Acronicta fallax, Schmidt, B. Christian, Wagner, David L., Zacharczenko, Brigette V., Zahiri, Reza & Anweiler, Gary G., 2014

Schmidt, B. Christian, Wagner, David L., Zacharczenko, Brigette V., Zahiri, Reza & Anweiler, Gary G., 2014, Polyphyly of Lichen-cryptic Dagger Moths: synonymy of Agriopodes Hampson and description of a new basal acronictine genus, Chloronycta, gen. n. (Lepidoptera, Noctuidae), ZooKeys 421, pp. 115-137: 118-120

publication ID

publication LSID

persistent identifier

treatment provided by

ZooKeys by Pensoft

scientific name

Acronicta fallax

comb. n.

Taxon classification Animalia Lepidoptera Noctuidae

Acronicta fallax   comb. n. Figs 2, 5, 9, 13

Adult morphology.

The fate of the genus Agriopodes   is anchored to the phylogenetic position of Acronicta fallax   , its type-species. Comparison of genitalic structure of Acronicta fallax   to all North American and most Eurasian Acronictinae   species reveals that genitalic features are most consistent with those found across an endemic North American group of Acronicta   species, consisting of Acronicta tritona   , Acronicta grisea   , Acronicta falcula   (Grote), Acronicta lithospila   Grote, Acronicta hamamelis   Guenée, Acronicta mansueta   Smith, Acronicta paralella   (Grote) and Acronicta vinnula   , here termed the tritona-group. Structural synapomorphies for these species are primarily those of the male genitalia (Fig. 5), including a short, claw-like clasper and a broad shield-like juxta (wider than long), with strap-like dorso-lateral extensions. The male vesica structure is moderately complex and consists of a sausage-shaped main chamber that curves ventrally then right laterally, which is armed with short, spade- to thorn-like spines to longer attenuated spines. The size and position of the vesica diverticula are unique, with thumb-like diverticula consistently present in the basal and sub-basal positions, and smaller diverticula variably present in the medial and apical positions. In females, the corpus bursae is relatively broad and rounded, shaped like a heart or a boxing glove with the appendix bursae forming the ‘thumb’ (Fig. 9). Females of the tritona-group (Figs 10, 11) lack the dense, persistent patch of fine, felt-like hairs between the 8th tergite and sternite that is present in the Acronicta hasta   -group. The hasta-group contains at least 14 species, largely corresponding to "Group II" of Forbes (1954). As also suggested by the placement of Acronicta superans   in our tree (Fig. 1), the hasta-group is related to the tritona-group, but exhibits a number of distinctive autapomorphies not present in either the tritona-group or Acronicta fallax   , such as a unique hourglass-shaped juxta; modification of the quadrate ventral process of the clasper into a broad, scoop-like flange and a dorsally curved pollex; and as noted above, a patch of persistent felt-like setae on the female A8 pleuron.

Structurally, Acronicta fallax   shows clear affinities to Acronicta grisea   and Acronicta falcula   of the tritona-group; the valve, clasper and uncus are much like those of Acronicta grisea   , with the clasper apex slightly less curved. The dorsolateral straps of the juxta are spinulose, and the medioventral portion of the juxta is produced into a rounded knob that is unique to Acronicta fallax   , although Acronicta tritona   shows a rudimentary form of this. Aedeagus and vesica structure of Acronicta fallax   are also similar to those of Acronicta grisea   and Acronicta falcula   , with two basal, unarmed diverticuli, a spinose main chamber, and a finely spinulose distal portion of the main chamber. The large spine field is composed of short, broad-based spines basally, and rounded, spade-like spines distally, similar to those found in Acronicta tritona   . The female genitalic structure of Acronicta fallax   is most similar to Acronicta grisea   (Fig. 10). Larval morphology does not offer support for a special association among Acronicta fallax   and tritona / falcula / grisea, although there is greater similarity of fallax to the tritona group than to larvae of the hasta-group.

Many Acronicta   species bear a prominent black basal, anal and apical forewing dash; the basal and anal dashes are sometimes transected by a crescentic line resulting in a dagger-like mark (hence the common name dagger moths). These forewing dashes typical of Acronicta   are also present in modified form in Acronicta fallax   , with the apical and anal dash (dagger marks) broadly joined to the postmedial line to form two roughly triangular postmedial patches. The basal dash is short and thick; and there is a black rectangular bar connecting the orbicular and reniform spots; the orbicular and reniform spots are occasionally and then only incompletely outlined. Unlike the green psaphidines ( Amphipyrinae   , Psaphidini   : Feralia   Grote and Miracavira   Franclemont), the green pigment of Acronicta fallax   is not sensitive to moisture degradation, where green changes to yellow upon exposure to high humidity (dried specimens of Acronicta fallax   can usually be moisture-relaxed without loss of green colouration). This suggests a fundamental biochemical difference in the green pigment of Acronicta   (found in Acronicta fallax   and Acronicta vinnula   ) compared to that of psaphidines.

Larval morphology and biology.

The immature stages of Acronicta fallax   were described by Dyar (1899), and Crumb (1956) gives a brief description based on a preserved larva. Illustrations are in Wagner et al. (2011) and McCabe (1991; head capsule and mandible). Dyar described the waxy-white egg as a flattened dome with about 48 radial ridges lacking transverse striae, 2 mm across and 1 mm in height–characters consistent with those of Acronicta   . Agriopodes fallax   shares structural similarities with members of the Acronicta hasta   and Acronicta tritona   species groups; head often with 6-8 dark (snowflake-shaped) spots over each somewhat quadrangular lobe, D1 borne from small wart on T1, and the ground colour tends to be green and body height highest through the anterior abdominal segments in both clades. Superficially, Acronicta fallax   shares greatest similarity with larvae of Acronicta vinnula   and kin, a member of the tritona-group, although We cannot identify its sister taxon with certainty based on our knowledge of its morphology, behavior and natural history.

The mature larva is bright lime to yellowish green with a whitish middorsal and somewhat broader subdorsal stripe, with body tapering posteriorly. The integument is covered with abundant, minute secondary setae in the form of spinules that are slightly thickened basally, giving the integument a velvety texture. With the exception of the D1 pinaculum on T1, which is brownish to red and borne from a small wart, the pinacula are nearly obsolete in the last instar, i.e. flattened, faintly brown or concolourous, and with short setae (pinacula are more elevated and reddish brown with longer setae in middle instars). The greenish head sometimes has paired dark spots above the frons and a field of 6-8 darker spots over each lobe, laterad to apex of frons. The head, usually retracted into the thorax, has a rough, granular surface but lacks secondary setae, and is about 4 mm wide when mature. The thoracic shield is lightly sclerotized; prothorax with XD setae longest on body, extending well forward; XD1 and D1 solitary; D2 setal cluster shifted forward and grouping with XD2 seta; SD and L setae grouped, each comprised of 8-11 setae. Nearly all primary setae are replaced with open but defined clusters of 6-12 setae. Abdomen with D, SD, and L setal clusters more or less vertically aligned; D2 in typical position on A7-A10; solitary seta present below L2 group, well forward of spiracle; L3 group a diffuse set of 9-12 setae; numerous setae in each subventral cluster. A8 spiracle approximately 2 × diameter of those on preceding segments. The anal plate and pinacula are ill defined or undifferentiated, with limits defined by clusters of microspinules, which are largest (some tooth-like) over the anal plate. Prolegs with 23-28 crochets. Length of larva at maturity is 28-30 mm. The prepupal larva turns waxy red, and tunnels into soft wood or spins a flimsy cocoon in a crevice. The larva feeds from the leaf underside of Viburnum   species, including Viburnum dentatum   L. ( Dyar 1899) and Viburnum nudum cassinoides   (L.) Torr. & A. Gray ( Wagner et al. 2011). Undoubtedly, other Viburnum   species are used also, particularly by northern populations beyond the range of Viburnum dentatum   and Viburnum nudum   . A record for poplars ( Populus   sp.) as a host cited by Tietz (1972) is certainly erroneous.