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Archive for October 14, 2015

Common Milkweed Seeds Packed in a Pod!

10-14-15 large milkweed bugs 095Congratulations to those of you who guessed correctly, and thank you to everyone who participated in this week’s Mystery Photo. I find patterns in nature both intriguing and beautiful — they will be the subject of more Mystery Photos! When photographing these Common Milkweed (Asclepias syriaca) seeds, I discovered that there were other creatures attracted to them besides myself – hence, today’s blog post:

Only two to four percent of Common Milkweed flowers eventually produce mature pods. Each pod contains an average of 226 seeds (all from one flower). Resembling overlapping fish scales, the seeds are arranged in a way that allows the wind to successively, from the top to the bottom of the pod, catch their silk parachutes and disperse them.

Just as milkweed pods are opening and seeds are maturing, Large Milkweed Bugs (Oncopeltus fasciatus) in all stages of metamorphosis (there are five nymphal stages, or instars) congregate on milkweed pods to feed on the seeds. (Their eggs are laid on milkweed plants.) Like all true bugs, their mouthparts (rostrum) are not adapted for biting and chewing food, but are designed for piercing and sucking. The rostrum consists of two side-by-side tubes. The milkweed bugs use one tube to pump digestive enzymes into the tough milkweed seeds and the other to siphon up the softened plant material. Like other milkweed feeders, milkweed bugs obtain poisonous compounds from the milkweed plant that are used for defense, and their orange and black coloration warns predators of their toxicity.

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