and the elytra approaches 180 degrees; WH/PW, 0.69; LP/PW, 0.38; surface roughened, but shiny. Elytra: apical truncation barely perceptible; females without epipleural flange. Venter: prosternal process short, slender, with well-defined crest; postcoxal processes not laterally projecting past the midline, but instead forming a nearly straight line or bending slightly more anteriorly than the midline; last abdominal segments of both sexes not truncated, but perhaps somewhat elongated to subtriangular; deep, marginal groove extending almost the entire lateral posterior margin to the crest in females and about half the length of the margin on either side of the apex in males; median crest nearly symmetrical in both sexes; numerous setigerous punctures scattered over the surface, thickest on crest. Legs: male proand mesotarsi enlarged slightly in a dorsoventral plane; fifth tarsal segments on both pair of front legs one and three-quarters to twice as long as corresponding fourth; mesofemoral setae (8 to 9) much larger than profemoral ones (7) ; metatibial spur nearly as long as two tarsal segments. Genitalia: oval plate with produced acuminate point; its median crest only distinctly raised near apex, but apparent anteriorly with a bend to the right; a few weak raised lines on either side; aedeagus simple and tapering gradually along entire length; right paramere with blunt apex; ovipositor with about 14 sawlike teeth.
NOMENCLATURAL NOTES. — Horn ( 1883 ) used a preoccupied name in describing this species, and this was corrected by Van denBranden (1884).
VARIATION. — Although the yellow elytral spots vary in size, there is no particular geographic trend. The subbasal spots may be completely joined or separated into two or three discreet ones.
Females tend to be slightly larger than males. The peak frequency for females lies at about 4.6 mm and that for males at about 4.5 mm (fig. 25). In a total of 254 specimens measured, however, duplex Earzi wmmzMZL
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gentilis gentilis TOTAL LENGTH (mm) duplex, and L. undatus. Males shown in Crosshatch; females, stippled. the largest individual was a male that was about 5.0 mm long. There may be some geographical variation in the size of females compared to males. In two samples (Table 19) from Arizona and Sonora, there is a fairly good separation of the means of females and males. The mean length of females over males in the Arizona sample is highly significant, but from Jalisco south, there is no difference. Sonoran region populations are longer, but with the large gap in samples, it cannot be determined if the difference is racial, clinal, or local. — The distribution as now known of Laccophilus horni is separated into four areas (fig. 23). One is in southeastern Arizona and northeastern Sonora, another in the Davis Mountains in Texas, the third in San Luis Potosi, and the last in a fairly continuous chain from Nayarit to Oaxaca. Some of the separation appears to be due to a lack of collecting. It seems likely that there should be populations almost continuously from the one in northeastern Sonora to Nayarit. On the other hand, the Davis Mountain population may be truly allopatric to any other populations. There is a little suitable habitat between it and populations to the west or south. The San Luis Potosi localities are close enough to those in Michoacan to suspect that they are not truly allopatric populations.
L. horni has a high fidelity for stream pools occurring in oak woodland. In all parts of its range it is found near oak in hilly terrain. It can be collected anywhere between 1000 and 5000 feet in streams or pools that have granitic gravelly bottom. It prefers to stay in extremely shallow water (3 inches or less), darting from one pebble to the next. The easiest way to collect this species is to strain some gravel with the rim of a metal sieve just above the water surface and allow the specimens to swim upward where they can be picked up with a forceps. They are probably one of the more difficult species to collect in large numbers, which probably explains why they are seldom abundant in collections. UNITED STATES OF AMERICA. — ARIZONA. Cochise County. Chiracahua Mtns., 1, v.9.— , Hubbard & Schwarz (USNM); H. Martyr L, 2 5,2 9, ix.5.61, JRZ (NMSU); Portal, 1 6, viii.— .58, P. Opler (BERK); SWRS, 1, vii.4.56, O. L. Cartwright (USNM); 1 S, 19, vii. 22.56, E. Ordway; 1 9, vii. 19.57, M. Stathen (AMNH); Cave Ck. Cn.. 1 9, ix.13-14. — , B. Malkin TOTAL LENGTH (mm) Crosshatch; females, stippled.
(FM). Huachuca Mtns., Bear Canyon, 1, v.8.53, A. & H. Dietrich (CNL). Gila County. Pinal Mtns., 1, iv.— .— , D. K. Duncan (CNL); 1, vi.15.47, F. H. Parker (CAS). Graham County. Graham Mtn., Marijilda Canyon, 11 S, 16 2, ix.12.52, B. Malkin & V. E. Thatcher (FM). Pima County. Baboquivari, 2, —.—.24, C. C. Poling (CNL); 7, ix.24.33, Bryant (CAS). Catalina Mtns., 2, iv.18-v.16. — , Hubbard & Schwarz (USNM); Sabino Canyon, 2, vii. 11.49, D. J. & J. N. Knull (USNM); 1 5, ix.6.63, V. L. Vesterby (DAV); 25, xii.28.50, R. S. Beal (BERK); Molino Basin, 3, vi.11.58 (CAS); 1 S, vi.9.54, R. S. Beal (NMSU); 3 $, 2 2, vi.9.54, R. S. Beal (BERK); 1 2, xi.27.27, F. H. Parker; 1 2, x. 16.43, J. Hendrickson (ARI). Santa Cruz County. Nogales, 2, iv. — .97, Koebele (CAS). Pena Blanca, Pajarito Mtns., 4 8, 3 2, vii. 26. 64, R. H. Arnett & E. Van Tassel (CUA). Santa Rita Mountains, 1 2, xi.6.24, A. A. Nichol (MCHS); Madera Canyon, 1 2, x.2.63, V. L. Vesterby (DAV); 4, vii.26.55, F. X. Williams (CAS); 1 2, vi.6.56, A. Menke (LACM); Florida Canyon, 3 2, viii.6.62; 1 2, ix.7.61; 2 $, 12, xii.2.61, JRZ (NMSU). Tumacacori Mtns., 12 <5 , 6 2, vii.27.65, H. B. Leech (CAS). TEXAS. Davis County. Davis Mtns., Madero Canyon, 1, vi.14.16, F. M. Gaige (USNM) ; Phantom L., 2, viii.20.16, F. M. Gaige (CAS). County, 4 S, 4 2, viii.10.16 (MCHS).
MEXICO. — JALISCO. Mazamitla, 17 m. S., 12, xii.5.48, H. B. Leech (CAS). Between Autlan and Union de Tula, R. San Pedro, 3 <S , 7 2 , iii.28.64, JRZ (NMSU). MEXICO. Tonatico, 5 c?, 2 9, viii.29.62, JRZ (NMSU). MICHOACAN. Tzitzio, 3 9, vii.27.62; 3 m. S., 17 6, 15 9, viii.22.63, JRZ (NMSU). Uruapan, 10 m. S., 1 c?,l 9 , iii.26.64, JRZ (NMSU). MORELOS. Cuerna (vaca?), 1 9, v.—. — , Barrett (CAS). NAYARIT. Sierra de Zapotan, 2 9, xi.— .42, Eugenio Paredes (CAS). Tepee, 25 m. SE., 4 5,2 9, xi.23.48, H. B. Leech; 25 km. S, U, 1 S, ix.24.53, B. Malkin (CAS). OAXACA. EI Tule, 1 6, ix.6.64; Huajuapan, 2 km. S., 4 i , 4 9 , ix.4.64; 17 km. NE.,
1 9, ix.3.64; Oaxaca, 3 m. S., 19, viii.26.63, JRZ (NMSU). SAN LUIS POTOSI. Cuidad del Maiz, 14-15 m. E., 1 $, 2 5, ix. 19.48; San Luis Potosi,
2 m. S., 2 6, xi. 21.48, H. B. Leech (CAS). SONORA. Huachineura, 113, 7 9, vii.25.63, JRZ (NMSU).

Laccophilus horni is a species of predaceous diving beetle in the family Dytiscidae. It is found in North America and the Neotropics.