Tuesday, December 18, 2012

Time for larvae

A bluish-grey larva - maybe Monomacra violacea?
6.2mm long
Larva, larvae, funny words.  Now that I have a picture (at least an idea) of how the adult flea beetles spread themselves across the Passionflower plants, it's time to tackle a harder question: what are the flea beetles' larvae eating?  There is a possibility that they are more specialized than the adults, since they not only have to survive out there, but also need to grow from egg to pupa.  Heliconius larvae grow extremely rapidly, quadrupling in size in just a few hours and then moulting, five times in rapid succession.  They grow 1000 times as large in 5-6 days!  They are true "growing machines."  But what about the beetle larvae?  How fast do they grow?  Which plants can they survive on?  How do they behave when feeding?

A yellowish larva - maybe the Red-white Ptocadica?
5.9 mm long
I began a couple of months ago to bring a few larvae from the forest into the laboratory, putting them on leaves similar to the ones they were found on.  The ones raised in containers in the lab did poorly, not feeding well and many dying in a few days.  I then decided to try to raise them on live potted plants in the greenhouse.  Actually we call it a shadehouse here at La Selva, a frame covered with shady mesh allowing the interior to stay cool by allowing free entry of air while creating shade to partially block the rays of the sun.  Just last week some of the Passiflora lobata plants in the shadehouse became large enough to use, and I put two flea beetle larvae on a new leaf.  They soon began feeding and seem to be thriving.

The Red-white Ptocadica adult.
The adults may stay on the shadehouse plants
for a few days.
I want to measure how fast the larvae grow, but they are delicate and should not be handled any more than necessary.  I found out a way to use my camera as a measuring device.  I put the camera on a single, consistent manual focus, and take a sharply focused picture.  All such pictures should have the same field of view (measured in millimeters) from side to side.  By comparing the length of the larvae in the photo to the full width I can then calculate low long the larva is in millimeters.  In this way I can see how fast a larva is growing by taking its picture every day.   I don't need to touch the larva at all.

A shield bug just happened to walk by,
with the brightest orange spots!

This dragonfly has amazing eyes. 
Are the brown parts sunglsses?
Of course I have to take photos of other creatures, such as the cute Red-white Ptocadica beetle, perhaps the parent of one of the larvae shown above.  Not to mention this spectacular brown-eyed dragonfly, er, brown on the top 1/3 of the eye dragonfly.  and the orange-spotted shield bug that happened to walk by.  The riches of nature never cease to amaze!

No comments:

Post a Comment