An online resource based on the award-winning nature guide

Molting

Green-winged Teals Molting & Migrating

11-2-16-male-green-winged-teal-by-jeannie-male-moltingIn much of New England Green-winged Teals, our smallest dabbling (feed mainly on the surface rather than diving) ducks, are present either during the breeding season, or over the winter, but most of Vermont and New Hampshire have to settle for glimpses during spring and fall migration. Often these ducks stop to rest and refuel on shallow ponds, marshes and flooded fields. While occasionally one or two are spotted amongst a group of mallards, typically they are found in small groups that often congregate in large flocks.

The pictured male is soon to complete its fall “prealternate molt,” in which all body feathers except the innermost feathers of wing are replaced. When finished, he will sport brilliant cinnamon and green head feathers as part of his alternate, or breeding, plumage. Next July he will molt these feathers and acquire a duller basic, or non-breeding, plumage.   (Photo by Jeannie Killam)

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Grasshopper Wings Growing

7-21-16  grasshopper wings 092Grasshoppers experience incomplete metamorphosis, with three life cycle stages – egg, nymph, and adult.  A grasshopper egg hatches into a nymph, which resembles an adult grasshopper, except that it is smaller and lacks wings and reproductive organs.  Because of its hard outer exoskeleton, a growing grasshopper has to shed its skin periodically to accommodate its increased size.  (A larger exoskeleton develops beneath the old, smaller one that is shed.) Grasshopper nymphs molt several times (each stage between molts is referred to as an instar) before they reach their adult size, and with each molt, their “wing buds” get larger.  After the final molt, the wings are inflated and become fully functional.  Wings play an important part in grasshopper courtship, as males “sing” to attract females by rapidly rasping their leg against their forewing, a process called stridulation.

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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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