Planet of the Bugs: Evolution and the Rise of Insects Read Online Free PDF Page A

different niches. You will find different kinds of insects feeding on leaves, boring in stems, mining under leaf surfaces, chewing in flower buds or seed pods, living under bark, or boring deep into the heartwood or below ground into roots. A young beetle may spend its entire immature life living and feeding inside a single tiny plant seed, while the adult can live in a totally different niche.

     
    FIGURE 1.2. Fairyfly wasps (family Mymaridae) are insect-egg parasitoids that occupy minute ecological niches.
Tinkerbella nana
is one of the smallest known flying insects. (Photo by Jennifer Read.)
     
    While many common insects, such as the monarch butterfly, have a wide distribution and a fairly broad niche, the vast majority of insect species are extremely small and have very tiny, often localized niches. The tiniest insects, microscopic “fairyfly” wasps too small to see without magnification, develop inside the single egg of another insect. The specialized narrow niches of parasitic insects are also particularly impressive. There are bird lice that live only in the pouches of pelicans and mammal lice that live only in the fur and nostrils of sea lions. In fact, most different kinds of birds and mammals have specialized lice species living on their bodies, except for bats. But another group of insects has evolved to fill this ecological niche. Remarkably, there are bloodsucking parasitic flies that live in bat fur, so while vampire bats might drink your blood, their own blood is being fed on in turn. In Wyoming and other boreal parts of North America, there is a flightless parasitic beetle species,
Platypsyllus castoris
, the beaver parasite beetle, which lives only in the fur of living beavers.
Neoneurus mantis
,an insect I discovered in Wyoming, is a tiny wasp that develops parasitically inside the abdomens of one species of mound-building
Formica
ant. When I first found them in 1990, they were flying in association with only three particular ant colonies. Over the past two decades, two of those colonies have declined in numbers, and the parasites have disappeared. So over the past several years, I’ve only been able to find this tiny wasp in the nearby mountains in June, at only one particular ant nest.

     
    FIGURE 1.3. Bat flies (family Streblidae) are highly specialized, blood-feeding bat parasites. This one lives on vampire bats at Palo Verde National Park in Costa Rica.
     
    A second reason for their vast diversity is flight, which has allowed winged insects to expand their niches into the air. For as long as 150 million years, insects were the only animals that could fly, and that gave them great advantages in terms of their ability to escape predators and to disperse and colonize new areas. The eventual evolution of winged pterosaurs, birds, and bats didn’t drive insects out of the air. It simply provided the selective forces to drive additional diversification and specialization. But wings are also very useful for things other than flight. Insects are cold-blooded animals, and since blood flows through the veins of their wings, insect wings work very well as little solar panels for warming up on cold mornings. Insect wings are also canvasses for multifarious colors and patterns that play important roles in insect behavior, especially in courtship and mating, and facilitating mate recognition in diverse and complex environments. Wing colors can also enhance survival by either crypsis (camouflage) or aposematism (bright warning coloration).
    Third, but certainly not least, insects have evolved elaborate methods of development, including complex metamorphosis with young developmental forms (larvae) that are stunningly different from adults. That was a remarkable innovation, which allowed adult insects to avoid competing with their own offspring for food. A young insect larva, such as a caterpillar of a butterfly, becomes a feeding machine that can concentrate its activities on eating and growing, often in a