Sunday, February 8, 2015

Emergence and old skins

Shed snake skin
I was out looking for the first signs of spring at Fort Worth Nature Center yesterday. Trout lilies and other spring ephemerals emerge about this time of year in Texas, and spring itself will be truly upon us in another month. The birds were chattering and excited. I only realized I had missed them upon hearing them call again.

Question mark butterfly
I jumped the gun a little on wildflowers, however. It's still a bit early for them, despite the taste of perfect weather we've had this week. I did see other signs of the new season. A neatly coiled snakeskin sat on top of crispy brown leaves. Its perfect placement made me think it hadn't been there all winter. I don't know when snakes normally emerge from hibernation in Texas, but February seems premature.

Question mark butterflies were also awake and flying in the sun. These butterflies overwinter as adults. They roost in crevasses in tree bark, but they break dormancy on warm days. I didn't see much for them to feed on, but they seemed compelled to flit about. I don't imagine that butterflies 'play', that's what it looked like they were doing.

I also found an empty silk moth cocoon dangling from a small shrub. I'm on the fence as to whether the cocoon is from this year or last. It is remarkably well preserved, and it is certainly well attached to its little twiglet, but in our region silk moths don't normally begin to emerge until March.

Native silk moths are enormous, fuzzy, and brightly marked. The sea green luna moth is one of the more familiar representatives. Silk moths have an outer silk cocoon protecting their pupa. The silk moth used for commercial silk production is the only fully domesticated lepidopteran. They don't exist in the wild.

Adult silk moths do not have mouths. They do not feed as adults- they live for a week or two and are entirely consumed by the need to breed. In fact, some moth watchers rear female moths in order to use their pheromones as bait to lure in males of the species.

A luna moth- a type of silk moth
Until yesterday I'd never wondered how these mouthless moths fight their way out of their cocoons without mandibles. Apparently they either split their cocoons with a built-in escape hatch that only works from the inside, or they exude silk dissolving chemicals ("cocoon-ase") to ease their emergence.

Snakes and silk moths are both taken as symbols of rebirth and renewal, so it is fitting that I found them while out looking for signs of the changing season. As for spring beauties and trout lilies, I'll just have to keep checking. I don't mind the task.

A closer view of the cocoon

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