The Western Tailed-Blue has been found only in the far northwestern counties. Here it can undoubtedly be easily confused with the more common Eastern Tailed-Blue. Nielsen says that this species is single-brooded in Michigan, but it is listed as double-brooded throughout southern Canada in Butterflies of Canada. Thus it seems likely that this species could be double-brooded in Wisconsin.
Weekly sightings for Western Tailed-Blue
Above, the male is blue with a black border, an obvious tail, and usually no orange spot near the tail. The female is essentially black, with some blue basally. Below, the Western Tailed-Blue is a light gray with a variety of small black marks, a small tail (often very hard to see on worn specimens), and a usually a small, single orange spot near the tail.
The Western Tailed-Blue should not be confused with any other Blue in the state except the Eastern Tailed-Blue. These two species are very easily confused in the field. In general, the Western Tailed-Blue has less orange below in the male (one spot versus 2-3 in the Eastern) and the female has some blue basally while the Eastern female is mainly dark above (although spring Eastern Tailed-Blue females may also show some blue in the spring).
Open, often disturbed areas.
The Eastern Tailed-Blue has 1-2 broods in Wisconsin. This species is considered to be double-brooded in southern Canada, but lack of data on this species makes it unclear if it is double-brooded in Wisconsin.
Uncommon in Wisconsin. It has been found only in the northwestern most counties. Since this species has been collected in northern Michigan, it seems likely that it might be present elsewhere in the northern counties of Wisconsin.