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Abdomen

Spiders Molting Exoskeletons

shed spider skin 052Like other arthropods, spiders have a protective hard exoskeleton that is flexible enough for movement, but can’t expand like human skin. Thus, they have to shed, or molt, this exoskeleton periodically throughout their lives as they grow, and replace it with a new, larger exoskeleton. Molting occurs frequently when a spider is young, and some spiders may continue to molt throughout their life.

At the appropriate time, hormones tell the spider’s body to absorb some of the lower cuticle layer in the exoskeleton and begin secreting cuticle material to form the new exoskeleton. During the time that leads up to the molt (pre-molt period), a new, slightly larger, inner exoskeleton develops and is folded up under the existing exoskeleton. This new soft exoskeleton is separated from the existing one by a thin layer called the endocuticle. During the pre-molt period the spider secretes fluid that contains digestive enzymes between the new inner and old outer exoskeletons. This fluid digests the endocuticle that separates the two exoskeletons, making it easier for them to separate.

Once the endocuticle is completely digested the spider is ready to complete the molt. At this point a spider pumps hemolymph (spider blood) from its abdomen into its cephalothorax in order to split its carapace, or headpiece, open. The spider then slowly pulls itself out of the old exoskeleton through this opening.

Typically, the spider does most of its growing immediately after losing the old exoskeleton, while the new exoskeleton is highly flexible. The new exoskeleton is very soft, and until it hardens, the spider is particularly vulnerable to attack.

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Meadowhawks Mating & Laying Eggs

9-30-24 autumn meadowhawks laying egg  043There is a genus of dragonflies, Sympetrum, referred to as meadowhawks, which emerge and fly in late summer and autumn, breeding in ponds and foraging over meadows. Mature males and some females of certain species of meadowhawks become bright red on part or all of their bodies. When breeding, the male grasps his mate behind her head with the appendages at the end of his abdomen and often does not release the female until after she has laid her eggs, which she typically does by dipping the tip of her abdomen in the water (see photo). The reason for this continued connection is related to the fact that a male dragonfly may remove sperm present in the female from any previous mating and replace it with his own packet of sperm, or spermatophore. In order to prevent this from happening, and to assure his paternity, a male dragonfly sometimes flies close to his mate, guarding her while she lays her eggs, or, in the case of meadowhawks, may fly in tandem with the female throughout the egg-laying process.

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