Agapetus minutus Sibley

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 : 31-33

Agapetus minutus Sibley

Fig. 20a, 20b, 20c . Map 20

Agapetus minutus Sibley 1926: 79

Type locality McLean, Tompkins Co., NY. (Cornell University Insect Collection)

Diagnosis. Shares the upturned, spinose posterior margin of X with A. alabamensis , A. illini , A. ruiteri , and A. tricornutus . Differs from A. alabamensis and A. tricornutus in having about 15 similar denticles, versus only 3 ( A. tricornutus ) or 5-9 ( A. alabamensis ) denticles irregular in length and spacing in these two species. Differs from A. illini in having only 1 prominent denticle on each inferior appendage (2 per appendage in A. illini ). Differs from the very similar A. ruiteri in having the dorsal setae on the preanal appendage much more slender than the denticles on X (these setae as robust as denticles on X in A. ruiteri ); in having the large, transverse denticle on the inferior appendage terminal and continuous with posterioventral margin of inferior appendage (at 2/3 length of appendage and on inner face not contacting ventral margin of appendage in A. ruiteri ), and in having the small, proximal denticle of the inferior appendage (ventral view) halfway between the ventral shoulder and the distal denticle (on the ventral shoulder in A. ruiteri ). Also differs from A. ruiteri in having the denticulate, vertical, posterior process of X non-flexible, extending only slightly above the dorsal margin of X, and with denticles forming 2 irregular rows (posterior process of X flexible, about 1/2 of denticulate portion extending past dorsum of X, and with denticles arranged mostly in a single row in A. ruiteri ). An additional character that may prove to consistently differ between A. minutus and A. ruiteri is the transverse band of ventral setae near distal margin of IX (triangular patch of setae, apex pointed forward, in A. ruiteri ).

Description. Male. Length 4.5-6.0 mm (n = 16). Male genitalia: Lateral view ( Fig. 20a ), anterior margin of IX sinuate, concave near dorsal margin, sloping down and forward at 45 o angle to below midline, then down and back at 10 o from vertical to convex ventral margin; dorsal margin appears to have a pointed posterior projection, but, at 200X, there is a vertical boundary extending from the tip of the point to what appears to be the sclerotized anteriodorsal portion of X; dorsal margin length = 3/4 length of preanal appendage, 1/2 length of ventral margin; posterior margin slightly concave, nearly vertical. Preanal appendage 1/2 length of inferior appendage, slightly expanded at tip, ventral margin convex, dorsal margin concave near base, length 3 times maximum depth, about eight long, erect setae on distal 3/4. Dorsal base of preanal appendage with dorsal projection that extends to level of dorsal margin of X, and appears as a triangular, sclerotized area at the dorsal base of X. Segment X sclerotized along ventral margin, sclerotized area gradually more transparent dorsad and not clearly differentiated from membranous dorsal portion of X. Ventral arm of X not clearly defined; ventral margin curves down and back from base, nearly straight and horizontal to upturned at 30 o for most of its length, then upturned at 90 o or recurved at posterior margin; pointed tip of posterior margin extends slightly above dorsal margin of X, with about 15 darkened, upturned denticles along posterior and lateral margins. Inferior appendage same length as X, length = 2.5 times depth; dorsal margin horizontal, slightly concave near middle, a horizontal lateral carina extends from base nearly to tip along dorsal 1/4. Ventral margin of inferior appendage slightly concave on basal third, forming a rounded 140 o angle with distal 2/3 which is also slightly concave. Tip of inferior appendage rounded, about 1/2 its maximum depth; tip of terminal denticle visible as a dark spot on inner surface of appendage at posterioventral margin; smaller denticle often visible on ventral margin halfway between terminal denticle and obtuse angle at 1/3 length.

Dorsal view ( Fig. 20b ). Anterior margin of IX deeply concave, U-shaped; mid-dorsal length 2/3 length of preanal appendage, posterior margin a faint, pale line just posterior to the tip of a triangular projection on midline. Preanal appendages with distal portion straight, divergent from body axis at 20 o angle. Ventral arms of X nearly parallel, slightly concave laterally; denticles on upturned distal arms conspicuous. A darkened triangular projection extends laterad at about 1/2 length of X, from mid-depth of X, this projection shielded by the preanal appendage in lateral view; dorsal portion of X membranous between sclerotized sides.

Ventral view ( Fig. 20c ). Anterior margin of IX concave; posterior margin concave on each side of pointed projection (100 o angle) between bases of inferior appendages; transverse linear array of setae present 1/3 distance from posterior margin, area posterior to this depigmented. Inferior appendages with outer margin nearly straight and slightly divergent from body axis to bluntly pointed tips; inner margins in contact at base, narrowly divergent from each other (30 o angle) to shoulder at basal 1/4, then more divergent and concave to and continuous with base of large, transverse, subterminal denticle (posterior base of denticle is nearly terminal). A second smaller denticle on inner, ventral margin midway between subterminal denticle and shoulder of inferior appendage, this denticle occasionally vestigial. Inner margins of sclerotized arms of X (not shown) converge from base of preanal appendages, in contact at 1/3 length, and divergent to tips; outer margins parallel to inner margins; lateral denticle at mid-length on mid-sides of X not conspicuous.

Larva. Head, notal sclerites, and anal claws brown; other sclerotized areas paler except for usual dark sutures/margins typical for genus. Mesonotal sclerites with outer third darker than mesal 2/3. Frontoclypeus with a tight cluster of four pale muscle scars in middle of posterior 1/2 of sclerite, two small ones anterior and more noticeable than the larger, less conspicuous posterior pair, these visible on shed sclerites of MMTs, but not on larvae. Genae with about 10 pale muscle scars in posteriolateral corner, these more conspicuous than the about 30 pale muscle scars posterior to the pale eyespot. Pronotum with about 15 pale muscle scars on posteriolateral 1/2 of each sclerite. At least some of the muscle scars on genae and pronotum visible on larvae.

Emergence dates. 22 May-5 July, 13-23 September.

Distribution. DE Newcastle. KY Bell, Breathitt (2), Edmonson (3), Lewis, Whitley. MA Worcester. NC Haywood (2). NY Colden, Tompkins. PA Chester (2), Crawford, Pike, Warren, Westmoreland. TN Blount (17), Campbell (2), Cocke (3), Fentress, Grainger, Knox, Sevier (13), Sullivan, Unicoi, Union. VA Giles, Tazewell. WV Preston.

Discussion. So similar to the allopatric and more southerly A. ruiteri that we felt compelled to compare the type of A. minutus with males of A. ruiteri to determine whether they represent one, two, or perhaps even three species (upstate New York type locality for A. minutus is far north of any other A. minutus material we were aware of at the time). In east Tennessee, A. minutus is widespread as far southwest as the Abrams Creek system and northern tributaries to Chilhowee Reservoir (north side of the Little Tennessee River); on the south side of the Little Tennessee River (Citico Creek system), the very similar A. ruiteri occurs, and it extends to the southwest through the Hiwassee and Conasauga river systems. The widespread A. minutus has been found to differ consistently from the localized A. ruiteri in numerous characters associated with male genitalia (see Diagnosis). Taken with A. iridis and A. kirchneri .

Etymology. Presumably in reference to the small size of this and all species of Agapetus .

Figures

Figure 19-21. Agapetus spp. male genitalia. 19) Agapetus meridionalis Etnier, Parker, and Baxter. 19a, lateral view; 19b, dorsal view, inferior appendages not shown; 19c, ventral view of IX and inferior appendages. 20) Agapetus minutus Sibley. 20a, lateral view; 20b, dorsal view; 20c, ventral view of IX and inferior appendages. 21) Agapetus pegram Etnier, Baxter and Parker. 21a, lateral view; 21b, dorsal view; inferior appendages not shown; 21c, ventral view of IX and inferior appendages.