Butterflies of New Mexico: The Skippers VI: Giant Skippers (Hesperiidae: Megathyminae)

by Steven J. Cary

Skippers (Hesperiidae). About a third of our butterfly fauna, ~110 species, belongs to this family, which is arranged into six subfamilies: Eudaminae, Pyrrhopyginae, Pyrginae, Heteropterinae, Hesperiinae and Megathyminae. Skippers earned their name because of their rapid, skipping flight, which is powered by a heavily-muscled thorax. All skippers have antennal clubs that are distinctively bent, curved or hooked. Larvae silk leaves together for nests and then hibernate there. Most subfamilies have distinct larval food preferences.

Giant Skippers (Hesperiidae: Megathyminae). Giant Skippers earn their name with large size and very stout bodies. This uniquely American group is especially diverse in the Southwest because their larvae depend on Agavaceae, a group of plants that thrives and diversifies in that region’s arid and semi-arid landscapes. New Mexico has seven different giant-skipper species. Yuccas host our three Megathymus species, while agaves, or century plants, host our four Agathymus species. In all cases, larvae bore into succulent leaves, roots or stems where they feed, make shelters, and pupate. Adults are larger than other skippers and, in the case of some species, are quite elusive. Much of what we know about giant skippers was learned by scientists who, thinking outside of the box, discovered how to find larval nests, drove around in search of ‘colonized’ stands of yucca or agave, harvested colonized plants, then reared larvae through to adulthood.


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Agathymus aryxna (Dyar)                Arizona Giant-Skipper (updated January 25, 2021)

Description. Arizona Giant-Skipper resembles Orange Giant-Skipper, but it is predominantly dark above, not so orange, with only a pale orange postmedian band. They are similar below, too, but Agathymus aryxna has more prominent white spots on the hindwing costa. Range and Habitat. Arizona Giant-Skippers have a limited range in southeast Arizona, northern Mexico and southwest New Mexico (counties: Gr,Hi,Lu). They inhabit Upper Sonoran Zone savannas, usually 4700 to 7000′ elevation. Their distribution approaches that of Agathymus neumoegeni and may yet be found to overlap it in Grant or Luna counties, where care is needed to ensure proper identification. Life History. Palmer’s Agave (Agave palmeri, Agavaceae) is the preferred larval host for Arizona Giant-Skippers. Mature larvae bore into undersides of the fleshy leaves. Flight. Arizona Giant-Skippers fly during the same season as Orange Giant-Skippers, but peaking and extending a little later. Our records span September 1 to October 24. Adults rarely seeks nectar, but instead prefer to buzz and whir around canyon mudholes and roadside puddles. In seeking electrolytes, they sometimes settle for the perspiration of butterflyers. Comments. This species is more easily photographed than most other ‘Megs.’

Arizona Giant-Skipper (Agathymus aryxna) Clanton Canyon Trail, Peloncillo Mountains, Hidalgo Co., NM; October 16, 2012 (photo by Elaine Halbedel).
Arizona Giant-Skipper (Agathymus aryxna) Skeleton Canyon, Peloncillo Mountains, Hidalgo Co., NM; September 23, 1989 (photo by Steve Cary).
Arizona Giant-Skipper (Agathymus aryxna) Cottonwood Canyon, Peloncillo Mountains, Hidalgo Co., NM; October 13, 1985 (photo by Steve Cary).

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Agathymus neumoegeni (W. H. Edwards)            Orange Giant-Skipper (updated January 25, 2021)

Description. Like most Megathymines, Agathymus neumoegeni is large and stout-bodied. Adults are bright orange above with a black wing margin and black patches. Undersides are grizzled gray with vague white bands. This species can be confused with Agathymus aryxna, which is darker and has different adult behaviors. Range and Habitat. Orange Giant-Skipper lives along the Mogollon Rim in central Arizona and southwest New Mexico (subspecies Agathymus neumoegeni neumoegeni), in the mountains of southeast New Mexico and west Texas (subspecies Agathymus neumoegeni carlsbadensis (D. Stallings & Turner), and in the Chisos Mountains of southwest Texas. Colonies occur within stands of the larval hosts in Upper Sonoran Zone canyons and middle elevation mountains, 4100 to 7000′ elevation. In New Mexico this beauty lives only in the south (counties: Ca,Ch,DA,Ed,Gr,Lu,Ot). Life History. Agave parryi is the preferred larval host throughout New Mexico, but Agave lechuguilla is sometimes used (both Agavaceae). Young larvae bore into leaf tips, feed for a few weeks, then hibernate over winter. Mature larvae bore into upper sides of leaf bases and feed on sap; fecal material accumulates outside the burrow. Pupation is within the burrow, protected by a silk cap over the hole. Flight. Orange Giant-Skippers are univoltine and fly late in the season. New Mexico records span August 29 to October 11, peaking in September. Unlike look-alike Arizona Giant-Skippers, male Orange Giant-Skippers patrol rocky hilltops and ridgetops, but adults also visit canyon mudholes. Comments. Agathymus neumoegeni carlsbadensis was described from specimens collected in Carlsbad Caverns National Park (Ed) in 1957.

Orange Giant-Skipper (Agathymus neumoegeni neumoegeni) Hadley Draw, Cooke’s Peak, Luna Co., NM; October 9, 1995 (photo by Steve Cary).
‘Carlsbad’ Orange Giant-Skipper (Agathymus neumoegeni carlsbadensis) Camp Wilderness Ridge, Guadalupe Mountains, Eddy Co., NM; October 11, 1998 (photo by Steve Cary).
‘Carlsbad’ Orange Giant-Skipper (Agathymus neumoegeni carlsbadensis) North McKittrick Canyon, Guadalupe Mountains, Eddy Co., NM; October 7, 1984 (photo by Steve Cary).

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Agathymus polingi (Skinner)            Poling’s Giant-Skipper (updated January 25, 2021)

Description. Poling’s Giant-Skipper is small, for a Megathymine. Dorsal patterns resemble those of Orange Giant-Skipper, being more yellow-orange than black. The hindwing underside may have prominent white bands. Range and Habitat. This butterfly’s distribution barely includes New Mexico, touching our extreme southwest corner in Guadalupe Canyon (county: Hi), 4600 to 5000’ elevation. It is more common to the south and west into Arizona and northwest Mexico. Life History. Larvae eat Agave schotti, a tiny species that grows on canyon walls. Larvae burrow into undersides of leaf bases. Flight. Adults perch on canyon walls near the host plant, often head-down. The one annual generation is on the wing in autumn; our few records span October 9 to November 20. Comments. Agathymus polingi may fly concurrently with Agathymus aryxna, but its small size makes it easy to distinguish. Its name honors O. C. Poling, a prolific collector in the Southwest in the late 19th century.

Poling’s Giant-Skipper female (Agathymus polingi) Guadalupe Canyon, Hidalgo Co., NM; October 9, 1983 (photo by Steve Cary).

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Agathymus mariae (W. Barnes & Benjamin)      Mary’s Giant-Skipper (updated January 25, 2021)

Description. Mary’s Giant-Skipper resembles Orange Giant-Skipper, with which it may be locally sympatric. It differs by having a darker upper side with orange spots that are smaller and paler. Range and Habitat. Agathymus mariae is a denizen of southeast New Mexico (counties: Ch?,Da?,Ed,Ot), but it also occurs south well into the Chihuahuan Desert of west Texas and northeast Mexico. Look for it near the foodplant, which grows, sometimes in impenetrably dense stands, on desert flats and rocky canyon walls, usually between 4000 and 5000′ elevation. Life History. Larvae require Agave lechuguilla (aka: shindagger) (Agavaceae). Mature larvae can create tunnels linking several leaf bases. Flight. Our few confirmed New Mexico records for adults all indicate a flight period between September 12 and October 14. They are most often seen perching on the ground near the host. Comments. Some vague reports from Chaves and Dona Ana counties need confirmation. Outings in search of Mary’s Giant-Skipper require care. The author still carries a lechuguilla leaf tip irretrievably embedded next to his right tibia.

Mary’s Giant-Skipper (Agathymus mariae) Rattlesnake Canyon, Carlsbad Caverns National Park, Eddy Co., NM; September 26, 2005 (photo by Steve Cary).

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Megathymus yuccae (Boisduval & Le Conte)      Yucca Giant-Skipper (updated March 15, 2021)

Description. Yucca Giant-Skipper is gray-black with a yellow-white dorsal forewing submarginal band and pale spots at the forewing costa. A frosted gray underside has a white spot at the hindwing costa. Females have a yellow band on the upperside of the hindwing. Range and Habitat. Megathymus yuccae occurs nearly coast to coast in the southern US. It occupies Upper Sonoran Zone savannas in much of New Mexico (all counties but DB,Gu,Ha,Le,MK,SJ,SM), 4500 to 8000′ elevation. It is New Mexico’s most widespread giant-skipper. Life History. Larvae bore into stems or roots of several Yucca species (Agavaceae). Larval hosts for Megathymus yuccae include Yucca glauca in eastern New Mexico and Yucca baccata in western New Mexico. Mature larvae enter winter and pupate in late winter. Flight. Adults fly in spring; New Mexico records span March 16 to June 21. Peak flight numbers are in March or April in southern New Mexico, shifting to May in northern New Mexico. Males establish territories in flattish, valley-bottom openings. From perches on prominent rocks or stumps, males patrol in broad, sweeping arcs, searching their domain for females. Comments. Most of our populations are Megathymus yuccae coloradensis (C. Riley). The host of other named local variants include: Megathymus yuccae navajo Skinner from Fort Wingate (MK); Megathymus yuccae elidaensis D. Stallings, Turner & V. Stallings from near Elida (Ro); and Megathymus yuccae arizonae (Tinkham) in the Bootheel (Hi). Megathymus yuccae reubeni D. Stallings, Turner & V. Stallings inhabits south-central New Mexico. Megathymus yuccae winkensis H. A. Freeman is found in Eddy Co. This diversity of forms may reflect a high degree of isolation between local colonies.

Yucca Giant-Skipper (Megathymus yuccae coloradensis) Guaje Canyon, Pajarito Plateau, Santa Fe Co., NM; , April 25, 1993 (photo by Steve Cary).
Yucca Giant-Skipper (Megathymus yuccae coloradensis) east slope Black Range, Sierra Co., NM; April 4, 2016 (photo by Steve Cary).
Yucca Giant-Skipper (Megathymus yuccae elidaensis) near Portales, Roosevelt Co., NM; April 4, 2011 (photo by James Lofton).
‘Reuben’s’ Yucca Giant-Skipper (Megathymus yuccae reubeni) San Andres Mountains, Dona Ana Co., NM; April 3, 2019 (photo by Rob Wu).

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Megathymus ursus Poling                   Ursine Giant-Skipper

Description. The wingspan of this, our largest skipper, may approach four inches. Ursine Giant-Skipper has blue-violet suffusion on the underside. The forewing upperside is dark brown with small subapical white spots and a submarginal band that varies from yellow to orange and from narrow to broad. Range and Habitat. Megathymus ursus has a limited distribution in Arizona and southwestern New Mexico (counties: Gr,Hi,Si). Much of what is known about its distribution was originally learned by finding immatures in the field, digging up host yuccas, and waiting for adults to emerge. Life History. Females place eggs on yucca leaf tips, primarily of Yucca schottii and Yucca torreyi in New Mexico. Larvae crawl down and bore into the root. Flight. Adults fly in mid-summer, generally June 20 to August 7, but are rarely seen. Most sightings of males have been on prominent hilltops. Ursine Giant-Skipper adults are not known to feed. Comments. Raymond VanBuskirk and Johdan Fine photographed a female as she went about the task of placing eggs (see below).

Ursine Giant-Skipper female (Megathymus ursus ursus) in flight near Clanton Canyon Tank, Peloncillo Mountains, Hidalgo Co., NM; August 7, 2020 (photo by Jodhan Fine)
Ursine Giant-Skipper female (Megathymus ursus ursus) Clanton Canyon Tank, Peloncillo Mountains, Hidalgo Co., NM; August 7, 2020 (photo by Raymond VanBuskirk).

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Megathymus violae D. Stallings and Turner Viola’s Giant-Skipper (updated March 15, 2021)

Description. As with Megathymus ursus, the wingspan of this, our largest skipper, may approach four inches. Viola’s Giant-Skipper looks very much like Ursine Giant-Skipper, from which it was only recently distinguished as a separate species. The forewing upperside is dark brown with small subapical white spots and a submarginal band that varies from yellow to orange and from narrow to broad. Range and Habitat. Megathymus violae has a limited distribution in central and southeast New Mexico (counties: DA,Ed,Ot,To,Va) plus west Texas, where it inhabits Transition and Upper Sonoran Zone areas with stands of the host. Life History. Females place eggs on yucca leaf tips, primarily of Yucca torreyi, but sometimes Yucca baccata. Larvae crawl down and bore into the root. Flight. In New Mexico, adults fly in early to middle summer, generally mid-June to mid-August 7, but are rarely seen. Most sightings of males have been on prominent hilltops. Viola’s Giant-Skipper adults are not known to feed, but they do go to wet soil. Comments. Megathymus violae D. Stallings and Turner, was described in 1956 from specimens collected at Carlsbad Caverns National Park (Ed).

Viola’s Giant-Skipper (Megathymus violae) Jeff Davis Co., TX; June 2, 2013 (photo by Cathryn Hoyt).
Viola’s Giant-Skipper (Megathymus violae) female, with egg on yucca leaf tip at right; Cattail Falls, Big Bend National Park, Brewster Co., TX; April 10, 2020 (photo by Cathryn Hoyt).
Viola’s Giant-Skipper (Megathymus violae) Christmas Mountains Oasis, Brewster Co., TX; May 5, 2019 (photo by Bill Dempwolf).

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Megathymus streckeri (Skinner)  Strecker’s Giant-Skipper (updated January 25, 2021)

Description. Strecker’s Giant-Skipper is black above with white spots or brown with large yellow submarginal spots. The hindwing beneath is gray-brown with a whitish postmedian band. Range and Habitat. Megathymus streckeri inhabits the High Plains from Montana south to Texas and west across the southern Rockies to Utah and northern Arizona. In sub-montane New Mexico, generally 6000 to 7500′ elevation, it inhabits shrubby foothill canyons. Farther downslope on the plains, generally 3500 to 6500′ elevation, Strecker’s perches and patrols amid sprawling yucca flats. Life History. Yucca glauca and Yucca intermedia (Agavaceae) are known larval hosts. Scott (1992) noted oviposition on Yucca intermedia near Logan (Qu). Larvae create silk-and-debris tents or galleries at the plant base. Flight. Megathymus streckeri completes one generation per year. Adults fly from April 6 to July 7, peaking in May on the plains and in June in the mountains. Adults perch on the ground or on low shrubs. When disturbed, they fly in agitated circles, often returning to a nearby perch. Comments. We have subspecies Megathymus streckeri streckeri in our mountains (counties: Be,Ci?,Li,MK,Ot,RA,Sv,SJ,SF,Ta,To?) and subspecies Megathymus streckeri texana (W. Barnes & McDunnough) on our eastern plains (counties: Co,Cu,DB,Gu,Ha,Le,Qu,Ro,SM,Un).

Strecker’s Giant-Skipper (Megathymus streckeri streckeri) near Bloomfield, San Juan Co., NM: May 20, 2001 (photo by Steve Cary).
Strecker’s Giant-Skipper (Megathymus streckeri streckeri) Caja del Rio Plateau, Santa Fe National Forest, Santa Fe Co., NM; May 29, 2017 (photo by Bernie Foy).
‘Texas’ Strecker’s Giant-Skipper female (Megathymus streckeri texanus) Ute Lake State Park, Quay Co., NM; May 4, 1989 (photo by Steve Cary).
‘Texas’ Strecker’s Giant-Skipper male (Megathymus streckeri texanus) Ute Lake State Park, Quay Co., NM; May 4, 1989 (photo by Steve Cary).

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