Adults of most species of Parectopa are strikingly-colored gracillariids, the color pattern of the forewing often being rusty brown with angled white dashes on the anterior and posterior margins. Larvae feed in upperside blotch leaf mines on both forbs and woody plants. Several species are known to occur in Illinois.
Parectopa robiniella (Fig. 1) is a commonly-occurring leaf miner on black locust, Robinia pseudoacacia (Fabaceae); it also has been reared in central Illinois from a woodland species of Desmodium (Fabaceae). The leaf mine, which is a flat, yellowish upperside blotch, somewhat resembles that of Chrysaster ostensackenella (which also feeds on Robinia) but differs in being characteristically irregular in outline, such that it is often termed "digitate" (i.e., having "finger-like" excavations all around the margins of the central blotch).
Figure 1. Parectopa robiniella. Adult, and early and mature leaf mines on black locust, Robinia pseudoacacia (Fabaceae).
The larva of Parectopa plantaginisella (Fig. 2) lives in a yellowish blotch leaf mine, on plantain, Plantago sp. (Plantaginaceae) and on fleabane, Erigeron sp. (Asteraceae). In the mature leaf mine, the upper and lower layers of leaf epidermis become widely separated, giving the mine a noticeably puffy appearance.
Figure 2. Parectopa plantaginisella. Adult, and leaf mine on fleabane, Erigeron sp (Asteraceae).
Parectopa occulta (Fig. 3) is a leaf miner on clover, Melilotus sp. (Fabaceae). Adults occur from June through August in Illinois, with a possible second generation emerging in October. The adult is similar in appearance to Micrurapteryx salicifoliella.
Figure 3. Parectopa occulta. Adult, reared from leaf mine on clover, Melilotus sp. (Fabaceae).