Epimartyria auricrinella Walsingham

Davis, Donald R. & Landry, Jean-Francois, 2012, A review of the North American genus Epimartyria (Lepidoptera, Micropterigidae) with a discussion of the larval plastron, ZooKeys 183, pp. 37-83 : 42-54

Epimartyria auricrinella Walsingham Figs 14 –51018-3233-5974– 80

Epimartyria auricrinella Walsingham, 1898: 162.- Kearfott in Smith 1903: 125.- Dyar 1903: 581.- Meyrick 1912: 6.- McDunnough 1939: 110.- Davis 1983: 5; 1987: 341.- Poole 1996: 716.- Djernaes 2011: 3.- Hashimoto 2006: 43.

Micropteryx Epimartyria auricrinella Walsingham.- Forbes 1923: 64.

Diagnosis.

Adult Epimartyria auricrinella are easily distinguished from those of the other members of Epimartyria in possessing uniformly dark fuscous forewings without the yellowish spots present in those species.

Adult

(Figs 1, 4-5). Head: Vestiture light orange brown. Antenna with vestiture of scape and pedicel concolorous with head; scales of flagellum dark brown to fuscous. Labial palpus cream.

Thorax: Dark fuscous with coppery to purplish luster. Tegula concolorous with head. Forewing dark fuscous with coppery or golden to purplish luster dorsally, less iridescent ventrally; fringe paler, more gray. Forewing length: 4.2-5.6 mm. Hindwing with scales over distal third nearly as broad, dark fuscous and iridescent as in forewing; scales gradually becoming more slender, more gray, and less iridescent over basal 2/3; fringe gray. Legs medium to dark brown dorsally, light brown ventrally and at apices of tarsomeres; epiphysis absent.

Abdomen: Piliform scales uniformly brown dorsally and ventrally. Paired glands of sternum 5 with muscle for opening glands originating on anterior edge of sternum 6 and inserted into each gland duct just inside aperature; gland reservoir slightly larger and more ovoid in female, but surrounding layer of secretory cells better developed and 2 –3× thicker in female ( Djernaes 2011, Djernaes and Sperling 2011).

Male genitalia (Figs 74-78): Caudal lobes of tergum X broadly rounded. Caudal apex of sternum X deeply divided, with apex of lobes acute, recurved; a pair of short, lateral lobes present near base. Valvae moderately long, ventral length nearly half the maximum length of segment IX; apex subacute and bearing a short, slender, recurved spine; a short, triangular, rounded process arising midway from mesal surface; elongate basal process ~ 4/5 the length of valva; distal margin of valva variable within populations from slightly concave to convex (Figs 78a-d). Dorsal branch of phallus cylindrical and smooth.

Female genitalia (Figs 79-80): As described for genus. Caudal end of genital sclerite moderately furcate as in Epimartyria bimaculella ; length of furcations ~ 0.2 that of relatively shorter, undivided base.

Larva

(33-59). Mature larva up to 5 mm in length. Body approximately hexagonal in cross section; color generally brown, lighter brown ventrally. Integument over dorsal half of body with a honeycomb-like surface of raised ridges (Figs 52, 58); integument of ventral half densely covered with micropapillae (Fig. 56) with an ext ensive plastron surface laterally (Fig. 52). Primary setae longitudinally ribbed, moderately slender, long, clavate.

Head: Prognathous and capable of being retracted into prothorax. Antenna elongate, slender, 3- segmented, arising posterior of clypeal margin and dorsal to stemmata; second segment the longest, ~ 2 × the length of basal segment; all antennal segments without sensory setae except for elongate terminal spinose seta. Five stemmata present, arranged in a tight circle. Adfrontal sutures vestigial, not extending to vertex; adfrontal ridges similarly undeveloped. Ecdysial lines externally indistinct. Tubular spinneret absent; external opening of labial salivary gland circular, relatively large, diameter ~ equal to length of second segment of labial palpus. Cranial setae reduced in length and number and concentrated over anterior third of head; stemmatal setae absent; a single medial (M) seta arising midway between antennae, without homology in other Lepidoptera but possibly homologous to campaniform sensillum in Trichoptera larva ( Kristensen 1998). Labrum with 6 pairs of primary setae and numerous spines along anterior margin; seta La 1 arising distad of anterior margin of labrum (Fig. 38). Mandible generally triangular in form with 3 acute cusps, the basal-most cusp the most reduced. Maxillary palpi relatively well developed, 3-segmented, with apical sensillae as in Fig. 46. Labial palpi reduced, 3 - segmented with minute apical segment bearing a long sensillum (Fig. 47). Intersegmental membrane between head and thorax covered with flattened, multidentate, scutate outgrowths (Figs 41-42).

Thorax: Prothorax with 7 primary tactile setae and 4 peg-like microsetae, the latter located along anterior margin of prothorax near the head- prothoracic fold; XD1 and XD2 greatly reduced to peg-like microsetae along dorso-anterior margin of prothorax below D2; L1 posterior to XD1; L2 below L1 and anterior to spiracle. MV1 and MV2 short, peg-like, below SV2 and closer to anterior margin of prothorax; MV2 about 2 × length of MV1. Subdorsal setae absent on all body segments. Meso- and metathorax with 5 primary setae and one microseta (SV2); L1 and 2 well developed and equal in size. Legs with 3 well defined segments and large pretarsal segment; 4- segmented including reduced coxa; pretarsal claw curved, elongate, ~ 1/3 the length of remainder of leg; axial spine at base of claw well developed; femur and trochanter fused, as well as tibia and tarsus; coxa with a bilobed and possibly eversible tactile vesicle located posterior-mesally near base of femur (Figs 48-49);

Abdomen: Segments 1-8 with 4 primary setae and 2 peg-like (L2) to spherical microseta (SV2); segment 9 with only D1 and L1; segment 10 with 2 microsetae, possibly representing D1 and L1. Spiracles peripneustic, located anteriorly in intersegmental fold on segments 1-8; spiracle raised to form a small dome with walls subdivided into ~ 10-12 fimbriated bands. Abdominal segments 1- 8 with short, fleshy, nonmuscular prolegs with rounded apices (Fig. 50); crochets absent in all genera of Micropterigidae .

Larval hosts.

Hepaticophyta : Lepidoziaceae : Bazzania trilobata (L.) S. Gray.

Pupa.

Unknown.

Biology

(Figs 9-10). The species occurs in shaded locations, in wet swampy woods, boggy ditches, or creek sides where leafy (moss-like) liverworts, the probable larval host, grow. Such habitats can be periodically or seasonally flooded. Larvae possess a plastron which indicates the capacity to live for short periods in a subaquatic environment or, at least in a habitat that is water-saturated. Adults are diurnal and are best obtained by gently sweeping the understory or clumps of liverworts ( Landry and Landry 1992). They can be seen perched on low foliage during the day and can be active even in early morning after sunrise (Figs 1-2). Mating was observed in the afternoon between 1200-1700H (JFL pers. obs.). Larvae obtained (by JFL) by placing in a Berlese funnel clumps of the liverwort Bazzania trilobata collected on 3 September 2000 at Lac Brûlé (Quebec) yielded larvae of two different size classes (3.4 mm vs 1.8 mm overall body length). This supports the previous observations by Davis (1987) that larval development probably spans over two years, at least in the northern part of the range, although adults emerge every year. One larva was found on the tip of a liverwort leaflet at the same locality in early October when the air temperature was around 5°C. Adults generally begin to emerge in mid May in the southern part of their range (Georgia, North Carolina) with April 30 being the earliest date recorded (from southern Maryland near Washington, DC). Further north the flight period is gradually delayed, with adults in northern New York and all of Canada active during the summer between mid-June and mid-July.

Holotype.

♂, USA: North Carolina, 1884, H. K. Morrison, Type No. 35325, slide BM 8947 (BMNH).

Material examined.

CANADA: NOVA SCOTIA: Baddeck: 1 ♂, 23 Jun 1936; 1 ♂, 30 Jun 1936, T.N. Freeman, specimens # CNCLEP00077282-00077283, slide MIC 1825 (CNC); Parrsboro: 1 (abdomen missing), 12 Jul 1944, J. McDunnough, (CNC). ONTARIO: Ottawa: 4 ♂, 19 Jun 1906, C.H. Young, slide USNM 16615 (USNM, CNC); 5 ♂, 20 Jun 1906, C.H. Young, slide USNM 34372, specimens # CNCLEP00077266-00077268, CNC slide MIC1822 (CNC, USNM); 1 ♂, 27 Jun 1906, slide USNM 98008 (USNM); 1 ♂, 12 Jun 1946, G.S. Walley, specimen # CNCLEP00077269 (CNC). Black Lake, N of Burgess Township: 1 ♂, 22 Jun 1974; 2 ♂, 1 ♀, 14 Jun 1975, J.A. Downes, specimens # CNCLEP00077277-00077280 (CNC). Moosonee: 1 ♀, 18 Jul 1934, G.S. Walley, specimen # CNCLEP00077288 (CNC). Orillia: 3 ♂, 26 Jun 1926; 1 ♂, 3 ♀, 2 Jul 1926, C.H. Curran, specimens # CNCLEP00077276 –00077270– 00077276, CNC slide MIC1823 (CNC). Thunder Bay: 1 ♀, Jul 1945, H. S. Parish. QUEBEC: Havre-Saint-Pierre: 4 ex., 3-17 Jul 2010, malaise trap, C. Bélanger. Gaspé Peninsula: Mont Albert: 2 ♂, 1 ♀, 18 July 1940, A. E. Brower, slides USNM 16621, 17501, SEM slide 18394 (USNM); 11 ♂, 1 ♀, 19 Jul 1940, 2♂, 22 Jul 1940; side Mt. Albert: 2 ♂, 2 ♀, wing slide USNM 16157, slides USNM 18396, 18408, 98007, SEM slide 18430, (USNM, CNC). Mansonville: 1 ♂, 18 Jun 1928, W.J. Brown, specimen # CNCLEP00077286, CNC slide MIC1824 (CNC). Ste-Agathe-des-Monts, Lac Brûlé, 46.0903°N, 74.26°W, 370 m: 11 ♂, 6 ♀, 26 Jun 1991, afternoon sweeping in swampy ditch with liverworts and mosses at edge of spruce forest, J.-F. Landry, specimens # CNCLEP00076615-00076631 (CNC); Lac Brûlé, 46.0909°N, 74.2756°W, 370 m: 9 ♂, 3 ♀, 8 Jul 1992, 2 ♂, 16 Jul 1992, day sweeping on shaded liverworts near boggy marsh, J.-F. Landry; specimens # CNCLEP00068799-00068800 (CNC, USNM); Lac Brûlé, 46.0903°N, 74.26°W, 370 m: 3 ♂, 2 ♀, 1 Jul 1993, afternoon sweeping liverworts and mosses, J.-F. Landry, specimens # CNCLEP00067565-00067569 (CNC); Lac Brûlé, 46.0885°N, 74.2789°W, 370 m: 1 ♂, 4 Jul 1993, day sweep in mixed forest, J.-F. Landry, specimen # CNCLEP00076570 (CNC); Lac Brûlé, 46.0909°N, 74.2756°W, 370 m: 4 ♂, 2 ♀, 7 Jul 1993, day sweeping in shaded spruce-birch forest swamp, J.-F. Landry, specimens # CNCLEP00076571-00076576 (CNC); Lac Brûlé, 46.0885°N, 74.2789°W, 370 m: 1 ♂, 9 Jul 1993, at mercury light in mixed forest, J.-F. Landry, specimens # CNCLEP00076577 (CNC); Lac Brûlé, 46.0885°N, 74.2789°W, 370 m: 1 ♂, 1 Jul 1996, sweeping ferns at forest edge in afternoon, J.-F. Landry, specimens # CNCLEP00076577 (CNC); Lac Brûlé, 46.0885°N, 74.2789°W, 370 m: 1 ♂, 30 Jun 1997; 1 ♂, 1 Jul 1997, day sweep in mixed forest, J.-F. Landry, specimen # CNCLEP00076578 (CNC); Lac Brûlé, 46.0812°N, 74.2833°W, 370 m: 2 ♀, 1 Jul 1997, sweep in forest trail ca 18:00H, sunny, J.-F. Landry, specimens # CNCLEP00076580-00076581 (CNC); Lac Brûlé, 46.0919°N, 74.2756°W, 370 m: 13 ♂, 5 ♀, 2 Jul 1997, in swampy wood perched on vegetation 11:30 H– 12:30H overcast just before thunderstorm, J.-F. Landry, specimens # CNCLEP00076582-00076599 (CNC); Lac Brûlé, 46.0921°N, 74.2756°W, 370 m: 1 ♂, 1 ♀, 2 Jul 2000, afternoon sweeping liverworts and low vegetation in forest swamp, specimens # CNCLEP00067787-00067788, CNC slide MIC5756, DNA barcoded (CNC); 14 ♂, 5 ♀, 8 Jul 2002, day sweeping shaded liverworts near boggy marsh, specimens # CNCLEP00007712-00007720, 00068787-00068788, CNC slides MIC5753, MIC5755, MIC5757, MIC5758, MIC5760, MIC5762, MIC5763, 9 DNA barcoded (CNC); 6 ♂, 29 Jun 2003, in mixed forest swamp day-sweeping herbaceous and shrub vegetation, J.-F. Landry, specimens # CNCLEP00002816-00002821, CNC slide MIC5761, DNA barcoded (CNC); Lac Brûlé, 46.0881°N, 74.2788°W, 370 m: 1 ♂, 1 ♀, 4 Jul 2004, day sweep in forest swamp with liverwort, J.-F. Landry, specimens # CNCLEP00006682-00006683, CNC slide MIC5754, 1 DNA barcoded (CNC). Gatineau Park, Ramsey Lake, Hopkin’s Hole, 45.6025°N, 76.1079°W, 245 m: 12 ♂, 3 ♀, 11 Jun 1991, afternoon sweeping in forest swamp, J.-F. Landry, specimens # CNCLEP00076600-00076614 (CNC). Gatineau, Masham Township, 45.68°N, 76.05°W: 1 ♂, 26 Jun 1974; 1 ♀, 30 Jun 1974, D.M. Wood, specimens # CNCLEP00077284-00077285 (CNC). UNITED STATES: GEORGIA: Rabun Co: Chattahochee National Forest, Tate Br. Campground: 1 ♀, 16-17 May 1970, O. S. Flint, Jr. (USNM). KENTUCKY: Powell Co: 1 ♂, 23 Nov 1909, 1 ♂, 25 May 1924 (USNM). MAINE: Aroostook Co: Round Mountain: 1 ♂, 20 Jul 1956. Piscataquis Co: Greenville: 1 ♂, 9 Jul (USNM). Franklin Co: West Farmington: 1 ♂, 29 Jun 1966, A. E. Brower (USNM). Hancock Co: Acadia National Park, Mt. Desert Island: 1 ♂, 30 Jun 1933, (USNM). Penobscot Co: Passadumkeag: 1 ♀, 25 Jun 1938 (USNM). Piscataquis Co: Baxter State Park, Mt. Katahdin, Hunt Trail, 2400 feet: 1 ♂, 17 Jul 1948, bushes by brook, A. E. Brower, slides 16388, wing USNM 29861 (USNM). Sagadahoc Co: Woolwich: 1 ♀, 29 Jun 1965, A. E. Brower, slide USNM 33917 (USNM). MARYLAND: Montgomery Co: Cabin John: 1 ♂, 30 Apr 1921, A. Busck (USNM). MICHIGAN: Keweenaw Co: Isle Royale National Park: 2 ♂, 10 Jul 1957, R. W. Hodges (USNM). Emmet Co: Wilderness State Park, 45.7119°N, 84.9402°W, 180 m: 6 ♂, 30 Jun 1992, 17:00-18:00 hrs sweeping liverworts on banks of shaded stream in oak-pine forest with thuja, J.-F. and B. Landry, specimens # CNCLEP00068781-00068786, CNC slides MIC5752, MIC5764, DNA barcoded (CNC). NEW HAMPSHIRE: Rockingham Co: Hampton: 1 ♂, 6 –11– 1904, S.A. Shaw (USNM). NEW JERSEY: Essex Co: Essex Co. Park: 1 ♂, 3 Jun 1900, W. D. Kearfott (USNM). Essex Co: 1 ♂, 3 Jun; 7 ♂, 3 ♀, 8 Jun 1907, W. D. Kearfott, slides USNM 18409, 91794, 91795 (USNM). NEW YORK: Essex Co: [Keene]: Table Top Mountain, 3500 feet: 2 ♂, 1 ♀, 21 Jul 1940 (USNM). NORTH CAROLINA: Swain Co: Great Smoky Mountains National Park: Oconaluftee River at Towstring Road: 1 ♂, 11 May 1970, SEM slide USNM 17565 (USNM). Smokemont Campground and nearby: 2 ♀, 11-14 May 1970, slide USNM 33920, head slide 16614 (USNM). Whitewater River at rt. 171: 1 ♂, 18 May 1970, O. S. Flint, Jr. (USNM). PENNSYLVANIA: Dauphin Co: Inglenook: 1 ♀, 30 May 1911 (USNM). SOUTH CAROLINA: Pickens Co: Clemson, Wildcat Creek: 1 ♂, 25 Apr 1968, P. Carlson, J. Morse (USNM). TENNESSEE: Sevier Co: University of Tennessee Field Station, 35.739 °N, 83.4235°W, 503 m: 1 ♀, 22 May 2005, afternoon sweeping vegetation along forest creek, J.-F. Landry, specimen # CNCLEP00016403, CNC slide MIC5759, DNA barcoded (CNC). VIRGINIA: Falls Church: 1?, 1908, A. Busck, wing slide USNM 91787 (USNM). WEST VIRGINIA: Pendleton Co., Smoke Hole State Park, Briggs Run: 3 ♂, 2 ♀, 28 May 1977, [sweeping low vegetation 8-11 AM], D. & M. Davis, slide USNM 20690 (USNM).

Distribution

(Fig. 32). Epimartyria auricrinella occurs widely over eastern North America, in Canada from Nova Scotia to Ontario, and in the U.S. from Maine to Michigan and south to Tennessee and Georgia.

Remarks on larval morphology.

Chaetotaxy:Because the larvae of Micropterigidaelacksome thoracic and abdominal setae present in higher Lepidoptera , determining the homology of those setae present is subject to uncertainty. Various assumptions have been made as to which setae are present, based in part on their position to longitudinal muscle groups or to various body ridges ( Hashimoto 2001, 2006, Gibbs 2010), as well as to the generally accepted chaetotaxy of glossatan Lepidoptera ( Hinton 1946, Stehr 1987) which was followed by Davis (1987). Greatest uncertainty persists with the prothoracic chaetotaxy, where the number and relative development of setae can vary between different genera of Micropterigidae . Hashimoto (2001) concluded that the XD (of the prothorax) and the SD groups are absent in Micropterigidae , with the possibility that the two most dorsal of the four pairs of peg-like microsetae along the anterior margin of the prothorax in Epimartyria could be vestiges of one or more of these groups. The more ventral of the two microsetae along the anterior margin of the prothorax are believed to represent MV1 and MV2 present in most Lepidoptera , but homology of the dorsal pair is questionable. Because microsetae in this region are not known to occur on the prothorax of other Lepidoptera ( Hinton 1946), we have considered the dorsal pair to be homologous to XD1 and XD2 as suggested by Hashimoto (2001). Hinton (1946) briefly discussed the possibility that the XD group in higher Lepidoptera might be homologous to the microsetae of other body segments, but he argued that long tactile setae along the front margin of the prothorax represented instead a special setal group essential for protecting larvae, especially in those species with prognathous, retractable heads. In Micropterigidae it appears as if this protection has been compensated by several of the prothoracic tactile setae being directed strongly forward (Fig. 33). It may also be possible that several proprioreceptor (microscopic) setae homologous to those of higher Lepidoptera do not occur in Micropterigidae , and that all or most of the relatively stout microsetae present may represent greatly reduced tactile setae. Such reductions have occurred with the abdominal L2 and SV2 setae of Epimartyria (Fig. 33), D1 and D2 of Austromartyria ( Gibbs 2010), and D2 of Agrionympha ( Gibbs and Kristensen 2011). All microsetae of Epimartyria auricrinella are similar to the prothoracic microsetae in being relatively stout and greatly reduced it length (Fig. 33). Consequently, in this study we have largely followed the protothoracic chaetotaxy proposed by Hashimoto (2006) for the closely related genera Paramartyria and Neomicropteryx . The number and distribution of the prothoracic microsetae have not been well studied or illustrated in most genera of Micropterigidae . Better resolu tion of the prothoracic setal homology might become possible as larvae of more genera are discovered and studied.

Prolegs: The larval prolegs of Micropterigidae , which occur on abdominal segments 1-8 and 10, differ in their morphology from those of all other Lepidoptera where crochet- bearing prolegs are typically present only on segments 3-6 and 10. Hinton (1958) also reported muscles to be lacking in micropterigid prolegs, although this probably should be examined further in some genera such as Micropterix where the prolegs appear more developed and with more melanized, acute, clawlike apices (Figs 66-68). The anal prolegs of Micropterix are also distinct in forming a relatively broad, trilobed sucker (Fig. 66; Zeller-Lukashort et al. 2007).

Integumental specializations : Larvae of Micropterigidae often occur close to the ground in habitats more likely to be subjected to periodic flooding and drying. As an adaptation to such conditions, the larvae have developed an unusual cuticular morphology in the form of a physical gill, or plastron ( Thorpe 1950, Davis 1987), which provides extensive air–water interface for gaseous exchange. The aquatic larvae of several species of Crambidae have also developed special gills and plastron cuticles for breathing underwater ( Wichard et al. 2002).

An extensive plastron area has been observed in Epimartyria ( Davis 1987), and similar cuticular structures with various modifications appear in other genera of Micropterigidae examined. The plastron in Epimartyria auricrinella extends as a broad band laterally around the body between the level of the lateral (L1) and subventral (SV1) setae and then dorsally over the posterior margin of the prothorax (Fig. 33). The abdominal spiracles are located near the dorsal margin of the band at the extreme anterior edge of the segment (Fig. 52). The surface of the integument within this zone is densely covered with minute, irregularly shaped micropapillae (Figs 52, 55). Radiating out between adjacent micropapillae are dense series of even smaller ridges, aligned ~ 0.4-1.0 µm apart. Each ridge bears a single row of elongate, erect, knobby microtubercules ~ 0.2-0.4 µm in diameter and ~ 0.8-1.2 µm in length (Fig. 56). These minute structures are believed to help form an air film around that portion of the body (when submerged) that excludes water under normal hydrostatic pressure. Minute openings in the epicuticle are visible between the ridges (Fig. 57). These lead internally into an unusually complex, multichambered exocuticle reported by Kristensen (1990, 1998) in the larvae of Sabatinca and Micropterix . The basal layer of the exocuticle was found in these genera to possess small pores in each chamber which opened into a fluid- filled space between the exo- and endocuticle. Kristensen hypothesized the function of these unique cuticular specializations may be to assist in maintaining a water balance for larvae in a habitat subjected to periodic drying. An extremely thin, extracuticular pellicle covers much of the dorsal, lateral, and part of the ventral larval trunk to which small particles may adhere. The function and origin of the pellicle remain unknown. Immediately beneath the abdominal pellicle of Epimartyria auricrinella the exocuticle is divided into a series of honeycombed chambers (Fig. 58) resembling the condition Kristensen discovered in the larvae of Sabatinca and Micropterix .

The multidentate, scale-like cuticular outgrowths (Figs 41-42) covering the intersegmental membrane between the head and prothorax of Epimartyria auricrinella may further assist in a respiratory function. These structures superficially resemble the plastron scales present in certain Coleoptera ( Hinton 1969, 1976). The spiracles in Epimartyria (Figs 53-54) are also modified to prevent water entry. Each spiracle is raised into a small dome with finely divided, fimbriated walls. The spiracles in later instars of Neomicropteryx larvae are also conical with fimbriated walls, but the spiracular walls of the first instar are completely fused (i.e., solid) ( Hashimoto 2006) as they are in later instars of Sabatinca and Micropterix (early instars not examined). Spiracles of the first instar of Epimartyria have not been examined but may be similar to those of Neomicropteryx .

The larval plastron of Neomicropteryx nipponensis Issiki is similar to that of Epimartyria auricrinella in possessing a dense zone of minute, irregularly shaped micropapillae interconnected by dense radiations of smaller ridges bearing rows of knobby microtubercules (Figs 60-62). Scutate outgrowths also arise from the intersegmental head-prothoracic membrane (Fig. 63) as in Epimartyria . It is likely that larvae of all members of the northern hemisphere group of micropterigid genera proposed by Kobayashi et al. (2000) and Gibbs et al. (2010) have developed similar plastron specializations. In contrast, the external surface of the exocuticle of Micropterix (Figs 70-72) possesses a more extensive, regular arrangement of micropapillae, each ~ 10-20 µm in diameter, with ~ 6- 8 relatively stouter, often bifurcate, arm-like ridges radiating from a central disk. The ridges in Micropterix do not continue with those of adjacent ridges, but the extremities of each ridge are densely covered with microtubercules. Minute openings of variable size are present in the exocuticle of Micropterix (Figs 71-72),similar to those observed in Epimartyria and Neomicropteryx .