Monday, January 27, 2014

The vanishing act

The monarchs were not alone in facing danger in the garden this winter.  On the papaya, there were signs that Alope sphinx moth (Erinnyis alope) caterpillars had been chewing on the edges of the leaves.  However, the caterpillars themselves were nowhere to be seen.  These caterpillars can be well camouflaged against papaya leaf veins, but in this case the caterpillars were not simply disguised.  The caterpillars were gone, and in their place, something else was lined up along the leaf veins.

A ball of white fuzz along a papaya leaf vein.
On several of the papaya leaves, there were fuzzy white objects.  Although the objects were roughly cocoon shaped, they were obviously not the cocoons of the sphinx moths (which pupate on the ground).  Looking from another angle, I could tell that the white fuzz was hollow inside -- just as if it had been made around a caterpillar.

The hollow center of the white fuzz.
Indeed, it looked that way because it had been shaped around a caterpillar.  Parasitic wasp larvae had eaten the caterpillar and then spun their own cocoons within a fuzzy matrix around the quickly disappearing remains of their host.  In a previous year, we kept some of this white fuzz in a jar to find out what was inside; the result was a jar full of tiny black wasps!

Explore some more: Erinnyis alope life cycle

Friday, January 10, 2014

The fallen monarchs

Last winter, we found a monarch chrysalis that had fallen to the ground.  We brought it inside and several days later the story ended happily as the monarch successfully emerged and took flight.  This winter, falling was still a danger -- my mother found two chrysalises on the ground -- but there were also more serious threats lurking in the garden.

The remains of a caterpillar that had begun to form a chrysalis.
When I arrived in Florida and surveyed the garden, the only monarchs that I found were a caterpillar that had died while metamorphosing into a chrysalis (possibly due to disease or parasitism) and a chrysalis that did not look much healthier.

Something seems to have gone wrong for this monarch chrysalis.
The chrysalis was a dark brown color instead of bright green.  Although a healthy monarch chrysalis should turn dark shortly before the butterfly emerges (see here), something was wrong in this case -- the monarch's wing pattern was not visible.

A few days later, the chrysalis was still intact... but empty.
After a few days, the chrysalis was hollow with no obvious sign of what had happened to the butterfly that had been developing inside.  Meanwhile the chrysalises that my mother had rescued from the ground were also brown and hollow.  What had happened to all the monarchs? 

Pupae (left) from the flies that parasitized this monarch chrysalis (right).
Looking in the container below the rescued chrysalises, we found several pupae. These pupae belonged to flies -- flies that had parasitized the chrysalises and then emerged instead of the butterflies.  Unfortunately, since the container was not sealed, the adult flies had already escaped.

Wednesday, January 1, 2014

Out of the old and into the new

Today, millions of New Year's resolutions are going into effect, including many for a new image to go with the new year.  On New Year's Eve, the spider pictured below was also preparing to make changes in the new year.  The spider began its extreme New Year's makeover by dropping out of its old exoskeleton and emerging with a fresh new exoskeleton. 

An orchard orbweaver spider (Leucauge venusta) that had just molted.
However, rather than hoping to lose weight, the spider was preparing to increase in size.  Since the exoskeleton is relatively inflexible, a spider must shed its old exoskeleton and replace it with a roomier one in order to continue to grow.

The spider hanging below its old exoskeleton.