An online resource based on the award-winning nature guide

Metamorphosis

Spring Peepers Dispersing

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If you live near a pond where you heard loud “peeping” in late April or May, now is the time to keep your eyes peeled for young subadult Spring Peepers in the woodlands near the pond, for they are just completing metamorphosis and moving onto land. Thanks to their enlarged toe pads, peepers are good climbers but are usually found on the ground or low in shrubbery. The best time to look for young peepers is in the early morning hours and in the late afternoon, when they tend to feed.  Even if your timing is right, it can be challenging to find one — a full grown peeper is only ¾” to 1 ¼” long, and recently metamorphosed individuals are not much longer than ¼”, about the size of your baby fingernail. You’ll know it’s young because of its diminutive size and  its snub nose!

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Young Wood Frogs Getting Land Legs

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Thank you all for your good wishes regarding my next book!

With the dry weather we’ve been having, there is reason to be concerned about vernal pool residents, especially those that need to undergo metamorphosis before the pools dry up.  Granted, those amphibians such as Wood Frogs and Spotted Salamanders which transform into terrestrial creatures have evolved to have very quick life cycles, due to the temporary nature of their aquatic environment, but were they quick enough this year?

A very young Wood Frog crossed my path yesterday and answered that question for me.  No bigger than a raisin, it had to have emerged from its aquatic home in the very recent past.  When you think about the changes that have to occur between egg stage and adulthood (a total of two months, and it takes three of those eight weeks for Wood Frog eggs to hatch), it is mind-boggling.  Gills disappear and lungs develop, tail is absorbed, legs develop, mouth widens, intestines adapt to a herbivore-to-carnivore switch in diet – all inside of five weeks.

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Young Green Frogs Absorbing Tails

6-30-16  green frog metamorphosing 183Generally speaking, green frog tadpoles that hatch early in the season will transform into frogs by mid-to late summer.  Tadpoles that hatch late are likely to overwinter in their ponds and metamorphose late the following spring or early in the summer. Thus, the Green Frogs you see now with both legs and a tail spent the winter as tadpoles and are maturing now.

A specific process called “apoptosis” occurs as the tail is absorbed by the frog.  It involves programmed cell death, and occurs in various forms in multicellular organisms.   Humans experience apoptosis throughout their lives.  It is responsible for the separation of fingers and toes in a developing embryo, as the cells between the digits undergo apoptosis and it is responsible for the death of between 50 and billion cells each day in the average human adult.  Once it has begun, apoptosis cannot stop, and thus is a highly regulated process.

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Rosy Maple Moths Emerging, Mating & Laying Eggs

6-13-16  rosy maple moth 059Rosy Maple Moths (Dryocampa rubicunda) are easy to recognize, with their pink and yellow woolly bodies, pink legs and pink antennae.  Many adults are emerging from their pupal cases now, having spent the winter underground as pupae. Once metamorphosis is complete, the adult moths lose no time in finding mates and laying eggs, not stopping to even eat.  These members of the family Saturniidae are most active during the first third of the night, reducing their body temperature and activity in the morning and afternoon.

Mating takes place at night on the underside of a leaf, and 24 hours later the female lays clusters of 10-30 eggs (a total of 150 – 200 eggs) on the underside of the leaves of the larvae’s host plants, most often maples and oaks.  When the eggs hatch, the larvae usually remain on the same tree throughout their larval stage.

Known as Green-striped Mapleworms, the larvae initially feed together, but become independent feeders as they age.  Mapleworms change color as they develop.  When young, most have black heads and yellow bodies, but with age their heads turns reddish-brown and their bodies assume a shade of green.

In New England there is only one brood per summer; further south, there are multiple broods.

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Dragonflies Eclosing

5-26-16  dragonfly eclosing2  347 The sudden hot weather seems to have triggered a mass emergence of dragonflies and damselflies.  The emerging vegetation along the shores of ponds is covered with larval Odonates (members of the order of insects that includes dragonflies and damselflies) metamorphosing into adults.  The adults, still in the skin of their last larval stage, crawl out of the water, climb up vegetation, rocks, etc., and split the back of their larval skin.  The adult flips backwards out of this opening, hangs upside down and then grasps the vegetation and/or empty larval skin while as its abdomen is released.  The dragonfly hangs in the breeze while it pumps air into its body, sending liquid into its wings.

To appreciate this process called eclosion, compare the size of the wings in the photo insert (recently-emerged adult) with those in the larger photograph, which was taken twelve minutes after emergence.  Within a day or so the sheen on the newly-formed wings goes away, the dragonfly’s body hardens and colors start to appear.

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Spotted Salamander Larvae Soon To Emerge From Eggs

spotted salamander eggs2  040Roughly a month after spotted salamanders participate in frenzied courtship dances, deposit spermatophores (males) and take the spermatophores into their bodies (females), the resulting eggs have developed into larvae.  These juvenile, gilled salamanders are still contained inside the gelatinous eggs, but the eggs are dissolving fast, and the larvae will soon be swimming free within the vernal pools where the eggs were laid.

Many spotted salamander larvae do not survive this long.  Eastern newts, caddisfly larvae, leeches, fly larvae and even turtles feed on the nutritious eggs.  Meteorological conditions also contribute to the fate of spotted salamander eggs.  Their situation is especially precarious because they develop in vernal pools, which often dry up by summer’s end, thus forcing a rapid metamorphosis for amphibious inhabitants.  Hot temperatures can evaporate the water before metamorphosis is completed, and cool temperatures can slow down their development.  Inevitably some will survive to adulthood, and  the inch-and-a-half to two-inch salamanders (see insert photo), having shed their gills and developed lungs, will adapt to a terrestrial life.

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Promethea Pupae Parasitized

12-21-15 promethea cocoon 257Although a lack of snow makes tracks difficult to find, there are other, more permanent, animal signs such as bird nests and cocoons that are visible this time of year. Among the more obvious is the cocoon of the Promethea Moth – a giant silk moth. When the time for pupating arrives the Promethea caterpillar selects a leaf and strengthens its attachment to the tree by spinning silk around the petiole of the leaf as well as the branch it grows on (to assure that it doesn’t fall off the tree). With more silk it rolls the leaf up into a tube and then proceeds to spin its cocoon inside the rolled-up leaf, leaving a valve-like structure at the top of the cocoon through which the adult moth exits in the spring.

Unfortunately for silk moths, many are parasitized by flies and wasps (there are nearly 100 natural parasites that affect the 24 species of silk moths east of the Mississippi River). Frequently flies or wasps lay their eggs in silk moth caterpillars and then develop inside them. Eventually the fly or wasp larva secretes a substance that causes the caterpillar to pupate, at which time the fly or wasp also pupates and then exits the moth pupa and cocoon (see exit hole in smaller photo), causing the death of the moth pupa. Silk moth populations are decreasing, in part as a result of these parasitoids. Among others, a non-native parasitic tachinid fly, Compsilura concinnata, is wreaking havoc on silk moths.

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