Agapetus iridis Ross

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 : 24-25

Agapetus iridis Ross

Fig.15a, 15b, 15c . Map 15

Agapetus iridis Ross 1944: 269

Type locality, “small creek near Tahawus, Adirondack State Park, Essex Co., NY.” ( INHS)

Diagnosis. The very elongate inferior appendages (length> 4.5 times depth) separate A. iridis from all North American Agapetus except A. baueri , A. flinti , A. jocassee , and A. pinatus . Differs from A. baueri and A. jocassee in having 3 denticles per inferior appendage (versus only 2). Differs from A. pinatus in having the lateral (ventral) denticle of X extending farther posteriad than the median (dorsal) denticle and in having the lateral denticles with more points (1-4 per denticle, visible at 50 diameters magnification) than the median denticle (usually with a single point, rarely with 2 points); in A. pinatus median denticle extends farther posteriad than lateral denticle, and median pair of denticles on X each with more points (2 or more) than lateral denticles (typically 1 point). In addition, non-terminal denticles on inferior appendage of A. iridis are widely spaced, at 0.5 and 0.8 times length of appendage, versus one dorsal to the other, both at about 2/3 length of appendage in A. pinatus ; dorsal setae on preanal appendage of A. iridis are present only on the distal 3/4, but present along the entire exposed dorsal margin in A. pinatus . Most similar to A. flinti , from which it differs in having the middle denticle on the inferior appendage near the dorsal margin and the basal denticle on the ventral margin (both non-terminal denticles near mid-depth in A. flinti ; also, in A. iridis the tip of the inferior appendage is truncate versus smoothly rounded in A. flinti ).

Description. Male. Length 5.4-6.2 mm (n = 11). Male genitalia: Lateral view ( Fig. 15a ), anterior margin of IX slopes down and forward at 45 o to midline, then smoothly down and back at 50 o angle to ventral margin; dorsal margin short, 1/4 length of ventral margin; posteriodorsal shoulder of IX prominent, its dorsal margin horizontal, 1/4 length of IX, rounded at posterior corner, concealing basal fifth of preanal appendage; posterior margin convex, sloping (80 o) down and back to midline, then down and forward (70 o) to lower margin of inferior appendage. Ventral margin of IX convex, with transverse groove near anterior margin. Preanal appendage linear, occasionally expanded toward pointed tip, 1/2 length of inferior appendage, length = 7 times depth, 7-17 setae dorsally along distal 3/4. Segment X sclerotized only on ventral margin, sclerotized portion thickest on basal 1/3 (= preanal appendage depth), distal 2/3 forms 160 o angle with basal 1/3; length of X subequal to that of inferior appendage; pointed denticle at tip of X horizontal to slightly angled dorsad; a second dark denticle, usually with a single point, straight to decurved, dorsal to other denticle. Inferior appendage length = 5.5 times depth at middle, dorsal and ventral margins nearly parallel. Dorsal margin sinuate, decurved at truncate tip; darkened terminal posterioventral denticle on inner face visible as a dark dot. An additional denticle on inner margin may be visible as a dark, oblique line at mid-length near ventral margin; a third inner denticle appears as a dark dot midway between these denticles, near dorsal margin.

Dorsal view ( Fig. 15b ). Anterior margin of IX deeply concave; posterior margin not apparent except laterad, projected mid-dorsal length subequal to width of preanal appendages. Preanal appendages with concave outer margin, convex inner margin, tip varying from pointed to expanded and rounded; inner base with triangular expansion extending toward midline of IX. Sclerotized arms of X with basal 1/3 convergent, meeting on midline at 65 o angle from each other, then divergent at 20 o angle to bases of dorsal denticles, then more divergent to tips of ventral denticles. Ventral denticles divergent from body axis at 60-90 o, dorsal denticles less divergent; ventral denticles with tips often bifid or trifid. Segment X membranous dorsally from bases of dorsal denticles nearly to posterior margin of IX, sides (not shown) convergent from posterior margin to truncate anterior margin. Inferior appendages (not shown) with outer margin nearly straight, incurved at or near tip, all three pairs of denticles apparent.

Ventral view ( Fig. 15c ). Anterior margin of IX concave, posterior margin forms obtuse angle (110 o) between inferior appendage bases; triangular area between outer bases of inferior appendages depigmented; a transverse row of setae at anterior margin of depigmented area. Inferior appendages slightly swollen at base, then straight or slightly convex to rounded tips; inner margin concave from base to broad median denticle, which varies from rounded or truncate and not black to sharply pointed and black, on narrow shelf on ventral edge, then equally concave from this denticle to terminal denticle; third pair of denticles visible, subequal to terminal denticles, and closer to median denticles than to terminal denticles.

Larva. All sclerotized areas straw yellow, except brown in areas typically dark for genus. Some larvae with only a transverse arc of 4 faint muscle scars on middle of frontoclypeus; well marked larvae with 9-10 muscle scars on middle 2/3 of frontoclypeus, 6-7 on genae on each side of vertex, in 3 rows (2-3 per row) behind eye, and with 3-4 on each side on posterior portion of pronotum.

Emergence dates. 20 April-13 August.

Distribution. AL Calhoun, Clay (2), Cleburne (3), Tallapoosa. CT Fairfield. MA Franklin (2), Hampshire. NC Buncombe, Caldwell (5), Jackson, Macon, McDowell (5), Moore, Swain (6), Transylvania (2). NH Coos (2), Grafton (2), Strafford (2). NY Essex (3), Hamilton. PA Monroe. PQ Brome. SC Cherokee, Pickens (2). TN Carter (5), Polk. VA Bath(2), Carroll, Washington.

Figures

Figure 13-15. Agapetus spp. male genitalia. 13) Agapetus ibis Etnier, Baxter, and Parker. 13a, lateral view; 13b, dorsal view; 13c, ventral view of IX and inferior appendages. 14) Agapetus illini Ross. 14a, lateral view; 14b, dorsal view; 14c, ventral view of IX and inferior appendages. 15 Agapetus iridis Ross. 15a, lateral view; 15b, dorsal view; 15c, ventral view of IX and inferior appendages.