June 6, 2008
A Harlequin's life story
I recently took a batch of Harlequin eggs to the lab and watched them go through their life cycle, so here's a short photo essay depicting the transition from eggs through 4 larval instars, prepupa and pupa to adult ladybird. In the process I discovered that the same camera I use for digiscoping can also be used with a hand lens or microscope (digimicroscoping?) for some extreme close-up images.
Adult Harlequins lay their eggs close to aphid colonies, so that the newly-emerged larvae will have something to feed on. The eggs are laid in batches, often on the underside of a leaf or branch.
Once hatched, the larvae will eat any leftovers or unhatched eggs.
At this stage the larvae are often dwarfed by adult aphids, their preferred prey.
Provided they find enough food, the larvae grow quickly. In this rather gruesome photo, a larva is attacking an aphid while she gives birth to her daughters - the dark dots inside of her body are the eyes of the youngsters. You can also see the spines along the length of the larva's body - these help defend it from being eaten by predators. If food is scarce, the larvae will resort to cannibalism.
When they have eaten enough to outgrow their old skin, they shed it (this process is called ecdysis). They undergo three such moults before pupating.
After each successive moult, the larvae get bigger and start to obtain their war paint. The orange stripes are a clear warning signal to predators that they are not good to eat.
Just after ecdysis, parts of the larva are a gooey pale yellow before hardening to a darker colour.
In the fourth larval instar, Harlequin larvae usually have four yellow spots forming a square on their back.
Before pupating, the larva swells...
... and the yellow-orange pupa emerges.
The pupal case hardens and becomes orange with black markings, much like an adult ladybird.
After a few more days, the adult starts to emerge...
... and finally an adult Harlequin appears. As it gets older, the spots often become larger and more numerous, and the ground colour darker.
These adults will feed, breed, and overwinter (often in people's houses), and the whole process starts over in the following spring.
Posted by rjhall at June 6, 2008 5:46 PM