The Yuma Skipper is a member of the family Hesperiidae, the large worldwide family of butterflies known as skippers. In Washington State most of our skippers fit into two subfamilies, the Pyrgine or “spreadwing” skippers, and the Hesperine or “grass” skippers. In Washington there are 29 species of skippers, 17 of which are grass (monocot) skippers. The grass skippers include the genus Ochlodes, which is represented by two species in Washington.

Like all grass skippers those in the genus Ochlodes often hold their wings in two planes, the hind wings horizontal and the forewings elevated at an angle. A common alternate position is with both wings held together over the back, with only the ventral sides visible. Skippers in the genus Ochlodes are typified by orange wings with poorly contrasting yellow spots on the ventral hindwing (vhw). While Ochlodes sylvanoides, the Woodland Skipper, is enormously abundant in late summer, the considerably larger 0. yuma  is rare in Washington, occurring only in marshy areas with Common Reed (Phragmites communis), its larval foodplant. The Yuma Skipper does not venture far from its aquatic host plant, and may be found flying among dense vegetation at the base of these tall grasses, or nectaring on nearby flowers. Ochlodes yuma has a late summer flight period and has been reported on the wing from late June to early September.

Within Washington State the Yuma Skipper is known only from an established population discovered by Jon Pelham at Dry Falls in Grant County, and from one or two tiny colonies along the Columbia River in Klickitat County discovered by Bob & Thea Pyle. The species occurs in small patchy colonies in several western states including Oregon, the Great Basin of California, western Colorado and points further south. While O. yuma apparently utilizes only the native variety of Common Reed, the very similar introduced European variety of the same plant is considered a noxious invasive weed by agricultural interests. As a result detailed mapping is now available showing stands of both varieties in Washington, which may make it easier for lepidopterists to locate new colonies of this rare butterfly.

0. yuma is single-brooded in Washington, reportedly double-brooded further south. The life cycle is poorly documented, but 0. yuma apparently overwinters in the egg or first instar larva (a second instar larva was recovered in Washington in the spring). Even the earliest instars create shelters by rolling the middle part of a Phragmites leaf into a circular tube ‘ and stitching it together with silk strands. The larva lives m the tube, venturing out, apparently at night, to feed on the tip of the shelter leaf.  When the leaf end has been consumed the larva moves to another leaf and creates a new shelter. Old abandoned shelters with their eaten leaf ends are easily spotted in proper habitat. The larva grows very slowly but reaches a surprisingly large size. In captivity pupation occurred within the leaf nest, but in the field many empty nests were examined without finding any pupae, suggesting that the mature larvae may wander to another location before pupating. On eclosing, 0. yuma adults stay close to their host plants, flying out only to nectar on adjacent flowers. Adult males can often be seen searching for females, flying slowly through dense vegetation at the base of the huge Phragmites plants, where poison oak is usually abundant.

The Yuma Skipper resembles the very common Woodland Skipper, but is much larger and usually less distinctly marked. The vhw yellow spot band may be virtually absent in 0. yuma, especially in males. While a small male 0. yuma might be confused with a large female 0. sylvanoides, there is a marked difference in size between comparable sexes. Males of 0. yuma can be distinguished from females by the presence of a black stigma on the dorsal forewing, by their smaller size and usually by less distinct yellow spots on the vhw.

All photos by Dave Nunnallee

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