Cerodontha (Dizygomyza) luctuosa Meigen

Cerodontha (Dizygomyza) luctuosa (Meigen)

(Figs. 8–12)

Description. Head including antenna, brown, gena, lunule and inner margin of orbit paler, yellowish. Thorax uniformly brown, only anepisternum narrowly yellow on dorsal and posterior margins; calypter including margin and fringe yellow. Halter white. Legs completely brown, except foreknee yellow. Abdomen with anterior tergites yellow laterally, brown medially.

Frons width 0.40–0.45 mm; ratio of frons width to eye width 2.0–2.2; orbit broad: 0.2– 0.25 width of frons at midpoint; frons slightly projecting above and in front of eye in profile, orbit forming only narrow ring below eye; eye bare; lunule with patch of silvery pubescence between antennae best seen in posterodorsal view; frons with microtomentum; 2 inclinate ori and 2 reclinate ors, anterior ori only slightly shorter than posterior ori; anterior ors 0.75–0.80 length of posterior ors; 4–5 upright or reclinate orbital setulae, normal size, in one row, present anteriorly up to level of anterior ors; first flagellomere enlarged in male, covered with white pubescence; arista as long or shorter than eye height; arista with distinct pubescence and swollen basally for 40% of its length; gena slightly deeper at rear; gena height 0.20 times eye height at midpoint; lunule broad, in form of a semicircle, or a little higher; bases of antennae widely separated. Three postsutural dc, and 1 presutural dc decreasing in size: first (posterior) dc approximately twice the size of fourth (anterior) dc; acrostichals irregular, in about 4–5 rows; prsc absent. Midtibia with moderately strong apico­ventral bristle, about 0.3 length of first tarsomere. Wing length 2.7–2.8 mm in males; M1+2 ending closer to wing tip than R4+5; costa extending to M1+2; second costal sector 4.5 times length of fourth; last section of CuA1 equal or slightly longer than penultimate. Cross­vein r­m located at 0.5–0.6 the length of cell dm. Abdomen with stridulatory mechanism present in male (a line of scales along the center of the membrane connecting the abdominal tergites and sternites).

Male genitalia. Distiphallus with tubules diverging in ventral view (Fig. 8), curving ventrally at apex in lateral view (Fig. 9). Surstylus with two stout anterodorsal, medially directed spines and 4–5 smaller ventral, medially directed spines (Fig. 10). Anal projection of epandrium small (Fig. 11).

Comments. This Holarctic species was previously known in the Nearctic region from the following localities: California, Colorado, New York, Oregon, Washington, Alaska, Northwest Territories (Spencer and Steyskal 1986; Spencer 1969). New localities include Texas (USA: Texas, Davis Mts. State Park, 30°35’04”N; 103°55’19”W, 29–30.v.2001, Malaise trap, G.A. Dahlem, 1 male, LEM) and Chiapas, Mexico (MEXICO: Chiapas, San Cristobal 7000’, 10.v.1969, H.J. Teskey, 1 male, CNC). It could be expected that this species may be more widespread in the Neotropical region. Although the presence of the stridulatory organ in the male of Cerodontha (D.) luctuosa was noted by Tschirnhaus (1972), it was not mentioned in most other previous descriptions (e.g. Nowakowski 1973, Spencer 1969, 1981, Spencer and Steyskal 1986).