However, there's one problem: the site uses the word "bug" to describe everything on their site. When I originally wrote this post (back in August), their homepage used the word "bug" at least 67 times, yet only three of the organisms pictured on their homepage were actually bugs.
The problem with the word bug is that while in colloquial English it is typically used to mean something like "any creepy-crawly invertebrate animal I don't like", entomologically speaking the word bug refers only to a specific sub-group of insects, hemipterans.
To understand what hemipterans (true bugs) are, let's review some animal taxonomy. First, animals can be differentiated into a number of phyla (of which the following are just a few):
- Phylum Cnidaria - sea anemones, jellies, etc.
- Phylum Annelida - segmented worms, e.g. leeches, earthworms
- Phylum Arthropoda - animals with a hardened exoskeleton and jointed appendages, e.g. crustaceans, spiders, insects
- Phylum Echinodermata - sea stars, sea urchins, etc.
- Phylum Chordata - tunicates, mammals, reptiles, amphibians, etc.
Invertebrates are vastly more diverse than vertebrates: there are more than 30 invertebrate phyla of animals, and more than a million named species. However, one lineage of invertebrates contains most of their terrestrial diversity: phylum Arthropoda (arthropods). This one phylum contains a majority of the known species of organisms in the world (see the end of this post for more information), and can be broken up taxonomically into four major subgroups on the basis of anatomical differences:
- Chelicerates - spiders, scorpions, etc.
- Myriapods - centipedes and millipedes
- Crustaceans - barnacles, isopods (e.g., pill bugs), decapod crustaceans (e.g., lobster, shrimp, crab ... all the tasty ones), water fleas (e.g., Daphnia)
- Hexapods - primarily including insects, such as grasshoppers, butterflies, flies, bees and wasps, ants, bugs, etc.
Insects are incredibly diverse (with more than 750,000 named species), and can be further broken up into a number of distinct lineages (taxonomic orders). Here are a few of the orders in class Insecta:
- Order Lepidoptera - butterflies and moths
- Order Hymenoptera - bees, wasps, and ants
- Order Orthoptera - grasshoppers and crickets
- Order Coleoptera - beetles (the most diverse group of insects)
- Order Diptera - flies
- Order Isoptera - termites
- Order Siphonaptera - fleas
- Order Odonata - dragonflies and damselflies
- Order Mantodea - mantids (praying mantises)
- Order Hemiptera - true bugs
But what are hemipterans? Hemipterans all have piercing mouthparts that they use to feed on either animal or plant fluids, and some can transmit human diseases (e.g., Chagas disease). Hemipterans also generally exhibit hemimetabolous metamorphosis, meaning that they do not have a distinct larval stage like caterpillars/butterflies; instead, juvenile hemipterans look just like small versions of adult hemipterans (as do juvenile grasshoppers and crickets).
Hemipterans can be grouped into two suborders: Heteroptera and Homoptera. The group of heteropterans people are most likely to know are water striders, though the suborder does contain many other lineages, such as toad bugs, creeping water bugs, giant water bugs, waterscorpions, backswimmers, damsel bugs, minute pirate bugs (most certainly Pharyngula's favorite insects), lace bugs, stink bugs, assassin bugs, ambush bugs, and yes, even bed bugs.
Readers are probably more familiar with homopterans, as that suborder includes cicadas, aphids, whiteflies, leafhoppers, scale insects, and spittlebugs.
So, next time you see an invertebrate flying around the house, think twice before screaming out, "Oh no! It's a bug!"
Bland, Roger G. 1978. How to know the insects. McGraw-Hill.