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Posts tagged “Insect

Dragonfly Eclosion – Emergence of Adult

8-4-11 Dragonfly  Eclosion – Emergence of Adult

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At the end of its larval stage, a dragonfly larva crawls out of the water where it’s been living and climbs up onto emergent vegetation, or a nearby rock, where it clings as its skin splits along its back and head.  The adult winged dragonfly pulls itself out of its larval skin through this hole, and grasps the skin (or vegetation or rock) while it pumps its body full of air and sends fluid into its wing veins.  This fluid causes the wings to enlarge — the wing expansion that is evident in these two photographs took place in less than ten minutes.  When it first emerges from its skin, a dragonfly is pale and soft, and the wings have a characteristic pearlescent sheen, as in these photographs.  Within a day or so the wings lose this sheen, the body hardens and colors start to develop.


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.