An online resource based on the award-winning nature guide

Molts

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.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Canada Goose Goslings: Contour Feathers Replacing Down

Canada goose gosling 207Within 24 hours of hatching, downy Canada Goose goslings leave their nest and are capable of walking, swimming, diving and feeding themselves. Like many species of waterfowl, their growth is rapid. Contour feathers on their wings and tail begin to emerge in about three weeks (note wing feathers of gosling in photo). Feathers on a gosling’s head, neck and back are the last to appear. Just before a gosling develops the ability to fly, the last fluff of down, which is on top of its head, disappears.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


European Starling

European starling IMG_8398There was no fooling the vast majority of Naturally Curious readers! As unpopular as the European Starling may be, its plumage is impressive, especially at this time of year. The starling’s summer, or breeding, plumage shows purple and greenish iridescence, especially on the head, back, and breast. Following the annual mid-summer/fall molt, most head and body feathers have whitish or buff terminal spots. Through the winter, most of these light spots gradually wear away to produce a glossy black appearance in the spring.

Most creative Mystery Photo response (from Steve Adams): “ This one’s easy. The bird is Hazel Hainsworth. She was sweet but insane. Hazel had a huge hat made of all different kinds of feathers, and because she liked her scotch, her navigation skills were somewhat dull, and she always made a point of telling people she’d been lost in every state in the nation, including Alaska.”

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Caterpillars Molting

6-25-14 caterpillar molting 044A caterpillar is the larval stage of a moth or butterfly. It is the only stage that has chewing mouthparts, and therefore a caterpillar spends most of its waking hours eating. This consumption of food results in massive growth, making its skin/exoskeleton very tight. When this happens, a hormone called ecdysone is produced, prompting the caterpillar to molt, losing its old exoskeleton (to left of caterpillar in photo) under which is a new and larger exoskeleton. After the molt, while the new exoskeleton is still soft, the caterpillar swallows a lot of air, which expands its body. Then, when the exoskeleton hardens, it lets the air out and has room for growth. Caterpillars molt four or five times as they grow. Each different caterpillar stage is called an instar. (Photo: Forest Tent Caterpillar)

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Red Squirrel’s Winter Coat

2-20-14 winter red squirrel IMG_0220There is a marked seasonal difference in the Red Squirrel’s appearance due to its two annual molts (spring and fall). In the winter, a broad rusty-red band extends along its back, from its ears to the tip of its tail. The Red Squirrel’s thicker winter coat also includes ear tufts, which no other species of squirrel in the Northeast possesses. Come spring, when the squirrel sheds again, it loses its ear tufts and its new coat is closer to an olive-green color than red.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Common Loons Molting

9-30-13 molting loon MH_20091004_214955_3Loons begin a full body molt (minus their wings) in the late summer and early fall, prior to migration. The black and white breeding plumage of adult loons in summer is replaced by the gray-brown of winter. This process typically begins at the base of the bill and spreads across the head and over the upper back. The process of molting can extend through migration on into December.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Waterfowl Vulnerable When Molting

8-23-13 canada goose remains 043All North American birds replace their old, worn plumage with new feathers at least once a year, a process known as molting. Most birds have what is called a “sequential molt,” in which their flight feathers are lost one at a time (from each wing). This allows many birds to continue flying while molting. However, during their annual molt, waterfowl undergo a “simultaneous wing molt,” losing all of their primary wing feathers at once, preventing them from being able to fly for a month or more while their new primaries are growing in. During this period, they are extremely vulnerable, as this photograph testifies to. If you look closely at the remains of the Canada Goose’s wing on the right in the photograph (dark feathers), you’ll see that the new primaries have almost, but not quite, grown out of their sheaths, making them not yet functional. It’s apparent that this bird was unable to take flight during its molt in order to escape its predator.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com and click on the yellow “donate” button.


Follow

Get every new post delivered to your Inbox.

Join 3,619 other followers