2934 THE ZooLoGisT—FEBRUARY, 1872. 
Ryder Street, St. James's, 
April 25th, 1840, 
Dear Sir, 
Having now a vacant half-hour, I devote it to answering 
your letter, received on the 20th inst., on the subject of the British 
species of the genus Lestris. Of these we have four: No. 1, 
the largest (the skua), too well known to require further remark ; 
No. 2 (L. pomerinus), next in size. This is a rare bird in its 
adult state, when in colour it resembles the drawing you sent me; 
in its first autumn it is of the same colour as Bewick’s black-toed 
gull. Mr. Eyton, in his ‘Rarer British Birds, at page 53, has 
figured the pomerinus in change—to the light-coloured plumage ; 
when adult, the two tail-feathers are elongated, but not to the 
extent found in the smaller-sized species. 
The confusion that has arisen between the next two species has 
been occasioned by applying the trivial term “ parasiticus” to 
both, and that, too, by four or five different authors in both cases, 
The word “ parasiticus” ought not to have been applied to either 
of the species, and when applied ought not to have gained any 
sanction by being used by others. The word refers to a habit that 
is common to all the species, in fact generic, and therefore im- 
properly applied to a species, because it does not define—which 
is, or ought to be, the very object of a name. 
No. 3 is the Lestris Richardsonii of Swainson; but this bird is 
also the parasiticus of Retz, Faber, Bewick, Selby, Fleming and 
Temminck. The bird figured by Bewick is three years old; your 
bird is of this species, but still older. Bewick’s black-toed gull, 
which he calls cupidatus, is a young bird in its first year: this 
bird afterwards becomes of one uniform dusky slaty brown, and 
still later acquires the buffy white colour on the sides of the neck 
and on the under surface of the body ; the two tail-feathers elongate 
with age, but the webs on each side the shaft are always lanceo- 
late, i.e. broad at the base, tapering gradually to the tips. This is 
the most common of the British species. 
No. 4. Lestris Buffonii of Boie—This species has been called 
parasiticus by Gmelin, Pallas and Gould. This bird has also 
been called the arctic; but this is objectionable, because this 
species does not go further north than No. 3, but it is much more 
rare. This bird is smaller in size than No. 3. I have never seen 
it but in its adult state, and it then has longer tail-feathers than 
