An online resource based on the award-winning nature guide

July

Green Frogs’ Coloring

7-13-16  turquoise green frog 030Despite their name, Green Frogs are not always green.  They can be brown or tan, as well as many shades of green.  Usually Green Frogs in the Northeast are a combination of these colors, but occasionally one sees greenish-blue coloring on a Green Frog.  An understanding of what causes a frog’s green color sheds light on why sometimes all or part of a Green Frog may be close to turquoise than green.

Basically there are three types of pigment cells (chromatophores) which stack up on top of each other in a frog’s skin.  The bottom layer (melanophores) of pigment cells contain melanin, a pigment that appears dark brown or black.  On top of these cells are iridopores, which reflect light off the surface of crystals inside the cells.  When light hits these cells, they produce a silvery iridescent reflection in frogs, as well as other amphibians, fish and invertebrates. In most green frogs, sunlight penetrates through the skin to the little mirrors in the iridophores. The light that reflects back is blue. The blue light travels up to the top layer of cells called xanthophores, which often contain yellowish pigments. The light that filters through the top cells appears green to the human eye.

The pictured turquoise-headed Green Frog most likely lacks some xanthophores in the skin on its head, and thus we see reflected blue light there.

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Great Spangled Fritillaries Flying, Feeding & Mating

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There are five species of fritillaries in New England: the Great Spangled, Aphrodite, Atlantis, Silver-bordered and Meadow.  The largest and most common is the Great Spangled Fritillary.

The adults are in flight now, feeding on the nectar of a variety of flowers, including Joe-Pye Weed (pictured), mints and milkweed.  In general they prefer long, tubular flowers.  Males patrol open areas for females.  After mating, female Great Spangled Fritillaries enter a resting state called diapause, which they emerge from in late summer.  At this time they lay their eggs near patches of violets (larval host plant) and die. The caterpillars hatch in the fall and overwinter as larvae, becoming active in the spring at the same time as violet plants begin to grow.  Feeding takes place at night, and is limited to violet leaves. Hopefully global warming will not upset the synchronization of these two events.

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Dead Man’s Fingers

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When it first appears above ground in the spring, the club or finger-shaped fruit of Dead Man’s Fingers (Xylaria polymorphaappears powdery white from the asexual spores that cover its surface. As it matures, it acquires a crusty, black surface. This is the sexual stage. The interior of the fruiting body of this fungus is white; just inside the outer surface is a blackened, dotted layer containing structures called perithecia which hold sacs of spores.

Dead Man’s Fingers, unlike most fungi, which release their spores in a few hours or days, releases its spores over months, or even years. It can have many separate fingers, sometimes fused together to resemble a hand.  Look for this fungus growing on hardwood stumps and logs, particularly American beech and maples.

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Butterflies As Pollinators

7-29-16  swallowtail in lily 086Butterflies pollinate during the day while most flowers are open and they have better color perception than bees or even humans, but they are less efficient than bees at moving pollen between plants.  Their legs and proboscis are longer and farther away from the flower’s pollen so they do not pick up as much pollen on their bodies.  They also lack specialized structures for collecting pollen. Nevertheless, it is hard to imagine that some of the Daylily pollen that has collected on this Eastern Tiger Swallowtail’s wings might not fall onto or be brushed against the stigma of the next Daylily it visits.

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Lesser Purple Fringed Orchis Flowering

7-27-16  smaller purple fringed orchis 082

Approximately sixty orchids can be found in the Northeast, more than half of which are found growing in bogs and fens.  (Bogs are filled with atmospheric moisture and have very low levels of nutrients; fens receive their water from streams or springs, and have slightly more nutrients than bogs.)  In July and August in the Northeast,  the Lesser Purple Fringed Orchis (Platanthera psycodes) sends up a  1 – 3’ spike filled with fragrant, tiny (3/4” long) flowers, each of which possesses a three-lobed, fringed lower lip and a long nectar spur .  Found in cooler habitats, its range is being pushed northwards as global temperatures warm — a  specimen was found at an altitude of 1,500 feet in Vermont.   This orchid is on several states’ endangered or threatened lists outside of New England, and a species of special concern in Rhode Island. (Thanks to Shiela and Steven Swett for photo op.)

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Bald Eagle Eyesight

7-26-16  juv. bald eagle2 026The eyesight of a Bald Eagle is impressive.  Part of the reason for their excellent vision is that these birds of prey have two centers of focus (foveae), which allow them to see both forward and to the side at the same time. Cone cells, one of three types of photoreceptor cells in the retina, perceive color, fine detail and rapid movement.  In a human, the fovea has 200,000 cones per millimeter; in the central fovea of a Bald Eagle’s eye, there are about a million cones per millimeter. An eagle’s eye is almost as large as a human’s, but its sharpness is at least four times that of a person with perfect vision.

Bald eagles are capable of seeing fish in the water from several hundred feet above, while soaring, gliding or in flapping flight.  (They locate and catch dead fish much more rapidly and efficiently than live fish, because dead fish float with their light underside up, making them easier to see.)  It is very likely that a Bald Eagle can identify a rabbit moving almost a mile away. This would mean that an eagle flying at an altitude of 1000 feet over open country could spot prey over an area of almost 3 square miles from a fixed position. (photo: recently fledged, juvenile Bald Eagle)

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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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