Singular use of “the young” to mean animal offspring?

The Academy of Natural Sciences at Drexel University has a webpage about butterflies in which I read the following:

Butterflies, moths, beetles, flies and bees have complete metamorphosis. The young (called a larva instead of a nymph) is very different from the adults. It also usually eats different types of food.

In the second sentence above, “the young” is treated as a singular noun. However, Lexico states that in the usage as “offspring” it is treated as plural. So is the usage on the Museum website incorrect?

Summary

The crux of the question is:

Can ‘young’ be used as a singular as well as a plural noun in relation to the offspring of animals?

In, brief, although plural usage is much more common, the answer is YES.

I shall present evidence for my conclusion and then briefly address the problem with the context of the sentence in question.

Evidence for use of ‘young’ as a singular noun

(a) Dictionaries
Some modern internet dictionaries only have entries for ‘young’ as a plural noun. These include Cambridge, Chambers, and Collins. Oxford is equivocal. The online Lexico implies this, but my copy of its parent OED (1928) has the following example of singular usage from 1759:

“The elephant scarcely produces one young in two years”

Furthermore there is unequivocal support for the singular in Merriam–Webster — pertinent to the specific American English example:

2 : a single recently born or hatched animal — (my italics)

(b) Usage in books related to natural history
I conducted ngram searches for “the young is/are” and “the young is/are called”, and examined the results to find ones with the appropriate context. This confirms the greater usage of ‘young’ in the plural, but provided plenty of examples of singular use, some of which I list below. Certainly some are in older texts and those published in the former British Empire, but I also include more modern ones.

“The young is called middle spotted Woodpecker” — Forster (1817)
“He goat. The young is called ἔριφος — Jones (1825)
“The young is called a fetus.” — US Supreme Court (1832)
“the young is entirely white , and covered with a woolly down” — Wood (1882)
“while the young is mottled and very different in appearance…” (1888)
“The young is now more confident in its movements and usually travels around sitting high on the mother’s back” — Martin (1999)
“after the young is returned to the pouch…” — Tyndale-Biscoe (2005)
“For several days, if the young is detached from the nipple…” — Long (2008)

Problems with the context

There are a couple of mitigating circumstances to explain the poster’s aversion to the singular ‘young’ — something that I have argued is incorrect. The general context in which the second two sentences find themselves contain errors or stylistic awkwardness in the use of singular and plural.

First, all references to the adult insects are in the plural — in the completion of the sentence (…different from the adults) and in the preceding sentence. Although it is not ungrammatical to say, e.g. “The child differs from its parents”, the inconsistent usage appears awkward.

Second, as pointed out by @herisson, the web page on which the example is found contains the indefensible: “The young (called a nymph) usually look like small adults but without the wings.”