Insects

Dominating the biological spectrum with nearly a million known species, members of Insecta may represent as much as 90% of multicellular life on Earth. Though the incredible diversity of insects overwhelms any attempt at inclusive summarization, adult members of this class can be identified by the following characteristics: three pairs of legs; a segmented body including a head, thorax, and abdomen; and one pair of antennae. Most insects also have compound eyes, a trait exclusive to the phylum Arthropoda to which the class Insecta belongs. Additionally, insects are the only known invertebrates capable of flight, and many species are equipped with one or two pairs of wings. A dizzying array of adaptations, from social behaviors and complex communication to metamorphic cycles and camouflaging mimicry, allow insects to inhabit nearly all environments and persist as one of the most integral aspects of their various ecosystems.

Many people view insects primarily as pests (Berenbaum 1996, Johnson & Triplehorn 2004). Indeed, insects cause tremendous damage to our agricultural crops either by feeding directly on cultivated plants (e. g., locusts, thrips, fruit flies, weevils, leaf beetles, moth larvae) or through the transmission of plant viruses, bacterial, and fungal diseases (e. g., aphids, whiteflies, leafhoppers). They also invade our homes (e. g., cockroaches, silverfish, house flies), infest stored products (e. g., clothes moths, flour moths, rice weevils, dermestid beetles), and destroy our buildings (e. g., termites, wood-boring beetles). Some insects parasitize humans and livestock (e. g., lice, bed bugs, bot flies), and some of these parasites are important vectors of disease (e. g., mosquitos, tsetse flies, black flies, kissing bugs, fleas). A few insects also pose a health threat because of their venom (e. g., bees and wasps, blister beetles, stinging caterpillars).

Insects pollinate many of our crops, such as most orchard fruits, vegetables, and clover, which is an important livestock feed. Approximately a third of our food production depends on pollinator services, with insects, and particularly bees, doing most of the work (Buchmann & Nabham 1996, Free 1993, Ghazoul 2005, Klein et al. 2007). Most of the other direct services provided by insects are of relatively minor significance. While many people enjoy the honey produced by bee colonies, the use of insects themselves as food (entomophagy) is rather limited in humans (DeFoliart 1999, Menzel & D'Aluisio. 1998). Other insect products like lacquer and dyes from scale insects, beeswax, and silk from moth larvae support major industries, but none of these materials are essential to human welfare.

By far the most important benefits of insects to human societies are due to the ways they shape the world around us (Schowalter 2000, Waldbauer 2003). Without insects, most of our landscapes would look very different and would be much less hospitable to us and many other organisms. As herbivores, pollinators, and seed dispersers, insects have had an immense impact on the adaptive radiation of plants, particularly angiosperms (Grimaldi & Engel 2005). Their activities control many contemporary plant populations and affect the phenology and resource allocation of plants, thereby influencing the composition of plant communities (Weisser & Siemann 2000). Insects also participate in the decomposition of organic materials and thus facilitate the recycling of carbon, nitrogen, and other nutrients (Wardle 2002). In their absence, dung, carrion, dead wood, and leaf litter would accummulate in many terrestrial and aquatic environments. Many animals, including most vertebrates and spiders, rely heavily on insects in their diets, and as predators, parasitoids, and vectors of disease, insects control the populations of other animals (Thompson & Althoff 1999).

In this episode, we travel to Costa Rica to experience firsthand the astonishing variety of insect life in this tiny Central American nation—20,000 different kinds of butterflies and moths alone!

José Montero and Manuel Zumbado, both of the Costa Rican National Biodiversity Institute, INBio, explain how this crossroads between North and South America became a hotspot for evolutionary innovation, producing such spectacular specimens as Thysania agrippina, a moth so large that it’s often mistaken for….well, you’ll have to listen to find out!

Listen to the podcast on the Learning + Education section of EOL.