NOTES ON 5IALACOS05IA CASTRENSIS. 151 



Notes on Malacosoma castrensis. 



By W, H. HAEWOOD. 



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 Avas formerly — common on Mersea island. I knoAV 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 I am. Beyond the Stour it has 

 been taken in recent years on the Suffolk side at Felixstowe, and many 

 years ago the late Mr. N. F. Hele bred a few specimens from larv^ 

 obtained near Aldborough. These were probably the offspring of some 

 straggling female, which had in some Avay 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 Avhich it Avas formerly thought to be exclusively confined. 

 The larvffi are polyphagous, and it is rather difiicult to say Avhat saline 

 plants they will not eat. Among others, I may mention that they are 

 partial to Artemisia maritima, Aniieria maritima, Statice livKinium, 

 Plantago maritima, Silene maritima, Inula critJtmoides and Atriplex 

 portnlacoides, but, perhaps, Artemisia, Statice and Planta<jo 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 larvfe generally conceal themselves very 

 effectually during the heat of the day, and come out to feed in the 

 evening, Avhen numbers may be found crawling or feeding Avhere 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 eggs 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-Avall, Avhere, 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 Avhich they left others that had far stronger claim to be included. 

 Among the former was 3/. castrensis. The most rapacious collector 

 can, in a favourable season, obtain quite as many larvae 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 limits, instead of the large 



