POSITION OF SWARMS 125 
there are a number of trees, and from the top of nearly every tree three or four 
of the strange, smokelike columns could be seen standing up in the air, always 
straight but not always vertical, some of them being inclined at small angles. 
. . . On watching one of the columns closely, it was apparent that all the gnats 
had their heads one way, facing the breeze, which, however, was a very light one. 
It was a calm evening; what air-current there was came from the south-east. 
It seemed to be sufficient occasionally to press back the column a few inches 
from its normal position, and whenever this happened the whole body of gnats 
jerked themselves forward again with one perfectly synchronous impulse.’ 
“ A picturesque account of a remarkable swarming of Culices, at Lewisham 
Road near London, is given by Douglas. During ten days he observed ‘ the air 
thick with millions of them, at times charging in close column up the road, like 
a squadron of cavalry, at other times engaged in dancing up and down, after the 
manner of their race.’ These swarms were in evidence only during the hour 
before dark and it appears were over or near the road, within reach of the 
riding whips and sticks of the ‘ profanum vulgus.’ Near by ‘ are several tall 
trees, and round the top of the highest one only, at the same hour of the evening 
that the periodical saltatory performances are going on in the road, enormous 
swarms of gnats congregate. At first they appear as a small black cloud curling 
about the ends of the branches, and soon, when the air is calm, rising in a close 
column, like smoke from a chimney, for a distance of some 20 or 30 feet, the 
bulk gradually becoming more grey and attenuated until lost to sight in the 
upward progress. When a breeze is moving, the insects, always preserving close 
order, are blown out laterally, and after skirmishing with the wind return to 
their cover among the top leaves of the tree.” This last remark may be an as- 
sumption and at such distance from the ground could hardly have been based 
upon actual observation. Douglas suspects that the species in the tree was ‘ not 
the same as that of the acrobats of the road, and with right; unfortunately 
neither form was definitely identified. It further appears from the remarks of 
Douglas that these swarms are an annual occurrence, only that the number of 
individuals varies greatly from year to year. 
“Tn all the foregoing notes the writers failed to notice the true function of 
these gatherings of Nemocera. However it had not escaped that keen observer 
Gilbert White. He was evidently uncertain of the identity of the insects con- 
cerned, for in his posthumously published notes he calls them ‘empedes or 
tipule.’ Speaking of their swarms at evening he says: ‘ At this juncture they 
sport and copulate; as it grows more dark they retire. All day they hide in the 
hedges. As they rise in a cloud they appear like smoke.’ No further mention 
of copulation in connection with swarming appears until Taschenberg’s popular 
account of Culex pipiens, published in 1882. He notes their habit of gathering 
at the gables of houses and other prominences and describes how the females fly 
to the swarm of males to effect copulation. In the notes on the swarming of 
Chironomide which follow, Taschenberg describes the formation over trees and 
in tall columns, and we are left to infer that the Culex swarms do not assume the 
columnar form—at least not in the same degree. 
* * % * * % * * 
“ Radl has written two most interesting and suggestive papers on the light- 
reactions of Arthropods and a great part of his discussion is based on the be- 
havior of swarming insects, particularly of Culicids and Chironomids. It 
would lead too far to enter into a discussion of these papers, but the fact is 
brought out that these insects orient themselves towards some definite object 
which is differentiated from its surroundings either by greater prominence or a 
difference in color. He not only cites instances of orientation towards trees, 
