Ladybug life-cycle – Interior Alaska

Last year I saw ladybugs on occasion but did not pay attention to them very much. This spring I noticed that they were one of the first insects to appear, crawling up and down the birch tree trunks, some while there was still snow on the ground below. Knowing they could not have hatched and grown to that size so soon after winter I realized that they must be overwintering.

Insects in Alaska that over winter have to deal with some incredible temperature changes. They must be able to freeze and thaw without dying which is a feat in itself. Many incorporate a natural antifreeze that keeps their cells from bursting and being damaged by ice crystal formation.

Soon after the snow melted and I started seeing the ladybugs I also started to see clusters of yellow eggs on the birch tree trunks. It took me a little while to figure out that the ladybugs were laying them.

It took me several weeks more before I discovered ladybugs mating and then finally a ladybug laying eggs.

After the flurry of egg laying, the adults that overwintered mostly disappeared. The numbers I’d seen early in the spring were gone. I don’t know if they died or moved up into the tree tops, but all that was left on the trunks were the eggs. I watched the eggs expecting to see changes but I think I missed them. I was really hoping to find some hatching but I missed this stage. I’ll have to look again next year.

A few weeks after the eggs were laid I started to see very small larva. Basically black worm like creatures. The larva started out microscopic, a millimeter in length and grew over the course of several weeks to be between 1-2 cm long and then 2-3 cm in some cases.

During this growth period they moved fairly quickly. Although I’m sure they were everywhere, I mostly observed them on the trunks of birch trees. Birch trees have smooth white bark that makes spotting insects easy.

After several weeks of growth, I noticed the larva slowing down and eventually I started finding them with the back of their abdomen stuck to the surface of the tree trunks. I wasn’t sure what was going on at first, but soon realize that rather than build a cocoon like caterpillars, they simply anchored their bodies to the tree and metamorphosed within their own skin crating a pupae within their own exoskeleton. The larvae were in many cases longer and skinnier than the adults they would become. As I observed the pupa, they slowly changed shape, contracting lengthwise and expanding in diameter to accommodate the changes occurring within.

It has now been several weeks since they started pupating and today I started noticing empty pupae cases and fresh looking ladybugs crawling on the trees. I started looking closely and lucked out when I found a ladybug that had just hatched.

Much like butterflies and dragonflies, a newly hatched ladybug is pale in color and soft. It’s exoskeleton and wings have yet to harden and set. The one I found today was white and black, although I could see the faint markings of spots that I’m sure within a few hours would have darkened as the exoskeleton hardened.

At this point I don’t know if they will try to have another cycle before winter or if this batch that has just hatched will be the ones that overwinter. I will continue to observe them this summer to see.