Part of being able to identify the moth at your sheet is knowing what’s flying in your area at that time of year. As the saying goes – timing is everything. There are certain groups that you can expect to see at certain times of year. For instance, the underwings are typically a summer to fall group, not encountered in the spring. Knowing what groups to expect at which time of year can help you to narrow down your possible options when trying to identify something, and also can help you to figure out what you should be looking for at your sheets.
In early spring some of the most common and conspicuous moths are in the genus Phigalia. These triangular, black-and-white moths are specific to the spring season. They emerge when the weather starts to grow mild and the sun warms the ground and trees, and can be seen even on cooler nights. There are four species in North America: The Half-wing (P. titia), Small Phigalia (P. strigataria), Toothed Phigalia (P. denticulata), and Walnut Spanworm (P. plumogeraria). There are also some species in Eurasia.
The females of all Phigalias are flightless, bearing just short nubs of wings. The individuals that show up at your sheet, therefore, are all males, and have the fluffy antennae the males use for detecting the pheromones of females. The different species can be difficult to separate from one another, as they share similar stripe patterns. The Small can be separated from the Half-wing by size, but the pattern and distinctness of the lines is the main key to ID. The Half-wing has a melanistic form that appears all black with subtle darker black markings.
Closely related to the Phigalias is the Spring Cankerworm, Paleacrita vernata. It shares similar life-history traits, such as the flightless females and early spring emergence. It is also mostly colourless, and similar in appearance to its sister species, White-spotted Cankerworm, P. merriccata, separable by the white dot on the forewing of the latter. It can sometimes be a very common species, an easy one to pick out and identify during the early spring period.