For the now-abandoned mammal taxon, seeInsectivora.
Thisaardwolf skull exhibits greatly reducedmolars andcarnassials teeth as they are unnecessary for any large, insectivorous animal subsisting on soft insects such astermites. Thedentition of ashrew is very different. The aardwolf uses itscanine teeth in self-defence; accordingly, they have not been greatly reduced.Arobber fly eating ahoverflyThegiant anteater, a large insectivorous mammal
The first vertebrate insectivores wereamphibians. When theyevolved 400 million years ago, the first amphibians werepiscivores, with numerous sharp conical teeth, much like a moderncrocodile. The same tooth arrangement is however also suited for eating animals withexoskeletons, thus the ability to eat insects can stem from piscivory.[3]
At one time, insectivorousmammals werescientifically classified in anorder calledInsectivora. This order is now abandoned, as not all insectivorous mammals are closely related. Most of the Insectivorataxa have been reclassified; those that have not yet been reclassified and found to be truly related to each other remain in the orderEulipotyphla.
Although individually small, insects exist in enormous numbers. Insects make up a very large part of the animal biomass in almost all non-marine, non-polar environments. It has been estimated that the global insect biomass is in the region of 1012 kg (onebillion tons) with an estimatedpopulation of 1018 (one billion billion, orquintillion) organisms.[4]: 13 Many creatures depend on insects for their primary diet, and many that do not (and are thus not technically insectivores) nevertheless use insects as aprotein supplement, particularly when they are breeding.[5]
Insectivorous plants are plants that derive some of theirnutrients from trapping and consuming animals orprotozoan. The benefit they derive from their catch varies considerably; in some species, it might include a small part of their nutrient intake and in others it might be an indispensable source of nutrients. As a rule, however, such animal food, however valuable it might be as a source of certain critically important minerals, is not the plants' major source ofenergy, which they generally derive mainly from photosynthesis.[12]: 14
Insectivorous plants might consume insects and other animal material trapped adventitiously. However, most species to which such food represents an important part of their intake are specifically, often spectacularly, adapted to attract and secure adequate supplies. Their prey animals typically, but not exclusively, compriseinsects and otherarthropods. Plants highly adapted to reliance on animal food use a variety of mechanisms to secure their prey, such as pitfalls, sticky surfaces, hair-trigger snaps, bladder-traps, entangling furriness, and lobster-pot trap mechanisms.[12]: 14–17 Also known ascarnivorous plants, they appear adapted to grow in places where the soil is thin or poor in nutrients, especiallynitrogen, such as acidicbogs and rock outcroppings.[12]: 13
Insectivorous plants include theVenus flytrap, several types ofpitcher plants,butterworts,sundews,bladderworts, thewaterwheel plant,brocchinia and many members of theBromeliaceae. The list is far from complete, and some plants, such asRoridula species, exploit the prey organisms mainly in a mutualistic relationship with other creatures, such as resident organisms that contribute to the digestion of prey. In particular, animal prey organisms supply carnivorous plants with nitrogen, but they also are important sources of various other soluble minerals, such as potassium and trace elements that are in short supply in environments where the plants flourish. This gives them a decisive advantage over other plants, whereas in nutrient-rich soils they tend to be out-competed by plants adapted to aggressive growth where nutrient supplies are not the major constraints.
Technically these plants are not strictly insectivorous, as they consume any animal that they can secure and consume; the distinction is trivial, however, because not many primarily insectivorous organisms exclusively consume insects. Most of those that do have such a restrictive diet, such as certainparasitoids andhunting wasps, are specialized to exploit particular species, not insects in general. Indeed, much as large mantids and spiders will do, the larger varieties of pitcher plants have been known to consumevertebrates such as small rodents and lizards.[12]: 13 Charles Darwin wrote thefirst well-known treatise on carnivorous plants in 1875.[13]