Noctuidae - Stiriinae

 

 

 

Stiria rugifrons Grote

Stiria rugifrons Grote, 1874, Bull. Buffalo Soc. Nat. Sci., 2:73.

Diagnosis: Stiria rugifrons and intermixta are extremely close morphologically and superficially. Stiria intermixta may be just the southwestern US Mexican race of rugifrons. The ranges of variability in both the male and female genitalia overlap and cannot be used to separate the two species consistently. The outer margin of the male sacculus before the clasper is slightly knobby in both species with small setae on the knobs. These knobs are usually, but not consistently, larger in intermixta than in rugifrons. The forewing median area along the inner margin is usually wider and more rectangular in rugifrons than in intermixta. This median patch is usually distinctly suffused with light gray scales in rugifrons, although this suffusion is visible only in fresh specimens. The forewing median area of intermixta is more square shaped and its color is browner than that of rugifrons. These superficial differences, however, do not consistently hold. The best recognition character, is probably range. Stiria rugifrons occurs primarily in eastern and central North America and intermixta in the southwestern United States and Mexico. Both species occur in Texas and Colorado, but their ranges are not known to overlap. In Texas rugifrons occurs in the northern Plains region of the state and intermixta is apparently limited to western and south central part of Texas. There is a third, closely related, but undescribed species, in central Mexico. This undescribed species is distinctly larger than either rugifrons or intermixta. It is sympatric with intermixta in the Mexico City region. Wing length from base to apex: mean = 19.45 mm., standard deviation = 1.39 mm., n = 10.

Distribution: Stiria rugifrons is one of the few species of the Stiriinae occurring in the eastern United States. This species is apparently rare along the east coast. I have seen specimens from northern Florida in the south as far north as Virginia and westward into southern Ohio, Indiana, and Illinois. The species is more widespread and common in the Great Plains and southeast. It probably occurs throughout the southeastern states. In the Great Plains it ranges as far north as the northern border of North Dakota and as far south as northern Texas. Stiria rugifrons has been collected in Saskatchewan and Alberta as well. The westward boundary of its range reaches the foothills of the Rockies in Colorado and Wyoming. Although the hindwing is usually pure white, some specimens have a slight brown suffusion along the outer margin, particularly females.

Identification Quality: Excellent

Larva: The larva has been reared in southern Ohio by Eric Metzler from Helianthus microcephalis Torr. & Gray (Asteraceae) who has kindly supplied me with color slides and notes. The foodplant is mostly found in disturbed habitats. The larva is characterized by a series of fleshy tubercles on the dorsum of each abdominal segment, the mesothorax, and the metathorax. Each abdominal segment has six tubercles. The two largest are located along the caudal margin of the abdominal segment. The lower half of each of these two tubercles is red and the upper half is black. A second pair of tubercles located near the cephalad margin of the abdominal segment. These tubercles are yellow-orange or orange and smaller and closer together than the larger, caudal pair. Finally there is a third pair of tubercles each of which is located half way between the spiracle and one of the larger, caudal tubercles. The dorsal and subdorsal surfaces of the abdomen are yellow shading into green below the spiracles. There are black blotches in the membranes between the abdominal segments. The abdominal prolegs are yellow to yellow-green. The head is black with a yellow patch on either side dorsal to the ocelli. The pattern viewed from a dorsal position is very disruptive and the larva is very cryptically patterned if the larva is sitting on the flowers of its foodplant. The adults fly in late summer through middle autumn. Eric Metzler (pers. commun.) states that the larva is much commoner than the adult.

Foodplants: The larva has been reared in southern Ohio by Eric Metzler from Helianthus microcephalis Torr. & Gray (Asteraceae)

 

Stiria rugifrons

 

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