NOTES ON MALACOSOMA CASTRENSIS. 151 
Notes on Malacosoma castrensis. 
By W. H. HARWOOD. 
Malacosoma castrensis seems to occur on all the extensive salt-marshes 
on the north Essex coast, between the rivers Colne and Stour. It is 
also—or was formerly—common on Mersea island. I know nothing 
personally of its distribution further south, but should think it would 
have a wide range in that direction. On this, other lepidopterists are 
likely to be better authorities than Iam. Beyond the Stour it has 
been taken in recent years on the Suffolk side at Felixstowe, and many 
years ago the late Mr. N. I’. Hele bred a few specimens from larve 
obtained near Aldborough. These were probably the offspring of some 
strageling female, which had in some way got far beyond its normal 
limits, but it may occur naturally further north, as in all probability 
neither the Suffolk nor Norfolk coasts have ever been properly searched 
for it by anyone acquainted with its habits. Meyrick, I see, gives 
York as a locality, and it would be interesting to have particulars on 
this point, as one would not expect to find it so far from the Thames, 
to the banks of which it was formerly thought to be exclusively confined. 
The larve are polyphagous, and it is rather difficult to say what saline 
plants they will not eat. Among others, I may mention that they are 
partial to Artemisia maritima, Armeria maritima, Statice limontun, 
Plantago maritima, Silene maritima, Inula crithmoides and Atriplex 
portulacoides, but, perhaps, Artemisia, Statice and Plantayo are the 
favourites. 
It is a very uncertain species, for though it seems to occur regularly 
it is sometimes very far from common, and at other times very 
abundant. The full-fed larve generally conceal themselves very 
effectually during the heat of the day, and come out to feed in the 
evening, when numbers may be found crawling or feeding where they 
might have been searched for in vain a few hours previously, but 
sometimes they may be found in the earlier part of the day, and, of 
course, the young broods may be found at rest on their webs at all 
times. 
They are especially common some seasons along the base of the sea- 
wall, and this is to be easily accounted for, as the eges are ‘‘ lacquered ”’ 
round the stems of grass and other plants, and when these become 
sere and brittle they are frequently broken off and borne by the 
incoming tides towards the sea-wall, where, sometimes, they can be 
easily detected by a quick eye, I frequently find them in this way, 
but generally leave them, unless the situation seems to be very 
unfavourable. Some years ago a number of gentlemen, actuated by 
the best intentions, published a very remarkable list of British lepidop- 
tera, that stood in need of protection from the rapacity of collectors, 
in which they included a number of species that are perfectly safe, and 
out of which they left others that had far stronger claim to be included. 
Among the former was J/. castrensis. The most rapacious collector 
can, ina favourable season, obtain quite as many larve as he can 
desire, and yet produce no appreciable effect, considering the very 
small area over which he can search for them, and the great number 
to be found within a very limited space; but it is a great mistake to 
take too many, for they require an immense deal of room to roam about 
in, and if many are confined within narrow linits, instead of the large 
