INVERTEBRATES FIRST CATERPILLAR OBSERVATIONS OF THE MORMON METALMARK BUTTERFLY IN NATIONAL PARK, SASKATCHEWAN

KATHERINE PETERSON, ESAYASAMOSA, 230A Earth Sciences Bldg, University of Alberta, Edmonton, AB, T6G 2E9; SHELLEY PRUSS, Parks Canada, #1550, 635 - 8 Ave, S.W. Calgary, AB, T2P 3M3; and NADIR ERBILGIN, 230A Earth Sciences Bldg, University of Alberta, Edmonton, AB, T6G 2E9

The Mormon Metalmark butterfly is on sparsely vegetated clay soil where the only species of the primarily tropical the primary host plant, the Branched lepidopteran family found Umbrella Plant ( pauciflorum) in Canada. The species is commonly grows. Mormon Metalmark caterpillars are found in arid regions of western North crepuscular and are typically active just America. Its range is relatively contiguous before sunrise and shortly after sunset. through , Nevada, , and Most of the morning observations were Colorado. Farther north, the populations conducted during twilight and thereafter become more disjunct.1 There are only for 3-4 hours, until the caterpillars sought two known Canadian populations, one in shelter out of view. A few observations the southern Similkameen River Valley of took place in the evenings, from sunset British Columbia, and one in the prairie until the caterpillars sought shelter for badlands of southern Saskatchewan, the night. We had relatively shorter primarily in Grasslands National Park.23 evening observations because the These populations are listed respectively caterpillars were active for a short period as Endangered and Threatened under of time (the longest evening observation the Federal Species At Risk Act.1 During was approximately 1 hour). Evening field work from May to August 2009, observations at all three butterfly sites we documented the first Canadian confirmed that the caterpillars actively observations of Mormon Metalmark forage briefly after sunset in addition caterpillars. to the longer morning feeding session observed in more southern populations During June and July, Mormon (J. Powell, pers. comm.). Temperature, Metalmark caterpillars were observed in rain, and wind seem to influence feeding Laouenan, Timmons, and 70 Mile Butte, behaviour: the caterpillars begin to feed in the West Block of Grasslands National earlier in the morning when temperatures Park, where metalmark butterflies had are between 8 and 20°C (caterpillars were been located in previous field seasons. observed feeding as early as 0405h on The first two sites are on gentle-sloping 17 June), and were not observed feeding coulee bottoms, and the third is on the when conditions were rainy, or coider than steep slope of a butte. All three are 8°C.

68 (1) March 2010 37 this will be confirmed in 2010 with a larger sample size.

We observed that Mormon Metalmark caterpillars feed on the leaves, flowers, and stems of the Branched Umbrella Plant (Fig. 2, see inside front cover, top). Young caterpillars (probably the first 3 instars) rarely seem to leave the host plant, as they are completely dependent on it for food and probably shelter. Older, larger caterpillars (4th and 5th instars) Figure 1. Mormon Metal mark caterpillar, were observed crawling away from their July 2009. J. Janelle host plants, into cracks in the soil and under rocks to seek shelter and possibly The caterpillars have a distinctive to avoid predators. Others crawled appearance, particularly the older into neighbouring Branched Umbrella caterpillars: the body is purple, with two Plants, perhaps expanding their foraging dorsal and two ventral rows of yellow opportunities. nodules from which protrude a clump of bristly black hairs and a single longer Mormon Metalmark caterpillars are white hair. The eyes and mouthparts are typically solitary foragers with one black and bulbous. The three pairs of legs individual on each plant; however, closest to the head are black, thin, and occasionally up to three individuals pointed, while the five pairs of prolegs were observed on a single plant. From (also called false legs) on the abdomen May to June, many umbrella plants are are pink, rounded, and fleshy. The first enshrouded with complex silk webbings four pairs are located on abdominal over all or part of the plant, but it is unclear segments 3-6, while the last pair of which species spins this webbing. The prolegs is located on the 10th abdominal metalmark caterpillars seemed only to segment (Fig. 1). The first caterpillar, shelter in very fine silk nests, as opposed observed on 4 June, was only 4 mm in to the thick, more visible silk coating many length and was confirmed to be host plants. Additional studies are needed mormo under a dissecting microscope. in order to determine the role of webbing in the life cycle of Mormon Metalmark The caterpillars had a staggered caterpillars. emergence, and individuals of different sizes and in varying instars at different Young caterpillars prefer to graze times were often observed in the same the upper surface of the umbrella plant umbrella plant colony on the same day leaves, whereas older caterpillars can (Fig. 2, see inside front cover, top). Table eat entire leaves, as well as flowerheads 1 summarizes the first wave of larval and leaf stems. Characteristic reddish- observations from June to July 2009. The brown damage on the plants is evidence largest caterpillars observed, throughout of feeding by young larvae (Fig. 3). After mid- to late July, were up to 25 mm foraging, the caterpillars typically descend long. Smaller larvae (15 mm) were also the main plant stems to seek shelter. The observed in late July. Caterpillar size and caterpillars used a variety of microhabitats appearance suggests that the Mormon such as areas under stems, in the soil or Metalmark has at least five instars, but leaf litter, cracks in the substrate, under

38 Blue Jay the same sheltering spots after feeding, suggesting that once an individual has found adequate shelter it tends to reuse the same area.

Caterpillars that were observed once per week from mid-June to mid-July for the duration of the morning feeding began to “fade away” when they reached 20 to 25 mm in length. We assume that many of these caterpillars had begun to pupate; however, our attempts to find some of these pupae on the plants and in the Figure 3. Branched Umbrella Plant with surrounding soil were unsuccessful. leaves eaten by Mormon Metalmark caterpillars, July 2009. S.D. Pruss Unlike the caterpillars, adult metalmark butterflies are active during the hottest hours of the day (mid-day to evening). We rocks, and under woody or dead plant observed our first mating pair mid-day on material on or at the base of the host 17 August (Fig. 4) in Timmons Coulee of plant. Occasionally, the shelter sites are Grasslands National Park. We suspect coated in a layer of silk so fine it is difficult that the individual with the larger body to notice until a caterpillar is observed size was the female, because butterfly crawling into a small silk tunnel. Many species with discreet generations in highly caterpillars were observed returning to seasonal climates often exhibit protandry,

Figure 4. Mating Mormon Metalmark butterflies, 17 August 2009 K. Peterson

68 (1) March 2010 39 Table 1. Mormon Metalmark caterpillar observations at Grasslands National Park, SK, 2009.

Site Number of Date range Number with Eriogonum caterpillars of host pauciflorum observed plants

Laouenan 8 4 June - 13 July 6 One plant on top of steep Coulee hillslope, five others on hummocky coulee bottom; on gentle west-facing slope

Timmons 9 22 June - 9 July 9 Hummocky coulee bottom; Coulee on gentle southwest-facing slope

70 Mile Butte 8 15 June - 14 July 4 Steep, sparsely vegetated south-facing slope

South 1 25 June 1 Top of a large, hummocky Gillespie hill, on northwest-facing side a form of sexual dimorphism wherein the and designate critical habitat, among males tend to emerge before the females other priorities outlined in the federal to establish territories and increase Recovery Strategy for this species,3 mating success.4 However, this early to ensure its protection and continued emergence suggests that males will often survival. be smaller, as they have not had as much time in their development to increase 1. COSEWIC. 2003. COSEWIC assessment and update status report on the Mormon metalmark energy reserves and body size.4 This first (Apodemia mormo) in Canada. Committee on the mating pair we observed remained joined Status of Endangered Wildlife in Canada. Ottawa, with no discernible movements for over an ON. Available at: http://www.sararegistry.gc.ca/ hour. We observed a second pair farther document/default_e.cfm?documentlD=261 east in Police Coulee on 24 August. This 2. HENDERSON, A., P. FARGEY, S. PRUSS and F. pair was constantly disrupted by the SPERLING. 2008. Early sighting of a rare butterfly, diving attacks of a small, persistent single Mormon metalmark, in Grasslands National Park, SK. Blue Jay 66:105-106. individual (likely a male), and the mating pair was forced several times to change 3. PRUSS, S.D., A. HENDERSON, P. FARGEYand J. its perch location on the umbrella plant. TUCKWELL. 2008. Recovery strategy for the Mormon Metalmark (Apodemia mormo) prairie population, in Canada. Species at Risk Act Recovery Strategy Our observations of Mormon Metalmark Series. Parks Canada Agency. Ottawa, ON. caterpillars are the first ever documented in Canada. Learning more about the 4. SINGER, M.C. 1982. Sexual selection for small size in male butterflies. The American Naturalist ecology of the caterpillar stage, estimating 119:440-443. population sizes, and understanding mating behaviour will help us to define

There is nothing pleasanter than spading when the ground is soft and damp. - John Steinbeck

40 Blue Jay