Monday, June 1 Jen and I left Elm Creek for the Niobrara Valley Preserve located in Brown, Keya Paha and Cherry counties, arriving there about 10:00 am. As promised, the weather was warm, with temps already in the mid 80’s. Mainly we were looking for spring flying Duskywings (Erynnis sp.) whose larvae feed on oak and Northern Cloudywings. Chris Helzer had been to the Preserve the previous week and photographed some Dusted Skippers which the previous year had been found flying together with Northern Cloudywings. As it turned out we were way late for the Duskywings (spring is officially over) and were fortunate to find one Northern Cloudywing which were just emerging. For the day we sighted 15 species, four of which were new for the “Big Year”. They were Northern Cloudywings, Tawny-edged Skippers, Giant Swallowtails and Little Yellows.
We started out on a prairie hillside north of the river where we had found Dusted Skippers/Northern Cloudywings the previous year. The Dusted Skippers were there but no Northern Cloudywings. But there were Dusted and Tawny-edged Skippers and Melissa Blues. We checked a low muddy spot on the road and found Common Sootywings and Roadside Skippers there. After about an hour we moved on to Fairfield Road south of the river which proved to be the hotspot for the day. There we found a Giant Swallowtail, a Northern Cloudywing at a mud puddle and the Little Yellow. We followed the walking trail back east into the trees for a spell but finding little activity we tried a wet seep that we usually find productive. There we found Pearl Crescents and Eastern Tailed Blues. By this time it was 1:00 pm and the temperatures were in the mid 90’s. Not yet acclimated to the summer heat and feeling it we called it a day having found four new species for the year.
Northern Cloudywing – Thorybes pylades
Northern Cloudywing – photo from nature.mdc.mo.gov 
Range of Northern Cloudywing in Nebraska
While there has been one August record in Nebraska, Northern Cloudywings generally can be found flying in a single generation peaking in mid-June. Larvae feed on various legumes including Illinois Bundleflower and Round Headed Bush Clover. Adults frequent prairie hillsides and woodland margins.
Tawny-edged Skipper – Polites themistocles
Tawny-edged Skipper, male, female, side view
Tawny-edged Skippers are one of our most common skippers, being found statewide and flying in multiple broods from mid-May into late September. It’s larvae feed on various grasses. It can often be found in urban environments.
Giant Swallowtail – Papilio cresphontes
Giant Swallowtail 
Giant Swallowtail larvae on Gasplant
In Nebraska Giant Swallowtails can be found in colonies centered around naturally occurring Prickly Ash (Zanthoxylem americanum, a larval hostplant) or as wide ranging individuals. They can be attracted to your yard by planting rue (Ruta graveolens) or Gas Plant (Dictamnus species) upon which the larvae will also feed. Rarely a year goes by without a female dropping by the rue in my yard. Farther south the larvae can be a pest on citrus crops. Larger larvae resemble bird droppings. At the Niobrara Valley Preserve Prickly Ash is an abundant understory plant and Giant Swallowtails can be found there with some regularity.
Little Yellow – Pyrisitia lisa
Spring winds occasionally blow some southern species into the state and that appears to be the case with this butterfly. It cannot survive Nebraska winters so any Little Yellows found in the state are strays/vagrants. Larvae feed on a variety of legumes so seasonal breeding populations are possible. In Nebraska, most Little Yellow sightings are from the southeastern counties.
So with the addition of four species the “Big Year” list stands at 41.
One note on the Niobrara Valley Preserve – all buildings including the visitor center and restrooms are closed due to the Coronavirus so plan accordingly.