Agapetus spinosus Etnier and Way

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 : 38-39

Agapetus spinosus Etnier and Way

Fig. 24a, 24b, 24c . Map 24

Agapetus spinosus Etnier and Way 1973: 425

Type locality, University of Tennessee Plateau Experiment Station, 6 rd mi w of Crossville, US 70, Cumberland Co., TN. ( NMNH)

Diagnosis. Similar to A. hessi , A. kirchneri , and A. walkeri in having ventral arms of X slender, outcurved at tip, and terminating in one to several denticles. Differs from A. kirchneri in lacking a ventral row of denticles on inferior appendage, and in having the terminal denticle ventral to mid-depth (inferior appendage with ventral row of denticles, terminal denticles dorsal and ventral in A. kirchneri ). Most similar to A. hessi and A. walkeri , differing from both in having about 5 slender denticles at tip of each ventral arm of X (versus 1 or 2). Further differing from A. hessi in having a single denticle at tip of inferior appendage (2 in A. hessi ). Further differing from A. walkeri in usually lacking a prominent subbasal denticle laterally on each arm of X.

Description. Male. Length 5.5-6.6 mm (n = 7). Male genitalia: Lateral view ( Fig. 24a ), anterior margin of IX slopes down and forward to midline at 45 o, then down and back at 30-40 o to convex ventral margin, ventral 1/8 more vertical; dorsal margin straight, slightly longer than depth of preanal appendage, 1/4 length of ventral margin, down-sloped, forming obtuse angle with up-sloped dorsal base of X; posterior margin slopes gently down and back, covering basal 1/3 of preanal appendage, then vertical, straight to convex, to near ventral margin; ventral margin 1/2 length of inferior appendage. Preanal appendage rod- shaped, length = 6 times depth, tip rounded, truncate, or pointed; length = 1/2 that of inferior appendage, dorsally with10-15 erect setae on entire exposed area. Dorsal margin of X sloping upward, slightly sclerotized basally, distally membranous except for ventral arms. Ventral arms slender, ventral margin straight on basal 1/3, forming obtuse angle with distal portion which is also straight, then curved upward near tip to darkened terminal denticles. Inferior appendage length = 2 times depth, equal to X. End of inferior appendage with dark spot below mid-depth representing terminal denticle, upper and lower corners rounded. In ventrolateral view distal third of ventral margin swollen, and a horizontal carina conspicuous on ventral 1/2 of outer margin of inferior appendage from base to 3/4 length.

Dorsal view ( Fig.24b ). Anterior margin of IX concave. Preanal appendages divergent from body axis at 30 o, inner margin convex, sides parallel. Dorsal, sclerotized portion of X not apparent; ventral arms converge to contact at mid-length, then parallel or slightly divergent to near tips, which curve abruptly through 60-90 o, tips darkened, each with about 5 slender, sharp denticles; a small pair of lateral denticles occasionally present near base (not shown). Darkened, in-turned denticle at end of each inferior appendage triangular.

Ventral view ( Fig. 24c ). Anterior and posterior margin of IX broadly concave, posterior margin apparently not projecting between inferior appendage bases, triangular area between posterior end of IX and bases of inferior appendages apparently membranous and depigmented, a transverse row of setae at anterior base of depigmented area. Inferior appendages with outer margins nearly straight, parallel to slightly convergent, tips rounded, dorsal tips flared out from lateral carina in slightly oblique views; terminal denticle transverse to directed slightly posteriad; inner margins in contact at base, divergent from each other at 75 o on basal 1/8; sinuous but essentially parallel to distal 1/8 where divergent from each other at 90 o and concave to base of terminal denticle.

Larva. Sclerites straw-yellow, with brown darker markings typical for genus. Very similar to the larva of A. walkeri , with the following characters possibly offering separation. In A. spinosus , muscle scars on the frontoclypeus are conspicuous only on the posterior 1/2, with an anterior transverse pair at the level of the marginal concavity and another pair just anterior to the lateral angles, all of these midway between the lateral margin and the midline; an additional pair of dark muscle scars occurs near the lateral margin, just posterior to the lateral angles; a cluster of 3 similar scars forms a triangle, “point” forward, near the posterior end of the sclerite. There are marginal dark areas at the lateral concavity just anterior to mid-length and at the lateral angles. Muscle scars on the pronotum are similar in size and color to those on the head, and confined to the posterior third. Metanotal sclerites are darker than adjacent membranes, as dark as the darkened posteriolateral corners of the mesonotal sclerites. In A. walkeri , muscle scars on anterior 1/2 of frontoclypeus are nearly as prominent as those on posterior 1/2, and the darkened area marginally at mid-length is absent.

Emergence dates. 3 May-early June.

Distribution. AL DeKalb, Jackson (2). TN Bledsoe, Cumberland (6), DeKalb (2), Franklin, Grundy, Roane, Scott.

Discussion. Taken with A. crasmus . This species appears to have a high fidelity to the Cumberland Plateau physiographic province.

Etymology. Not given in original description, but spinosus is in reference to the numerous denticles at the termination of the ventral arms of X.

Figures

Figure 22-24. Agapetus spp. male genitalia. 22) Agapetus pinatus Ross. 22a, lateral view; 22b, dorsal view; inferior appendages not shown; 22c, ventral view of IX and inferior appendages. 23) Agapetus ruiteri Parker, Etnier, and Baxter. 23a, lateral view; 23b, dorsal view; 23c, ventral view of IX and inferior appendages. 24). Agapetus spinosusEtnier and Way. 24a, lateralview; 24b, dorsal view; 24c, ventral view of IX and inferior appendages.