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Archive for July, 2011

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.


Decomposition

It’s a well-known fact that fungi, along with invertebrates and bacteria, are responsible for the majority of plant and animal decomposition that occurs.  They are very efficient at breaking down organic material into simpler forms of matter that can then be recycled.  Seeing  this mushroom, the fruiting body of a fungus, undergoing  the same process  with which it is associated reminds me of the porcupine with a face full of quills it received from its relative.


Rattlesnake Plantains

Rattlesnake plantains get their name from their rosette of broad, egg-shaped leaves, which are similar in shape to those of plantain, a common lawn weed. Although they are called plantains, they are actually orchids.  There are four species of rattlesnake plantains in New England, and the differences between them are subtle.  The pictured checkered rattlesnake plantain (Goodyera tesselata) has leaves with soft green markings, whereas the other three species have silver-white central stripes and/or markings.  Sometimes the species hybridize, making identification challenging.

 


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.