1919.1 13 



SWAEMING OF THE CHALCIDID PTER0MALU8 DEPLANATUS Nees 



IN BUILDINGS. 



BT HUGH SCOTT, M.A., F.L.S., F.E.S. 



''^ A paragraph on the swarming in rooms of myriads of Pferomalus 

 (leplanafiis Nees { = domesticus Walker), appeared in " Natui-e," 

 Sept. 19th, 1918 (vol. cii, p. 50). This note was based on informa- 

 tion supplied bv Mr. K. Gr. Blair, to whom had been submitted samples 

 and i^artieulars of swarms in various places. 



The main purpose of the present article is to give details of a vast 

 swarm of this species which has occurred for three years in succession 

 (1916-18) at Hascombe, near Godalming, Surrey. Specimens sent to 

 me late in 1917 were determined by Mr. Waterston, and recently the 

 rector of Hascombe, the Rev. C. Sadler, has kindly sent me a much 

 larger sample, taken from the 1918 swarm, with full information. 



The buildings affected include all parts of Hascombe Church, 

 especially the vestry, also the rectory and at least two other houses, one 

 of which is a mile or more away. The invasion is not restricted to parts 

 of buildings with a particular aspect, for rooms facing south, south- 

 east, east, and north-west are all affected. But the insects do appear 

 sometimes to keep to particular rooms in a house : thus, in the rectorj 

 they swarmed in the first year in rooms facing east, but in 1918 thej 

 also appeared, though in smaller numbers, in two rooms with a south 

 aspect ; while, on the other hand, in the house a mile away nearly every 

 room is invaded. 



The invasion begins about the middle of July and lasts, if the 

 weather is seasonable, till about the end of August. This tallies with 

 Walker's statement, written in 1835 (Ent. Mag. ii, p. 481), that the 

 insect " occurs on the windows and walls of houses in infinite numbers 

 during July, and more sparingly during the rest of the year." Mr. Sadler 

 asserts definitely that, at any rate as far as his house is concerned, they 

 invade tlie rooms from outside, usually on hot sultry days between 

 about 11.30 and 4 p.m., and he has often closed the windows at such 

 times in an attempt to stop the incoming hordes. This is interesting 

 in connection with the seemingly unproved supposition that the parasites 

 originate in the buildings from Anobiid beetles in the woodwork: if so, 

 why should they enter these rooms from without ? unless, indeed, they 

 were bred from Anobiids in the woodwork of the church, and invaded 

 the house from there. My informant also noticed that although they 

 fly actively while outside, when inside the rooms they only crawl. Some 

 hundi'eds sent to me during the first week in November emerged when 



