Life History
Last Review/Updated: May 31, 2002
Invertebrates
grow from egg to adult in three basic ways. Some develop in a continuous
process without interruption — for example, snails and clams. In this
case the young look like the adults they will become as they undergo
a steady increase in size. Others undergo a process involving a series
of rapid growth periods which occur after each moulting or skin shedding — for
example, grasshoppers and spiders. A third group undergo a growth process
involving four completely different stages (egg, larva, pupa, and adult).
This group includes flies, butterflies and beetles.
Though
some invertebrates lay only a few eggs, others produce millions. Most
invertebrates live only a few weeks to a year or two, but some may
reach 100 years or more.
Many invertebrates scatter or disperse by travelling with the wind. Mosquitoes and blackflies can travel 30 km (20 mi.) per day in this manner. Spiders may cover a distance of more than 50 km (30 mi.) per day by creating a balloon-like "sail" from the silk they use to spin their webs. Invertebrates that live in streams are often carried long distances by water currents.
