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Insects

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.


Monarch Butterfly

This 15-minute-old monarch butterfly that emerged yesterday will live for 2 to 5 weeks, long enough to mate and produce the next generation of monarchs.  The generation of monarchs that emerges a month or more from now will live six to nine months, and not mate until next March or so – after flying  to one of about a dozen locations in the Transvolcanic Mountains of central Mexico (a flight of up to 3,000 miles) and spending  the winter.  Late summer-emerging monarchs live longer than monarchs that emerge earlier in the summer because they do not immediately expend energy on breeding and the cool winter temperature in Mexico slows their metabolism, allowing them a longer life.

 


Cecropia Moth Caterpillar

The larval stage of the Cecropia Moth ( Hyalophora cecropia), a giant silk moth, is a sight to behold.  The yellow, blue and red knobs that adorn its 4″ pale green body are striking.  Look for this caterpillar on apple, ash, box elder, cherry, lilac , birch, maple and poplar trees, whose leaves it consumes with relish.  The larva spins a brown, spindle-shaped, 3” cocoon in the fall, and overwinters as a pupa inside it.  In the spring, the adult Cecropia Moth , North America’s largest native moth, emerges.  Brown, with a 4” to 5” wingspread, it has no mouthparts, and lives only about a week to ten days, during which time the males mate numerous times, and the females lay eggs. Unfortunately, this species of moth seems to be declining in number, in part because it suffers from parasitism by a fly that was introduced to control the Gypsy Moth.

 


Dragonflies and Temperature Control

Often on hot, sunny days you will see dragonflies perched facing away from the sun, with their abdomens raised high in the air above them.  This position actually has a name – the obelisk posture – and some dragonflies and damselflies assume this position to prevent overheating.  They raise their abdomen  until its tip points at the sun, minimizing the surface area exposed to it.  The name given this posture comes from the fact that when the sun is directly overhead, the vertical alignment of the insect’s body suggests an obelisk. The meadowhawk dragonfly in the photograph  assumed  the obelisk posture several seconds after the sun came out from behind  the clouds.  As soon as the sun was obscured by clouds again, the dragonfly would lower its abdomen to a horizontal position. It continued doing this for a considerable amount of time.  Sometimes abdomens are raised for reasons other than temperature control, including threat displays during conflicts.


Leafhoppers

Leafhoppers belong to the family Cicadellidae — one of the largest families of plant-feeding insects.  There are more leafhopper species worldwide than all species of birds, mammals, reptiles, and amphibians combined.  Certain species, including the pictured red-banded leafhopper,Graphocephala coccinea, drink the watery sap from the plant’s xylem tissue, and secrete honeydew, a sugar-rich solution which ants love.  The ants protect the leafhoppers against predators in return for this sweet treat (an arrangement they also have with aphids).


Dragonflies Mating

7-19-11  Mating Dragonflies

Dragonflies (and damselflies) form what is called a “mating wheel” when they mate.  The male (top) grasps the female at the back of her head with the appendages at the tip of his abdomen. The female then curls her abdomen forward so that its tip reaches his sex organs and receives his sperm.  After mating, the male may continue to grasp the female and accompany her while she lays her eggs, to prevent another male from removing his sperm from the female and then mating with her.

 


Robber Flies

Robber flies often perch on the leaves or stems of low plants waiting until suitable prey flies by, and then attack it in the air.  They have long, strong, spiny legs for grabbing prey, and piercing-sucking mouthparts for consuming it.  Robber flies prey on a variety of insects, including bees, beetles, bugs, dragonflies, grasshoppers, flies, leafhoppers and wasps. Once they capture an insect, they pierce it with their short, strong proboscis, or mouthpart, and inject  their saliva into it.  The saliva of robber flies contains enzymes that paralyze the insect and digest its insides, which the robber fly then drinks. The pictured robber fly is feasting on the innards of a stink bug it just captured.


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