Meteorologists define March, April and May as the months of spring in the Northern Hemisphere. Seasonally, spring is a time of birth and renewal.
On the renewal side, plants that have been dormant during the winter sprout new foliage. Some hibernating animals – including a few insects – become active. Birds that fled to southern climes return.
Most of us think of birth as the process associated with the emergence of a new baby mammal from the body of its mother. In a broader sense, birth can be defined as the start of life of a physically separate being. In this sense, hatching of eggs would also be considered birth. By either definition, spring is a time for births. It is a time when a lot of animal species bring new individuals into the world.
In the world of birds, insects and amphibians, a new baby emerges from an egg that is deposited outside of the body of the mother. In both cases the egg is stuffed with enough nutrients to feed the baby during its development prior to hatching.
There is a major difference between the development process of bird and insect eggs. In the bird world, eggs are deposited in one location – a nest – where the adult birds will incubate the eggs. In this process, birds provide the heat necessary for the eggs to hatch.
Consequently, bird eggs almost always hatch in a defined time, according to species. For chicken eggs, incubation time is 21 days. Pekin ducks require 28 days of incubation, the English sparrow 12 days.
On the other hand, insect eggs – with the exception of those of the honeybee – are not incubated and hatch as a result of environmental temperatures. That means the time associated with the hatching of insect eggs varies according to surrounding temperatures. Eggs of the cabbage butterfly, a well-known garden pest, hatch in one to three days. Monarch butterfly eggs hatch in three to five days. In all instances, warmer temperatures mean that the eggs will hatch more quickly.
As it turns out, honeybees, as a colony, incubate their eggs and the newly hatched larvae. By using metabolic heat from their bodies, these insects can keep the brood area of the comb between 92 and 97 degrees F. Perfect temperatures for egg hatching and rapid larval growth. And, amazingly, they can do this in the coldest days of winter!
We all know that bird eggs are oval, have a shell, vary in size depending on species and are sometimes colored with distinct markings. The outer layer of an insect egg is called a chorion and, like shells of bird eggs, varies among species in shape, size and color.
In birds, amphibians and insects, the egg is sort of a halfway house between the body of the mother and the newborn young. Compare that to mammals, where the body of the mother protects the unborn young for a period of time known as pregnancy.
Bird and insect eggs are exposed to a number of predators and parasites between the time the eggs are laid and the time the young hatch. Adult birds try to protect their eggs from predators and also feed and provide warmth to their developing young. Insects, on the other hand, generally just leave their young to survive on their own.
OK, I have to admit it: Parenting skills of insects are somewhat lacking. But one thing that mother insects do for their children is that they try to deposit eggs in or on the food source that their young will eat after they hatch.
For example a cabbage butterfly will lay her eggs on a cabbage plant, a house fly in a garbage heap, a parasitic wasp in the body of a host insect or a predator ladybug near a colony of aphids. In human terms, that would be like giving a newborn child a lifetime gift certificate to a fast-food restaurant!