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Metamorphosis

Monarchs Splitting Exoskeleton For The Fifth And Final Time

In the Northeast there appears to be an amazingly large number of Monarch larvae this year, and most of these larvae will complete their metamorphosis by transforming into a beautiful green chrysalis. Once mature, the larva, or caterpillar, wanders about and finds a suitable spot (usually protected and stable) to spend the next two weeks hanging precariously in the wind.  It then spins a silk mat in this location, and puts a silk “button” in the middle of the mat.  It clasps the button with its last set of prolegs (it has three pairs of true legs, and five pairs of so-called prolegs) and spends about 18 hours hanging in a “J,” with its head down, preparing to split its exoskeleton for the last time and reveal the chrysalis within it.

Ba Rea, a Monarch specialist (and publisher of my children’s book, Milkweed Visitors), informs her “Monarchchaser’s Blog” (https://monarchchaser.wordpress.com/about-monarchs/) readers that even though the visible changes between the larval and pupal (chrysalis) stages of a Monarch are sudden, inside the caterpillar these changes are taking place gradually and long before we can see them.  “The parts that will transform the caterpillar into a butterfly are present from the time that the egg hatches.  Inside the caterpillar are “imaginal disks.”  As wonderfully fanciful as the word imaginal sounds, it is actually referring to the adult stage of the monarch which is called the imago.  These disks are the cells that will become the butterfly’s wings, legs, proboscis and antennae, among other things.  By the time the caterpillar is half an inch long its butterfly wings are already developing inside it.

After eight to fifteen days, the adult Monarch emerges from its chrysalis and heads towards Mexico (butterflies that emerge after the middle of August migrate). It is the great grandchildren and great great grandchildren of these migrating monarchs that will return next summer.  (Photo: Monarch hanging in a “J” from Jewelweed, also known as Touch-Me-Not — not the sturdiest of plants to hang from!)

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Gray Treefrogs Metamorphosing

Gray Treefrogs are often heard but rarely seen, due both to their cryptic coloration as well as the fact that they are arboreal.  They tend to perch (grasping trees with their toes which bear large, adhesive, mucous-secreting disks at their tips) in vegetation surrounding swamps and ponds, where their robust, territorial and mating trilling can be heard (males call between 500-15,000 times per hour). To hear trilling Gray Treefrogs go to https://www.youtube.com/watch?v=CSkhM24Fi-k.

After choosing a mate and mating, Gray Treefrog females lay up to 2,000 eggs which hatch in 2-5 days.  For the next month or two the tadpoles breath with gills and consume vegetation.  Full-sized tadpoles are green or black with red or orange tails.  Towards the end of summer, the tadpoles begin their transformation into frogs, developing limbs and lungs, absorbing their tails and changing from a diet of plants to one of insects.

Adult Gray Treefrogs are mottled gray or green (depending on their surroundings, temperature, and humidity) and have an uncanny resemblance to lichen. Recently-metamorphosed young treefrogs such as the one pictured are a brilliant emerald green.  (Photo: young Gray Treefrog with adult Gray Treefrog inset) (Thanks to Brian Long for photo op.)

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Tadpole Maturation

5-22-19 green heron and tadpole _U1A1148The eggs of Wood Frogs, the earliest species of frog to breed in the Northeast, are just hatching and tiny Wood Frog tadpoles can be found swimming about at this time of year. This Green Heron is devouring a tadpole, but it is anything but tiny – certainly not a Wood Frog tadpole. How can this be?

The answer is that the tadpole that the Green Heron caught did not hatch this spring – it hatched last summer. Unlike Wood Frogs and Spring Peepers that mature in roughly two months, Green Frogs and American Bullfrogs can take two or even three years to metamorphose into adult frogs. By their second summer they are of substantial size. The Green Heron has caught a Green Frog or Bullfrog tadpole that has overwintered and would probably have matured this summer.

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Caddisfly Eggs Hatching

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The Mystery Photo was of a caddisfly’s egg mass which had been deposited on the leaf of a Turtlehead plant that was growing adjacent to the water, so that when the eggs hatch, the larvae will drop straight down into the water. (Congratulations to “bcottam2014,” the first person to correctly identify the Mystery Photo!)

Almost all caddisflies lay their eggs in the water, but in New England there is a family of northern case makers (Limnephilidae) whose members deposit an egg mass above the water on vegetation (see photo). After hatching and dropping into the water, these caddisflies will spend anywhere from two or three months to two years as aquatic larvae and pupae, emerging as adults with about a thirty day lifespan.

While they are larvae, most northern case-making caddisflies have silk glands with which they construct portable cases or attached retreats. Each species of caddisfly builds the same type of case, out of similar material, thus, it is possible to identify the species of caddisfly you’ve encountered from the appearance of its case.  Some species use pebbles, some bits of leaves, some sticks. Vegetative material must be chewed into just the right size and shape pieces. The caddisflies use these cases as a source of camouflage, physical protection and as a means of acquiring food.  When it comes time to pupate, they build cocoons within their cases.

Emergence of adults eventually takes place and for the next month or so they live a terrestrial life.  Like their close relatives, butterflies and moths, adult caddisflies have wings, but they are easily distinguishable from moths and butterflies due to the  tent-like slant the caddisfly holds its wings in when not flying. (Photo:  caddisfly larvae hatching from egg mass; inset – older caddisfly larva inside pebble case it built)

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Ladybugs Maturing & Seeking Shelter

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Ladybugs, along with roughly 88% of all insects, pass through four separate stages (egg, larva, pupa, adult) in their life cycle. This form of maturation is referred to as complete metamorphosis. Like many other insects that experience complete metamorphosis, the larval, pupal and adult stages do not closely resemble one another. While most of us would have no trouble recognizing an adult ladybug, the two middle stages are strikingly different from the adult spotted beetle we’re familiar with. After a ladybug egg hatches, the larva emerges, looking a bit like a tiny alligator. Anywhere from seven to twenty-one days later and after several molts, the larva attaches itself to a leaf and pupates. The pupa assumes yet another bizarre form, which some feel resembles a shrimp. Within a week or two the pupa matures and transforms into an adult ladybug. Most species of ladybugs hibernate (technically enter “diapause,” as it’s referred to with insects) as adults in large groups under leaf litter, logs and other protected spots.


Blue Mud Dauber Wasps Building Nests

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Yesterday’s Mystery Photo showed evidence of a Blue Mud Dauber Wasp (Chalybion californicum) scraping the mud with its mandibles as well as the resulting ball of mud it had formed to use as building material for its nest.  You can get a hint in this photograph of the iridescent blue wings that give this wasp its common name.

Mud dauber is a common name for solitary wasps that make individual nests for their eggs/brood with mud. There are many species of mud daubers, but most are between one and one-and-a-half inches long, black or metallic blue, and typically have a narrowing, or “thread-waist,” between their thorax and abdomen.

Most species of mud daubers, after making a small (1/4” diameter) tube nest out of mud or refurbishing an old nest, leave to forage for spiders. Once a spider has been located, the wasp stings and paralyzes it, but does not kill it (so as to prolong decomposition), carries it back to its nest, and repeats this process over and over until the nest is stuffed with living prey. The wasp then lays an egg in this mass of spiders and seals the nest with mud. The egg hatches and the wasp larva consumes the spiders as it grows. After pupating in the fall, the adult wasp emerges in the spring, mates and the cycle continues.

The reason that the ball of mud that the Blue Mud Dauber had formed was not taken back to the nest site as building material appears to be a small rootlet which anchors the ball to the ground, preventing the wasp from removing it.


Mourning Cloaks Surviving On Sap

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Who doesn’t celebrate at the sight of a Mourning Cloak butterfly gliding through the woods on soft, spring breezes? Because the adults spend the winter hibernating behind loose bark, Mourning Cloaks are among the first butterflies to take flight in the spring. Most butterflies overwinter as eggs or pupae inside chrysalises, and have to complete metamorphosis before they can take to the air.

Surviving in March and April, when there is little, if any, nectar to be found, is challenging. Mourning Cloaks sustain themselves with the sap that exudes from broken tree branches or wounds in tree trunks. Oaks are their preferred source of sap. When they find some, they walk down the trunk to the sap and feed head downward (see photo).

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