Butterflies: Tougher than You Think!

Most people would admit to having a minor interest or curiosity in butterflies… and why wouldn’t they? Butterflies are fascinating creatures that flit through the skies on colourful wings. As caterpillars, they eat an equivalent that would put any buffet-frequenting linebacker to shame. As pupae, they inhabit structurally beautiful chrysalises where they quickly change forms into the beautiful adults that float from flower to flower, sipping on nectar. The adult butterflies themselves are universal symbols of beauty, transformation, and grace. What you might not realise, however, is that although these beautiful creatures are fragile, they are far from weak. These fantastic insects wouldn’t be able to exist in forms as showy and large as they are without a couple of sneaky moves to deal with the harsh realities of life as an insect. The trick to surviving as a species is adaptation and in the case of butterflies – they’ve adapted to be tough!

Two-tailed Swallowtail – Papilio multicaudata by Bill Bouton (Wikimedia)

You are what you eat! Butterflies: flamboyant poison sacks and flamboyant poison sack mimics
The three-part life cycle of a butterfly can generally be described in six words. Larvae eat, pupae rest, adults mate. The caterpillar itself can be thought of as an growing, open tube. Food comes in, the tube grows, and waste comes out the other end. These caterpillars spend weeks eating as much as possible, becoming a butterfly is energetically exhaustive! To a predator like a bird or a ground beetle, these caterpillars might seem like a tasty snack.  Luckily, some caterpillars are able to fight back through specialising on toxic host plants. These toxins are then stored within the body through metamorphosis, and the emergent butterfly contains the same foul-tasting phytochemicals as the hungry caterpillar. To give the predators a warning of how horrible they will taste, these butterflies often have striking bright colours. This phenomenon is known as aposematism.

Some butterflies whose larvae specialise on non-toxic plants have evolved to look almost identical to a toxic butterfly. Perhaps the most famous example of this are the monarch butterfly (Danaus plexippus) and the viceroy (Limenitis archippus). Monarch caterpillars feed on milkweed plants (Asclepias spp.), which possesses latex sap riddled with foul-tasting and poisonous alkaloids. Viceroy caterpillars feed on willow and poplar trees. Despite not having the toxicity of the monarch, they possess the bright orange-and-black wings that scream ‘I will make you very, very sick!’.

Comparison between Monarch (L) and Viceroy (R) butterflies. Photo by PiccoloNamek; Wikimedia Commons

Need salt? No problem!
Though butterflies are normally pigeon-holed as nectar-feeders, lepidoptera cannot live on sugar-water alone. One element that has particular importance for butterflies is sodium. They receive sodium through ingestion of salty liquids; this behaviour is called puddling. The sources are varied, and interesting – ranging in nature from the edges of mud puddles to urine, carrion, faeces, sweat and tears! Some butterfly species have even been noted as opportunistic blood-feeders. Male butterflies tend to be more devoted puddlers than females, due to sodium being a crucial component of their ejaculate. Interestingly, one popular study demonstrated that virgin females had reduced longevity compared to their mated counterparts. In this species, female butterflies did not assume the role of puddling. This meant that females only gained sodium through receiving the males ejaculate.

Photo by Geoff Gallice; Wikimedia Commons

No time to look after the offspring? Why not trick another species into doing it for you?
The gossamer-winged butterflies (Lepidoptera: Lycaenidae) are the second most species rich group of butterflies on Earth. With an estimated 6,000 species fitting within its taxonomic definition – many species have developed close associations with ants. The nature of these relationships is rather complicated, some species have mutualistic interactions while in other species – the butterfly larvae parasitise ant colonies. In their safe subterranean haven these caterpillars gorge themselves silly on honeydew and ant larvae. The larvae and the pupae of Lycaenidae have even evolved to smell and look like ant larvae. With formidable protection, and ample resources – Lycaenids larvae can have a lush upbringing – on the condition of keeping their secret identity concealed.

Winter coming? Chill out, hide, and grind your metabolism to a halt.
You might have wondered, where butterflies go during the winter months. The general strategy for most insects, is overwinter as an egg.  Many butterflies in the United Kingdom, and around the world have taken a secondary approach by going into hiding. As we sit around merrily by the fire in our warm sweaters, and knitted socks – butterflies cram into caves, and hollow trees. Some butterflies find nice cosy places to hide within leaf litter. Some butterflies like the morning cloak (Nymphalis antiopa) are able to squeeze their way under the bark of trees. When the first warm days of spring come around,  these tough butterflies wiggle out of their hiding spots; rejoining the world – ready to disperse and mate ahead of the competition.

Morning Cloak (Nymphalis antiopa) – Finland. Photo by Petritap; Wikimedia Commons

Not into standing still? Move!
The butterflies that aren’t interested in spending the winter in the cold have adapted a different strategy to keep ahead of the game – migration. The most celebrated, and arguably most impressive migrations is the gruelling journey made by the monarch butterfly. This North American species is well known for its fascinating voyage that begins on milkweed patches distributed across the United States and Southern Canada, eventually leading the butterflies to coastal California, and Mexico.  Some butterflies have been logged to travel more than 5,000 kilometres to their Mexican overwintering site. Monarchs travel only during daylight, and despite being limited by photo-period are able to travel this distance in a mere 8-10 weeks. After hanging out in Mexico for a bit of sun and relaxation, the monarchs mate and their progeny slowly make their way Northward from Mexico in multiple overlapping generations.

Monarchs in Flight. Photo by BrockenInAGlory; Wikimedia Commons

Keep your eyes out for rough-and-tough butterfly behaviour happening around you! As the weather gets a bit warmer, you’ll have a chance to observe some of these fantastic creatures within the comforts of your own backyard! Tough as nails, colourful as jewels, and more resourceful than McGyver – these phenomenal creatures will never fail to impress! So spread the word, indeed our colourful little friends are not as delicate as they first appear.

References

Pivnick, K. A., & McNeil, J. N. 1987. Puddling in butterflies: sodium affects reproductive success in Thymelicus lineola. Physiological Entomology, 12(4), 461-472.

Pierce, N. E., Braby, M. F., Heath, A., Lohman, D. J., Mathew, J., Rand, D. B., & Travassos, M. A. 2002. The ecology and evolution of ant association in the Lycaenidae (Lepidoptera). Annual Review of Entomology, 47(1), 733-771.

van Zandt Brower, J. 1958). Experimental studies of mimicry in some North American butterflies: Part I. The monarch, Danaus plexippus, and viceroy, Limenitis archippus archippus. Evolution, 32-47.

Wassenaar, L. I., & Hobson, K. A. 1998. Natal origins of migratory monarch butterflies at wintering colonies in Mexico: new isotopic evidence. Proceedings of the National Academy of Sciences, 95(26), 15436-15439.