Plagiomimicus pityochromus Grote

Plagiomimicus pityochromus Grote, 1873, Bull. Buffalo Soc. Nat. Sci., 1:182.

Schinia media Morrison, 1875, Proc. Boston Soc. Nat. Hist., 18:123.

Diagnosis: Plagiomimicus pityochromus is a dark brown species. The forewing orbicular mark is often filled or partially filled with jet black. The amount of black filling in the orbicular mark is variable ranging from a large bilobed blotch to a complete absence of black scales. The two sister species of pityochromus are triplagiatus and expallidus. The three are easily separable by superficial appearance. Plagiomimicus triplagiatus is characterized by its bright coloration, a contrasting dark brown lower half of the subterminal line, and well marked white antemedial and postmedial lines. In contrast pityochromus is a uniform dark brown. Plagiomimicus expallidus is dull yellow brown and all the maculation is washed out. The differences between the three species in the male and female genitalia are minute. The male clasper of expallidus is slightly thinner and the ductus bursae slightly shorter than in the other two species. The spines in the basal spine row of the vesica are 3 ? as long as wide in pityochromus and triplagiatus, but only twice as long as wide in expallidus. Wing length from base to apex: mean = 14.05 mm., standard deviation = 0.68 mm., n = 10.

Distribution: This species occurs widely in eastern North America. In the east it occurs as far north as the New York City and Long Island region of New York and reaches as far south as central Florida. Plagiomimicus pityochromus is commonest in the midwest ranging as far north as Wisconsin, southwestern Ontario and Iowa and as far south as south-central Texas. The species has a spotty distribution in the southeastern United States. The western limit of pityochromus is in eastern Colorado. There is no discernable geographical variation in the species. Within-population variation in size exists. The major within-population variation, as noted above, is the amount of black scaling in the orbicular mark. The degree of definition of the reniform mark also varies.

Adults have been collected from August to early October.

Identification Quality: Excellent

Larva: The larva has been described by Crumb (1956) who records Ambrosia trifida L. (giant ragweed)(Asteraceae) as the foodplant, the larva feeding on the seeds and seed capsules. The larva is indistinctive. I am unable to determine the larva's original color from the preserved material I have seen. All the spines are on well defined pinacula, but the pinacula do not differ in color from the rest of the body. There are large, triangular areas on the dorsum of each abdominal segment that are vaguely marked with brown. The head is slightly speckled with brown. The cervical shield of the prothorax has a vague, white, w-shaped pattern with brown located between the three points of the "w". The larva is almost identical to that of expallidus except the cervical shield is slightly darker brown.

Foodplants: Crumb (1956) records Ambrosia trifida L. (giant ragweed)(Asteraceae) as the foodplant, the larva feeding on the seeds and seed capsules.

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