Agapetus diacanthus Edwards

Etnier, David A., Parker, Charles R., John T. Baxter, Jr., Long, Todd M. & Drive, News Sentinel, 2010, A review of the genus Agapetus Curtis (Trichoptera: Glossosomatidae) in eastern and central North America, with description of 12 new species, Insecta Mundi 2010 (149), pp. 1-77 : 13-14

Agapetus diacanthus Edwards

Fig. 7a, 7b, 7c . Map 7

Agapetus diacanthus Edwards 1956a: 4

Type locality, 1.5 mi nw of Dunlap on TN 108, Sequatchie Co., TN (but see discussion). ( NMNH)

Diagnosis. The inferior appendage, lateral view, forms a nearly perfect rhombus only in this species and in A. crasmus . Details of the ventral arm of segment X are very different in the two species—in A. diacanthus the two denticles are terminal and separated by a vertical concavity (versus denticles dorsal, at same level, and separated by a horizontal concavity in A. crasmus ). In addition, in A. diacanthus the internal darkened ridge along posterior margin of inferior appendage has only two denticles, one at each end of the ridge; in A. crasmus there is a third denticle about midway on this ridge.

Description. Male. Length = 5.5-5.7 mm (n = 2). Male genitalia: Lateral view ( Fig. 7a ), anterior margin of IX slopes down and forward, slightly concave, at 60 o angle to middle of segment, then slopes down and back at 75 o, slightly convex, to convex ventral margin; dorsal margin straight, sloping down and back at 10 o, 3/4 length of ventral margin; posterior margin slopes down and back at 75 o to midline, then angled down and forward at 75 o to ventral margin; both dorsal and ventral halves of posterior margin straight. Preanal appendages 1/2 length of X, length = 3 times depth, with dorsal and ventral margins parallel, posterior edge symmetrically rounded, about 15 setae dorsally on entire exposed length. Segment X lateral areas sclerotized throughout, more heavily so on ventral arm; ventral arm terminating distally in darkened denticle that is a smooth continuation of ventral margin. Ventral arm narrowest at base, gradually widening to base of nearly vertical, concave posterior portion of X which terminates dorsally in a darkened denticle. Inferior appendage nearly a perfect rhombus, length = 2.5 times depth, dorsal, ventral, and posterior margins slightly convex, basal margin straight, dorsal and ventral margins slightly longer than basal and posterior margins; acute angles about 45 o. Dark, internal ridge along posterior margin with denticles at each end of ridge visible as a slight swelling.

Dorsal view ( Fig. 7b ). Anterior margin of IX deeply concave, posterior margin truncate, weakly defined, mid-dorsal length = 3/4 length of preanal appendage. Preanal appendages with margins slightly sinuate, inner margin concave at base, convex distally; outer margin parallel to inner margin; tip rounded. Basal junction of dorsal inner edges of X form 60 o angle, divergent 2/3 distance to dorsal denticle, then convergent to dorsal denticle. Ventral arms converge to nearly meet slightly past mid-length and then diverge to tips. Inferior appendages (not shown in Fig. 7b ) with outer and inner edges straight, subterminal denticle transverse.

Ventral view ( Fig. 7c ). Anterior margin of IX concave, posterior margin forming 90 o angle between bases of inferior appendages; triangular area posterior to bases of inferior appendages depigmented. Outer margin of inferior appendage straight or slightly concave between bulbous base and rounded tip; basal half of inner margin straight; diverging from each other at about 60 o; distal half concave, with small basal denticle and larger, transverse denticle at each end of denticulate ridge. Ventral arms of X (not shown in Fig. 7c ) as in dorsal view but dorsal denticle not visible.

Larva. Very similar to that of A. crasmus . Potential differences are as follows. No large brown spot or spots on each side of the vertex. Frontoclypeus lacking a pale area size of dark eye spot on each side at mid-length.

Emergence dates. 7-23 June.

Distribution. TN, Marion and Sequatchie counties. Besides the type locality (see Discussion) we have records from: UT 1.387, tributary to Coops Cr. at 523 Mountain View Circle on road to Coke Ovens, off Hickory Street, Dunlap, Sequatchie Co.; UT 1.388, Hendrix Cr. at TN 28, Marion/Sequatchie Co. line; UT 1.1022, seep at 1744 TN 108, w side, 2.4 rd mi n of jct. TN 28 in Whitwell, Marion Co.; and UT 1.1025 (probable type locality), creek at TN 108 1.9 rd mi n of jct. TN 28 in Whitwell.

Discussion. Edwards (1956a) lists the type locality in reference to Dunlap, Sequatchie Co. In his l966 paper on Trichoptera of middle and west TN, he lists only one locality for A. diacanthus , presumably the type locality, as 1.5 miles nw of Travis Mills on TN 108, the same information associated with his original type locality except the place name is changed from Dunlap to Travis Mills. We find no Travis Mills near Dunlap, nor in Sequatchie Co., and TN 108 does not approach Dunlap or even enter Sequatchie Co. The only Travis Mills we could locate in Tennessee is well to the north, in Overton Co. We suspect that the actual type locality is on TN 108 1.5 mi n of Whitwell, in Marion Co. We visited this last locality (but 1.9 rd mi n of jct. TN 28 on TN 108) on 19 April 2006, and found only dead, mature pupae. We suspect these were from the previous spring, and that the stream had gone dry and remained dry until shortly before our visit. Agapetus diacanthus appears to be of very limited distribution, and may well be restricted to a small portion of the western rim of the Sequatchie Valley. It should definitely be considered for protected status. Based on larval, male, and female similarities, A. crasmus appears to be closely related.

Etymology. Not given in original description; = two-spined, probably in reference to the two denticles on the ventral arms of X or those on each inferior appendage.

Figures

Figure 7-9. Agapetus spp. male genitalia. 7) Agapetus diacanthus Edwards. 7a, lateral view; 7b, dorsal view; 7c, ventral view of IX and inferior appendages. 8) Agapetus flinti Parker, Etnier, and Baxter. 8a, lateral view; 8b, dorsal view; 8c, ventral view, segment X not shown. 9) Agapetus gelbae Ross. 9a, lateral view; 9b, dorsal view; 9c,