1919.] ]5 



specimens have not been kept, but it seems almost certain that the same 

 species is meant : — 



HaywanVs Heath, Sussex. — In a letter written on Aug. let, 1918, it is 

 stated that they were in thousands in a house, in rooms facing north and south, 

 but not in those having other aspects. They get behind pictures and make 

 the walls look black in patches. They appear in August or the end of July, 

 and seem to have infested the house for several seasons in succession. The 

 house is on a hill-top, and surrounded by a wood of ash and oak. 



£ast Grinstead, Sussex. — A record of a swarm was received on Oct. 31st, 

 1918. 



Mr. Fryer has had other inquiries about the matter, but details have 

 not been recorded. With the exception of Felden, Herts, all the above 

 records are from Surrey, Sussex, and Kent, in which part of the country 

 there seems to have been a remarkable concurrence of swarms. 



There is no satisfactory explanation of these swarms at present, 

 though the habit was known to Walker as long ago as 1835. Possibly 

 the insects merely enter buildings for shelter, as seems to be the case 

 with the immense swarms of Chloropid and other flies, about which much 

 has been written. If so, their appearance as early as July is noteworthy, 

 but would depend, presumably, on the season of emergence from their 

 hosts and of their egg-laying*. Keasons for doubting whether the}'' 

 originate in the buildings where they occur, from Anobiid beetles in the 

 woodwork, have been mentioned. They have been observed definitely to 

 enter from withoiit ; moreover, would not incredible numbers of Anobiids 

 have to be present for such myriads of parasites to be bred from them, 

 even if many emerged from a single host? If Walker's other suppo- 

 sition — that one of their hosts is Tortrix viridana — be true, then the 

 extreme abundance of the parasite during the last year or two is partly 

 comprehensible, since T. viridana has been only too numerous, and has 

 had a share in the serious defoliation of our oak woods. 



Clearer information is needed as to the hosts of the Pteromahis. 

 The older records are sometimes wanting in definite proof of the parasite 

 being bred from a particular host, and it is doubtful whether the deter- 

 minations of the species of Pteromalus are always correct. What has 

 been written may be briefly summarised : 



Audouin (1842, Hist. Ins. nuisibles a la vigne, p. 187) includes F. depUmatus 

 among the enemies of the Vine Pyrale, Spart/anothis pilleriana, but apparently 



* Lesne (Bull. Soc. ent. France, 1909, p. 273), under the designation " sommeil hibernal 

 precoce," records that as early as mid-July, 1904, numbers of a species of Vaties^a were collected in 

 groups in houses in a village of the High Jura; this was at an elevation of over 1100 metres, but 

 July and August of that year in the High Jura were very hot, and the weather almost continually 

 fine. He alludes also to numerous observations which have been made on the earlj' appearance of 

 GalerucelUi Ixdeola Midi, in human habitations, the suggested explanation in this case being that 

 excessive multiplication of the insect has led to exhaustion of its food-supply. 



