The Mormo Complex in Southern California

The taxonomy of the fascinating mormo complex of butterflies isn't yet settled (at least not to everyone's satisfaction). In southern California, there are many distinctive populations of this group adapted to various species of wild buckwheats (Eriogonum), from the beaches to the deserts and high into the mountains. Some of these fly only in the fall; others only in spring; and some in several broods per year. Some are nearly all black on the dorsal side with relatively bold white macules, while others are mostly golden yellow or somewhere in between. Despite the variety in appearance, host plants and life-cycle timing, these were all thought of as a single species not so long ago. But now there are reasons to believe that there are at least four species involved, with perhaps a dozen subspecies in southern California alone. This may be an instance of butterfly populations in an early stage of speciation; things just aren't yet well-defined, complicating our attempts to give them meaningful names.

Our knowledge of these butterflies has increased significantly thanks to rearing and genetic studies, as well as careful observation by devoted amateurs who have noted places where two or more members of the complex co-exist without apparent blending. This page is intended to give a general overview of this interesting complex. These perhaps superficially-similar butterflies reward close attention, as the differences between populations are real and they uncover a long evolutionary story that continues to unfold right here in our backyard.

Three pictures of Apodemia mormo butterflies showing distinguishing characteristics

From left: golden A. mormo cythera, which flies in the autumn at Big Rock Creek; spring-flying A. dialeuca pratti from the Holcomb Valley near Big Bear, where it uses E. kennedyi as host; and the dark, E. wrighti-feeding "near mormo" fall-flying entity from along Wildhorse Meadows Road below Onyx Peak south of Big Bear. As distinctive as some of these are, looks alone aren't enough to identify all the various members of this complex. Timing, location and plant associations are important.

The mormo-complex in and around the Mojave desert in southern California has been described in terms of three "biotypes". According to a landmark 1991 paper by Gordon Pratt and Greg Ballmer ("Three Biotypes of Apodemia Mormo (Riodinidae) in the Mojave Desert," Journal of the Lepidopterists' Society 45(1), 1991, 46-57), these three biotypes are multiple-brooded (type 1); single-brooded and flying in the spring (type 2); and single-brooded and flying in the late summer or fall (type 3). "To determine whether these different biotypes are due to seasonal or host-related factors or to genetic differences, we reared a number of populations under similar laboratory conditions" (p. 48). They found that the three types maintained different development times under identical conditions. For instance, type 2 spring-brooded butterflies are characterized by long larval development times, from 5 to 8 months of the year. These go through the egg and pupal stages relatively quickly. Type 3 fall-brooded mormo, in contrast, have a much shorter larval stage and pass much of the year as eggs, then develop as larvae through the summer, pupating and emerging as adults in late summer or early autumn when they mate and the females oviposit, completing the year-long cycle. The eggs of these butterflies are also larger than those of type 2. The timing of diapause and larval feeding is adapted to the patterns of dormancy and growth of the buckwheat host, which is in turn adapted to its particular habitat. For instance, the spring-flying desert subspecies mojavelimbus has a long larval development time, and the host, E. fasciculatum, usually goes dormant during the summer. When the plant resumes growing (after sufficient rainfall), the larvae can resume eating. In type 1 (multiple-brooded) populations, eggs hatched relatively quickly, and larvae developed and pupated without long periods of diapause. These butterflies could go through the life cycle two or three times per year, thanks to the availability of edible plant material for the larvae most of the year. Under identical laboratory conditions, a multiple-brooded deserti could complete the life cycle three times per year, but the type 2 and 3 butterflies, even with fresh plants available all year, persisted in completing the cycle once per year, just as in nature.

The biotype concept (esp. in terms of broods and their timing) is helpful for coming to grips with the variety we see in these butterflies (at a minimum, the arrangement is useful). The fall-flying populations can be placed under the species name mormo. As for the spring-flying members, James Scott (in Papilio NS 18) considered them to be the species dialeuca, but this name may not stick, as true dialeuca may not actually be single-brooded throughout its range; we will have to wait to see, but for now virgulti is often used, while dialeuca is beginning to appear in lists, including my own (consider it a placeholder name). The multiple-brooded members in southern California can be considered virgulti, except for the easily-distinguished deserti, which may be a subspecies of mejicanus or a full species itself. Perhaps there are more species we're lumping together here (e.g. arenaria may be genetically distant enough from other virgulti to merit full species status), or it may be that there are better ways to describe these populations. Arrangement primarily (but not only) by voltinism (broods) seems to me to be a good first step and can be extended beyond the Mojave desert populations. So, tentatively, the complex can be organized like this for southern California:

One spring brood

Butterfly Host buckwheat Comments
Apodemia dialeuca pratti
Pratt's Metalmark
Eriogonum kennedyi There is a colony in the Holcomb Valley, just north of Big Bear Lake. Flies early May to mid-June. Prominent white macules. Described in Systematics pp. 795-6. My photos are from May 29th, 2009.
Apodemia dialeuca peninsularis
Peninsular Metalmark
Eriogonum wrightii ssp membranaceum San Jacintos to Palomar Mountain and Laguna Meadows. Flies from mid-May to late June but emerges earlier some years. I found a couple of peninsularis freshly emerged in a large patch of wrightii in the Laguna Mountains near the TL on April 17, 2008, so they can emerge earlier than once thought. Described in Systematics, pp. 805-6.
Apodemia dialeuca davenporti
Davenport's Metalmark
Eriogonum fasciculatum Flies April - May. The Type Locality is Walker Pass at 5300'; it is also in the Tehachapis, the Piutes, and above Jawbone Canyon and is usually found between 4000 and 6000 feet elev. Named after the estimable lepidopterist Ken Davenport. Described in Systematics, pp. 801-2.
Apodemia dialeuca mojavelimbus
Ord Mountains Metalmark
Eriogonum fasciculatum Found early April to mid-May at the southwest edge of the Mojave desert, the TL being the Ord Mountains near Hesperia. I've seen them on the north slope of the San Bernardinos, and around Valyermo. Described in Systematics, pp. 803-4.
Apodemia dialeuca dialeucoides
Whitish Metalmark
Eriogomun wrightii ssp. subscaposum Late May to early July from Sugarloaf Mtn to Onyx Peak, south of Big Bear in the San Bernardinos. Described in Systematics, pp. 804-5. Many have searched for this metalmark in recent years without seeing it; may be extirpated.
 

One fall brood

Butterfly Host buckwheat Comments
Apodemia mormo nr mormo
Mormon Metalmark (S. Bern.)
Eriogomun wrightii ssp. subscaposum Wildhorse Canyon and up to Onyx Peak, using same host as dialeucoides above, in some of the same places, but later in the year. Very dark; some have no orange at all.
Apodemia mormo nr mormo
Mormon Metalmark (Temblors, such as Cottonwood Pass)
Eriogonum nudum var indictum July to early October; discussed in Ken Davenport's book on Kern and Tulare Counties and in his Emmel update. Somewhat variable but many look like langei.
Apodemia mormo autumnalis
Autumn Metalmark
Several late-flowering Eriogonum species Late August to early October. Range includes southeastern California, as well as parts of Arizona, Nevada, New Mexico, and Utah. Described by the late George Austin in Systematics, pp. 561-2.
Apodemia mormo cythera
Cythera Metalmark
Eriogonum fasciculatum Populations characterized by a striking overall light yellow-orange aspect extend from the northwestern San Gabriels into the desert at Mojave River Forks as far as I can tell.
Apodemia mormo tuolumnensis
Tuolumne Metalmark
Eriogonum fasciculatum, wrightii, microthecum and poss. kennedyi The Mt Piños/Frazier Park area colonies flying beginning in the late summer can be called (near) tuolumnensis, though perhaps only for lack of a better name. A single-brooded mormo that flies late August through late September where pratti flies in the Holcolm Valley - and to the west as far as Santa Barbara Co. - looks similar to tuolumnensis: see Systematics p. 796. John Emmel calls it "near tuolumnensis"; there is a blend zone with nr. mormo to the southeast. I remember seeing this among normal virgulti north of Big Bear and believing it was different. In 2019, I came upon a colony of metalmarks in a wrightii patch in Lake of the Woods that was exactly as I remember the Big Bear entity. Ken Davenport has these as tuolumnensis.
 

Multiple broods

Butterfly Host buckwheat Comments
Apodemia mejicanus deserti
Desert Metalmark
Usually Eriogonum inflatum Desert flyer with gray hindwind background and large white macules. Larvae burrow into stalks of host Desert Trumpet. Flies with other mormo without blending.
Apodemia virgulti virgulti
Behr's Metalmark
Usually Eriogonum fasciculatum Fairly widespread and common, from the coast into the foothills, as well as the deserts and the mountains where the host flourishes. This is what one will see on California Buckwheat in the Santa Monica Mountains, for example.
Apodemia virgulti arenaria
Sand Dunes Metalmark
Eriogonum cinereum Flies at Playa del Rey near LAX property with El Segundo Blues. Described in Systematics, pp. 806-7. DNA studies suggest that phylogenetically, this metalmark branched off surprisingly early and may deserve full species status.
Apodemia virgulti nigrescens
Dark Metalmark
Eriogonum fasciculatum Dense colony at Colton near railroad yard. Darker than nom. virgulti. It also differs in that G. Ballmer found 80 larvae on a single buckwheat plant, whereas one or two is considered normal for virgulti. Described in Systematics, pp. 796-8.
Apodemia virgulti
Kernville/Greenhorn Mtns. entity
E. fasciculatum, nudum, and/or wrightii Double-brooded. Most are black like mormo. See discussion in Ken Davenport's Kern/Tulare book.

©Dennis Walker