60 [March, 



Crawley, Sussex. Earlj^ in 1020 I liefird that infestations of liouses liad 

 occurred in tliis district, but did not see specimens of tlie insects or go into the 

 matter in detail. 



IIand'i?corth, Birmingham. A small visitation is recorded by Mr. 0. J. 

 Waiuwright, Ent. Mo. Mag. 1922, p. 39. 



Felden, Herts. In my earlier paper (p. 14) I mentioned that a swarm 

 liad occurred in this place, but gave no details. Mr. Claude Morley has now 

 kindly told me that the insects wei*e present only on the South-East window 

 of a bedroom with three windows, in the late Albert Piffard's house, and that 

 tlie date when he saw them was September 27th-October 1st, 1901. The date 

 of the year is worthj^ of note, because it is possible that there is a definite 

 periodicity in the occurrence of these swarms of parasites, depending on n 

 periodicity in the extra abundance of their hosts, as has been observed with 

 other parasites and their hosts. It may be that swarms occurred about 1901, 

 and that then followed a cycle of years in which the Chalcidids were not so 

 numerous as to swarm, till they began to attract notice again by their myiiads 

 from about 1916 onwards. 



B. Stekomalus muscaeum. This Chalcidid also is known to 

 swarm in liouses at times, and two occurrences of this which have come 

 to my notice may be recorded. It seems that nothing is known with 

 real certainty as to the hosts of tliis parasite, though it is said to have 

 been bred from puparia of Muscid flies. 



Little Shelford, Cambridgeshire. A great swarm occurred in 1920 at the 

 house of the late J. F. Eaden, M.A. A sample from the infested rooms, 

 received 22. xi. 1920, consisted almost entirely of the Anthomyiid fly Zm/wo- 

 fhora humilis Zett. { = s€pte7nnotata Zett.), of wdiich about 100 examples, all 5> 

 were counted *, and of Stenomalus muscanim (J. Waterston det.), of which 

 several thousands at least, all 5? were present. Besides these two species the 

 sample contained only six specimens of Pteromalus deplanatus: also a single 

 specimen of lihgpMis and of a Culicid, but these might occur on any window, 

 and cannot be regarded as part of the swarm. 



Mrs. Eaden stated that visitations of myriads of small insects have taken 

 place in the house for a long succession of years. A number of rooms are 

 affected more or less, but especially three first-floor rooms facing South-East 

 and one (warmed by pipes) facing North-West. The South-East rooms are 

 three in a row, two large rooms each with a big window, and between them a 

 smaller room with a much smaller window : the two big rooms are heavily, 

 but the small room verj-^ little, infested. The iiisects are most numerous in 

 the narrow crevices round the window-sashes. They have not been observed 

 to get behind the glass of pictures. The flies appeared about the end of 

 August, the Chalcidids later, about September. The insects disappear in 

 frosty w^ealher. It is thouoht that the Chalcidids have been preeent in the 



* The house at Little Shelford is distant about P>k miles as the crow flies from Babraham Hall, 

 where occurred the vast swariii of Limn ophor a and of Chhropisca recrded by tlie writer, Ent. Mo. 

 Mag. 1918, p. 18. Since then a number of records have been published on swarms, especially in 

 Scotland, of which the Limnopkora was a principal component: see " Scottish Naturalist," 1916 

 pp. 81, 114, 139; 1917, p. 118 : c/. Ent. Mo. Mag. 19^2, pp. 20, 38. 



