Grotella dis Grote 1883

Grotella dis Grote, 1883, Ann. Mag. Nat. Hist., ser. 5, 11: 55.

Diagnosis: Grotella dis, blanca, and parvipuncta form a close group of three sister species. In addition to these three US species there is a fourth species in southern Mexico, Grotella pyronaea Druce (1895) (= Antaplaga melanocrypta Dyar, 1912, NEW SYNONYMY). The forewing of dis is pure white with a few small black dots to represent the antemedial and postmedial lines. The postmedial line consists of two to four black points (the number is variable) and the antemedial line of two black points. The hindwing is heavily and uniformly suffused with gray-brown. This species can almost always be distinguished from parvipuncta because the forewing is pure white without the cream-white tinge found in parvipuncta. In addition the lateral margins of the front between the rim of the frontal process and the eye has dark gray to black scaling in dis, but cream-white scales in parvipuncta. This species and blanca are very closely related. Superficially the two are best separated by the color of the hindwing and the strength of the postmedial line. In dis the hindwing is uniformly suffused with gray-brown. The postmedial line dorsally does not contrast with the rest of the wing. In blanca the hindwing is not as heavily suffused with dark gray-brown and the postmedial line does contrast with the rest of the hindwing. There are only slight differences in the male genitalia. The valve of blanca appears to be slightly narrower and more sinuate than in dis. However the shape of the valve is variable in both species, and this is not a particularly good character to use in separating the two species. The best distinguishing character between the two species is found in the female genitalia. The ovipositor neck in dis has a covering of strong spine-like setae. The ovipositor neck in blanca has at most a fine covering of hair. The ovipositor lobes in dis tend to be slightly longer and more sharply pointed than in blanca, but again this is variable between individuals in both species. The Mexican species pyronaea is superficially almost identical to dis, but is slightly larger. The female genitalia are different. The spiney ovipositor neck of dis is absent. Also the corpus bursae of pyronaea is larger and wider than in dis.

Grotella dis and blanca could be confused with septempunctata or sampita. Grotella sampita has a series of black dots along the outer margin of the forewing. These dots are absent in the other three species. The hindwings of both septempunctata and sampita are white and are not uniformly suffused with dark gray-brown as in dis. The dots representing the postmedial and antemedial lines of hte forewing are stronger in septempunctata and sampita than in dis. More importantly the postmedial dot on the median vein is in a straight or slightly curved line in septempunctata and sampita, but in dis and blanca this point is located more toward the apex of the wing. If the dots of the postmedial line were connected with lines, they would trace a straightly to curved line in septempunctata and sampita, but a outwardly pointed triangle in dis and blanca. Wing length: mean = 11.78 mm, standard deviation = 0.65 mm, n = 10.

Adults have been collected in August, September, and October.

Distribution: This species occurs throughout most of New Mexico, western Texas, and eastern Arizona. It occurs sympatrically with blanca in Cochise county in southeastern Arizona. There is little variation in this species except for the strength of the black spots on the forewing. These spots vary from absent to distinctly present.

Identification Quality: Excellent

Larva: Unknown

Foodplants: Unknown

Similar Species

Grotella blanca

Grotella parvipuncta

Grotella septempunctata

Grotella sampita