True anteaters, in the strictest sense, are both few and extremely aberrant

(writing in progress)

Everyone knows that various animals are 'anteaters', viz. specialised for a diet of ants (Hymenoptera: Formicidae, https://en.wikipedia.org/wiki/Ant). These include mammals both placental and metatherian, birds (e.g. terrestrial woodpeckers), snakes (e.g. Typhlopidae), and various invertebrates (e.g. mygalomorph spiders), including certain species of ants themselves, predating other ants.

However, the loose use of the term 'anteater' hides a noteworthy biological pattern and principle.

This is that

extremely few animals actually eat the imagos of ants as their main diets, and
those that do are extremely aberrant in body-form and function, possibly owing to the energy-poverty of this food.

The confusion/obfuscation has arisen at several levels.

Firstly, 'anteaters' usually eat termites - which are completely unrelated to ants because the belong to the order Isoptera, not Hymenoptera - as well as ants.

Although termites, like ants, constitute energy-poor food, they allow a dietary diversification that hypothetically makes all the difference for the survival of 'anteaters'.

So, we can narrow our search-image to those animals in which the diet consists mainly of ants in the narrow/strict sense, viz. Formicidae.

Secondly, even 'true anteaters' usually rely on the eggs, larvae, and/or alates (https://en.wikipedia.org/wiki/Alate) of ants, rather than just the imagos (https://en.wikipedia.org/wiki/Imago). These 'reproductives' tend to be relatively rich as food for animals predating ants, because they tend to be relatively rich in lipid (https://en.wikipedia.org/wiki/Lipid), and relatively free of fibre (chitin, https://en.wikipedia.org/wiki/Chitin) and toxins.

Thus, what is not generally appreciated is that

specialised ant-eaters have aberrant (peculiar/odd, https://www.merriam-webster.com/thesaurus/aberrant) body-forms and ways of life, and
this aberrational pattern can logically be related to the energetic and biochemical limitations that are peculiar to ants as food for insect-eating animals.

The basic idea is that

the imagos of ants, although tending to be common in many environments, present a marginal proposition in terms of digestible energy,
this is because the bodies of the imagos tend to have much structural fibre relative to their content of lipid, and also tend to contain toxic substances such as formic acid (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728552/#:~:text=Ant%20venoms%20have%20been%20found,19%2C20%2C21%5D.), which require energy for their detoxification.

Among birds, the only true anteaters are