A PRELIMINARY LIST OF THE INSECT*FAUNA OF MIDDLESEX. 205 
generally common among cow-parsley (Godwin); field at 
Finchley end of Bishop’s Wood, larva found (see Ent. Mo. Mag.) 
(Vaughan); near Harrow (Rowland-Brown) ; Hampstead Heath 
(Watts); Finchley (Shepherd); Old Oak Common (Mera) ; 
abundant at Willesden (Adye). 
GENERAL CONSIDERATIONS. 
Having now arrived at the end of the Macro-Lepidoptera, it 
seems opportune to consider some of the characteristics of the 
county fauna. 
When the list was first suggested, two or three very excellent 
entomologists expressed the opinion that to catalogue the fauna 
of so small an area was rather a waste of time, since the distri- 
bution of the great majority of species in England was already 
ascertained, and it was not to be expected that a Middlesex 
catalogue would add any facts of importance. From this opinion 
I was inclined altogether to dissent; and now that a fairly large 
body of facts has been presented, I believe it is possible to show 
that the insect-fauna of Middlesex is well worthy of serious 
study, and is capable of throwing light on some of the problems 
of geographical distribution. Taking the county fauna as a whole, 
it may be said to consist of six groups of species :— 
(1.) Species which belong to the fauna of the Thames Valley, 
and occur about as commonly in Middlesex as in the neighbour- 
ing counties. This includes most of the ordinary common species, 
and some that are more rare. 
(2.) Species which belong to the fauna of the Thames Valley, 
but have become rare or extinct * in Middlesex, probably, for the 
most part, within recent years. The species of Argynnis illus- 
trate this class. It can hardly be doubted that A. paphia was at 
one time common in Middlesex, and probably A. adippe. They 
still occur numerously in the neighbourhood of Maidenhead, as 
reported by Dr. H.C. Lang (Nat. Hist. Notes, 1882, p. 108). The 
present writer well remembers an enjoyable walk, in company 
with Dr. Lang, to Dropmore, to see A. adippe in the woods, 
undisturbed by anybody except the entomologist. Probably many 
species have become sensibly rarer within the past fifty years, 
especially in the immediate neighbourhood of London. Some of 
the older entomologists could, doubtless, give valuable informa- 
tion on this point. 
(3.) Species which belong to the fauna of the Thames Valley, 
but have become increasingly abundant in Middlesex of late 
years. This is another point on which information is much 
required; that there is such a class, I have little doubt. The 
decrease of woodlands and the increase of meadows, and especially 
* Stephens recorded Sphina pinastri from near Colney Hatch Wood years 
ago, but the claim of this insect to be a native nearing extinction seems 
quite doubtful. See ‘ Brit. Nat,’ Suppl., 1891, p. 49. 
