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Crustacean Deduction

9-18-17 crustacean 049A5188Arthropods are invertebrates possessing an exoskeleton, a segmented body and paired jointed legs. Crustaceans make up one group of arthropods. Insects, spiders, ticks, mites, crabs, lobsters, woodlice, centipedes and millipedes are all crustaceans. Underneath a rotting log I recently discovered a crustacean resting right next to a clump of eggs. Not wanting to disturb the creature, I hazarded a guess as to its identity from what I could see. Its form narrowed it down to either a woodlouse (also known as sow bug, pill bug and roly-poly), centipede or millipede. Most centipedes have one pair of legs per body segment, eliminating them from the field of possibilities, for the photographed crustacean has two legs per body segment, as do millipedes and woodlice.

The next clue had to do with the eggs, which I presumed were produced by the creature right next to them. Woodlice have a “marsupium,” a chamber under the thorax which is filled with water in which their (often several hundred) eggs are brooded. Millipedes, on the other hand, lay from ten to three hundred eggs at a time, and deposit them on moist soil. In some species an adult remains to guard the eggs.

I cannot categorically say that today’s subject is a millipede and its eggs, but all signs point to it. If there is a crustacean expert among Naturally Curious readers, please confirm or correct my deduced identification!


Hover Fly Mimics Bald-faced Hornet

8-5-15 bald-faced hornet and hover flyAdult hover flies, often referred to as syrphid (family Syrphidae) or flower flies, feed on pollen and nectar, and are often seen hovering at or crawling on flowers. Many have black and yellow bands on their abdomen, and are frequently mistaken for bees. There are certain species of hover flies that mimic stinging wasps, including yellow jackets and bald-faced hornets (see photo). Predators such as birds, ambush bugs, and spiders might think twice about eating an insect that can sting, and hover flies take advantage of this. The process through which this occurs is called Batesian mimicry, and refers to when a harmless species evolves to imitate a harmful species that has the some of the same predators.

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Eyed Click Beetle

7-10-14 eyed click beetle 789Although this Eyed Click Beetle (Alaus oculatus) looks ferocious with its large, black “eyespots” (actual eyes are below antennae), it is harmless to humans. Like all members of the click beetle, or Elateridae, family, it gets its name from the sound it makes when it flips itself upright. Click beetles possess a spine-like structure as well as a notch under their thorax. When they release the spine from the notch, it snaps and they are propelled into the air. Click beetles use this mechanism to right themselves if they are on their backs. Entomologists feel predators are deterred not only by the false eyes, but by this action. The larvae, called wireworms, spend most of their life (2 to 5 years) in the soil feeding on decaying plants and other insects in the soil before emerging as adults. (Thanks to Liz Ambros for photo op.)

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Goldenrod Spindle Gall

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There are three fairly well-known galls (abnormal plant growths caused by a variety of organisms) on goldenrod – the goldenrod ball gall (round swelling in stem caused by a gall fly), the goldenrod bunch gall (leaves at top of plant are bunched up into a mass caused by a gall midge) and the goldenrod spindle gall (elliptical stem swelling caused by a moth).  The amazing thing about insect galls is that not only do they provide shelter for the insect, but they are nutritious and serve as the insect’s food supply as well.    The spindle-shaped galls are home to the larval stage of the goldenrod gall moth (Gnorimoschema gallaesolidaginis).  In the late fall the adult female moth lays an egg on a low goldenrod leaf, where it overwinters. The larva, or caterpillar, hatches out the following spring and makes its way from the now dead leaf to a newly sprouted goldenrod, where it eats its way through a bud and into the stem.  The goldenrod plant reacts to this activity by forming an elliptical swelling, or gall, around the area where the larva took up residence. The larva feeds and develops all summer.  Prior to pupating, it chews a tunnel all the way through the gall (this is the only stage in which the moth has chewing mouthparts), and then spins a silk cover for it.  The larva then returns to the cavity in the middle of the gall and pupates.  In the fall the adult moth crawls down the tunnel,  bursts through the thin layer of silk and then mates and lays eggs.

Winter Crane Fly

Earlier this week, when temperatures were in the 40’s and the sun was shining in the late afternoon, there were clusters of male winter crane flies (Trichocera sp.) hovering two or three feet above the snow, bobbing up and down as they did their mating dance. Females are on the surface of the snow most of the time, but join a swarm in order to find a mate. Winter crane flies are active throughout the winter, as their name implies, and are a source of food for resident songbirds.  The larvae feed on decaying vegetation, and can be found in leaf litter, shelf fungi and compost heaps.

Cecropia Moth Caterpillar Molting

The caterpillar, or larval, stage of a butterfly or moth is the only stage in which the insect has chewing mouth parts.  Hence, it is the stage during which a great deal of eating takes place.  As the caterpillar eats, it grows larger, and eventually molts its skin, revealing a new, larger skin underneath the old.  A cecropia caterpillar molts four times before spinning its cocoon and pupating. The cecropia caterpillar in this photograph has just molted its skin, which is attached to the plant just above the caterpillar’s head. If you look closely, you can see where the colored tubercles were.  Within an hour of when this photograph was taken, the caterpillar had eaten its skin.


Monarch Caterpillar’s Spinneret

Unlike spiders, whose spinnerets, or silk-spinning  spigots, are located at the tips of their abdomens, caterpillars’ spinnerets are located underneath their heads.  The most prominent white structure with a black band around it is the monarch caterpillar’s spinneret, in which its silk glands are located.  The smaller structures are called maxillary palps and are antennae-like sensory devices.  Prior to metamorphosing into a chrysalis/pupa, the monarch caterpillar draws silk through its spinneret, and forms a small, well-anchored button of silk. The caterpillar clasps this button with a structure called a cremaster, located at the tip of its abdomen, from which it suspends itself upside down.  Soon thereafter its skin splits, revealing a gold-dotted, green chrysalis from which an adult monarch butterfly will emerge in two weeks.