This week in the woods, a red eft ventured out of the leaf litter in defiance of the dry conditions and flaunted its orange skin, more luminous even than the impending fall foliage. You might see this land-dwelling juvenile eastern newt more often than eastern newts in larval or adult life stages or other salamanders because of its diurnality, relative tolerance for dryness, and eye-catching brightness. It does love moisture, and its presence can indicate the forest health factors of clean water and intact canopy, but its rougher, thicker skin allows it to withstand brief appearances in the open, especially when seeking new water sources. The striking coloration may seem to leave these tender, awkwardly moving creatures vulnerable during such forays, but it serves as an indication of its toxicity to would-be predators, a strategy called aposematism: if a bird or snake becomes ill from eating a red eft once, it will avoid others in the future. (As Steve Faccio writes in this Outside Story article, the potent neurotoxin tetrodotoxin, found in eastern newts as well as pufferfish, is the most poisonous non-protein substance known to science.)
Three other aposematic species active now are the long-antennated red milkweed beetle, squat swamp milkweed leaf beetle (both photographed in a West Fairlee, Vermont, milkweed patch by Ann Little), and monarch (photographed in the same spot). These insects accumulate toxic cardenolides from milkweed consumption and signal their toxicity with conspicuous coloration. While resistant to the toxins, all three species risk gumming up their mouthparts with an excess of milkweed’s sticky latex and so manage the sap’s flow by strategically severing leaf veins and rubbing their faces clear against leaves. Monarchs will carry the unpalatable toxins consumed as a caterpillar through their lifetime, into the chrysalis and butterfly stages.
Yet another aposematic species in its adult stage, the viceroy is distinguishable from its flashy lookalike, the monarch, by the horizontal black lines across its hind wings and is just as unpalatable. As a caterpillar, it feeds on leaves of willows and aspens containing the compound salicin and sequesters salicylic acid in its tissue. As Loren Merrill writes in a recent Outside Story article, the monarch and viceroy are Müllerian mimics – species that have evolved to resemble each other and reinforce signals of unpalatability to predators. The adults pictured here with tears in their hindwings may have survived encounters with birds; both for their brightness and their false eyespots, the wings make for the most obvious place to strike, but they also contain the highest toxin concentrations, and one bitter nibble may be enough to deter a bird.
This white admiral also had a potential peck taken from a wing. A subspecies of the red-spotted admiral butterfly (Limenitis arthemis), the white admiral (Limenitis arthemis arthemis) also hybridizes south of here with another subspecies, the red-spotted purple admiral (Limenitis arthemis astyanax). While this individual appears nectaring, white admiral males often “puddle” together on scat, mud, rotten fruit, and animal carcasses in order to acquire sodium, amino acids, and water; Susan Shea describes the process and more about the white admiral in this Outside Story article.
Between now and October, these butterflies and others will confront the cooler months in different life stages. Shortened daylight hours around the beginning of September will trigger the year’s last generation of monarchs to begin migration to their Mexican wintering sites. Like the majority of our butterflies, the non-migratory viceroy will overwinter as a caterpillar, rolling itself up in a willow or poplar leaf, binding the leaf shut with a twig or silk strand, and entering a hibernatory state of diapause. The white admiral observed here, likely part of the year’s smaller second generation, has a window of one to three weeks to reproduce, and if it does so successfully, its offspring, the third instar caterpillar, will make a hard-shelled chrysalis in a host tree and wait out the cold. Species like coppers and blues that overwinter as eggs either deposit them on the twigs of hosts or in the leaf litter around their base so that they will have food when the plants sprout and leaf out in the spring. Species like the eastern comma (written about in April) use the most unusual strategy of overwintering as adults, and we can look forward to seeing them earliest of all in the spring.
What have you noticed in the woods this week? Submit a recent photo for possible inclusion in our monthly online Reader Photo Gallery.