Sunday, 20 January 2013

The Tortoise Beetle - Amazing Metallic Arthropods

They look almost manufactured.   Many tortoise beetles have transparent cuticles, the tough but flexible outer covering which gives the insect family its name protects the delicate creature within.  The living tissue is often metallic in color and can in some species even change color.  The combination is as diverse as it is extraordinary – many look like tiny robots assembled to infiltrate, the ultimate bug. Take a look in at the amazing variations of tortoise beetle our world holds.

Perhaps the most familiar species to our sharp eyed American reader is the Golden Tortoise Beetle (Charidotella sexpunctata) which are common on the North American continent.  Their favorite food by far is the Morning Glory, the flower which unravels in to bloom in the morning and curls up in the evening.   So next time you see these flowers, take a look – although this particular bug is something of a master of disguise.

They have the ability to change color so you may be attracted to their glint, initially.  In fact they almost look like ladybugs which have had a lick of gold paint.  Yet they have tiny valves which control the levels of moisture under their cuticle and so can vary in color, with a swathe of red or black spots.  This ability to change appearance led, over the years, to a number of names being given to the same species.

What comes in gold invariably comes in silver too.  This amazing silver tortoise beetle was photographed in the Kibale forest of Uganda.

The Holy Cross Tortoise Beetle (Aspidomorpha sanctaecrucis) is found in Java and surrounding areas.  Like all tortoise beetles they can pull their cuticle down on to the surface of the leaf which (hopefully for them) seals them off from any unwanted attention from predators.  They get their name because from directly above they look as if they have been crucified.

Of course, the propagation of the species is of utmost importance.

The green and black tortoise beetle from Sumatra in Indonesia also has spectacular colorings.  Like most of the species here it is tiny, around half a centimeter in length.  Yet what it lacks in size it makes up in gorgeous iridescence controlled, like all other tortoise beetle species, through its control of moisture through its body.

Close up, the colors are amazing.

The mottled tortoise beetle (Deloyala guttata) above occurs in all arable parts of the US and Canada. The golden species however, is most common from the Rocky Mountains eastward. In the US they overwinter as adults in leaf litter or in any dry places which afford protection they can find.

Female tortoise beetles lay on average between 15 – 30 eggs underneath leaves.  Around ten days later the larvae appear and go in to a feeding frenzy lasting up to three weeks when they pupate.  Pupation takes around a week and after that the adult emerges. When the conditions are optimum there can be as many as three or four generations in a single year.

We have only touched on a few species of tortoise beetle here – there are around 150 more (and some, no doubt, to still be discovered).  Most do not appear as the select few shown here, but are nonetheless often extraordinary in their own right. Yet the metallic, manufactured looking tortoise beetle species are, unsurprisingly, a favorite of entomologists the world over.

First Image Credit Flickr User Rusty Blackbird

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