1959 Journal of the Lepidopterists' Society

COLLECTING INCISALIA MOSSI! (LYCA<:NIDA<:)

ON VANCOUVER ISLAND

by RICHARD Gu ppy

101

I ncimlia mossii H. Edwards is one of those butterflies whose local dis­tribution and restricted habitat produce an illusion of rarity. Possibly the above remarks apply to all scarce insects, though I suspect there are some species which do actually remain at a very low population density.

JONES (Annotated Check list of the Macrolepidoptera of British Co­lumbia) gives the distribution in B. C. as southern Vancouver Island, with a few scattered records for inland points near the southern boundary. In the Lepidopterists' News (vol.11: p. 58; 1957) there is a reference by H. K. CLENCH to I ncisalia mossii from Vancouver. I suspect that this should cor­rectly read "from Vancouver Island". The idea that Vancouver and Van­couver Island are the same thing is quite widespread, and will eventually cause some unfortunate mistakes. There is also a Vancouver in the State of Washington. The mixing up of the fauna of an island with that of the ad­jacent mainland is much more regrettable, from a scientific point of view, than would be the case if there were no water barrier.

On Vancouver Island I ncisalia mossii is confined to dry rocky areas where Sedum spathulifolium Hook. or S. oreganum Nutt. grows. In ten years of hunting the thing, I never thought to connect its presence with Sedum, until it was pointed out to me. Actually the butterflies seldom stray more than a few yards from their breeding sites, and as I eventually learned, you can live nearly on top of a colony and never see one at all. I must point out, in my own defense, that a good part of my trouble stemmed from the extremely early, and extremely brief, flight season of this butterfly. Actually I collected some speci­mens from IVIt. Benson, only 3300 ft., as late as June 10th. Ordinarily, the season at that elevation is no more than two weeks later than at sea level. The preceding winter had been one of unusually heavy snowfall, and it may be that this, always much deeper on the mountains, had by the slowness of its melt­ing, held things up that spring. But, nevertheless, the incident did nothing to increase my ambition to get after them early.

Before that time, I had seen a few specimens along the road a mile or so from my home, while engaged in business remote from butterfly collecting. I made some guesses as to where these had originated, guesses that were all wrong. I could have just about heaved a stone onto the point of origin of these butterflies, but I gave it little thought, becaw;e I had collected there several times and had seen no mossii. The main obj ect of my forays in this particular spot had always been the big skipper, Erynnis pro pert ius (Scudder & Burgess). This butterfly is just a bit later in first appearance than mossii, and it continues on the wing very much later. I supposed, however, that 1 was in time to get at least some stragglers of even the earliest species.

102 Guppy: lncisalia lIlossii Vol.l3: no.2

Most of the foregoing looks like a lot of lame excuses for having taken a long time to get on to a good thing. But at least it does emphasize the extraordinarily circumscribed flight activity of I ncisalia mossii. I have found in fact, that nearly all the Lyc<enid<e show in great measure this stay-at­home tendency. That the particular species under discussion seems more so than the others, may be due to the very short period when the adults are on the wing.

In 1957, while spending an afternoon with the Erynnis. as usual about the end of May, I netted a worn female I. mossii. I can say honestly that I decided right there on the plan of visiting the place earlier in the following year. But a few months later the Report of the Provincial Museum for 1956 came to hand. In this, among a number of host records for V. 1. Lepidoptera, G. HARDY briefly mentions Sedum spathulifolium as the food of I. mossii. I went back then for another look at my little patch, and noted that there was indeed a great deal of Sedum growing there. About that time I became fairly confident that 1 was not going very far for my I . mosszi specimens the fol­lowing spring.

This area presents a phenomenon fairly common on southeastern Van­couver Island, a patch of hillside on which the usual coniferous forest is n 'placed by scattered Garry Oaks and Arbutus. The soil in such places is either non-existent, or thin and sour, very wet in spring, and bone-dry later on. At the time of year when butterfly collecting commences, the aspect is far from barren. The greensward which stretches between the trees proves on close inspection to consist only in small part of grass, more of Camass, Buttercups and mosses. As many other wild flowers are present, the scene is one to delight the eye, and distract attention from the serious business of collecting.

T t may well be asked why, if this place is so attractive, I did not visit it more regularly. The reason is that another very similar area lies even closer to home, in fact one might almost say in my back yard. This is my home ground, the place for a quick look around whenever I have not the time for a trip further afield. It looks almost exactly like the other spot but no Sedum. therefore no I. rnossii. Why Sedu111 does not grow there I cannot say; it may be that it just never happened to get a foothold.

Tn 1958, of course, I was resolved really to watch the Sedum patch for mOH;i. The first butterflies were unusually early that year. I saw some In­cisalia iroides Bdv. and Blues around on April 10th, but then a spell of bad weather kept me waiting until the 20th before I could get out again. Most probably the mossii had been around as soon, or sooner, than the others. My best day was in fact the first day on the spot, when I got ten specimens. After that their numbers dwindled rapidly until May 10th, after which no more were to be found. 1 will compare this with the flight season of some other very early butterflies. Celastrina pseudargiolus Bdv. & Lee., Incisalia iroides, and Anthocaris sara Bdv. are usually around unt il the first of June. Erynnis propertius and Glaucopsyche lygdamus Dbldy. are perhaps a week

1959 Journal of the Lepidopterists' Society 103

later starting, but I have taken both species as late as mid-July, still in fairly good condition.

In addition to Mt. Henson summit, which I mentioned earlier, the only other locality for I. rnossii I have found is Thetis Lake Park near Victoria. In all three places I. mossii flies along with I. iroides, the proportion being about ten to one in favor of the latter species. These two are difficult to dis­tinguish at a little distance, but I learned to pass up the commoner species almost entirely, by only netting those insects which settled on low herbage. In all the collecting spots I have mentioned, Arctostaphylos uva-ursi Speng. grows in dense mats, and the theory I had formed, which died hard, was that I. mossii fed on this plant, while I. iroides preferred the taller growing Ericaceous plants, such as Arbutus or Gaultheria shailon Pursh. As far as iroides is concerned I was right, and as for mossii, I had just guessed the ",,-rang plant. This method of picking the species would be more nearly perfect if they were not both so fond of sipping from Arctostaphylos flowers.

I hate to remember now all the attempts I made to get I. mossii to ovi· posit. It is one of those insects which will just carry its eggs until it dies, rather than place them on the wrong plant. As soon as I tried Sedum, there was no trouble at all. As T am still too short of good specimens to waste any, I have not used many to obtain ova, but enough to provide a rough idea of the larva in its different stages. I was much interested to note that this cater­pillar has been a Sedum-eater long enough to have evolved a complicated sys­tem of protective colouration. The very young larVa! feed on the flowers of Sedum, and are yellow to match. When the flowers wither, the caterpillars transfer to the pink-tinged leaves, and later instars are pale pink in colour. I. iroides uses the same system adaJpted to its particular host plants. Feeding at first on white or pale >pink flowers , the larva is white. Becoming green later on, it then feeds on the unripe berries of Gaultheria or Arbutus.

Marine Drive, RR 1, Wellington, V. I., B. C., CANADA