130 
PSYCHE 
[October 
remarks on tlie swarming of Cule.v cantons, observed twice tjy Theobald in the fens, 
shows a distinct mode of swarming in this species. Tliese swarms, composed of 
both sexes, formed dense clouds which quite darkened the air. “These insect-clouds 
Avere constantly moving up and down about ten to twelve feet above the ground. 
At times the noise they produced could be heard a (juarter of a mile off, then it woidd 
suddenly cease for some time and commence again.” It is to be supposed that Mr. 
Theobald is not to be taken literally when he says the insect clouds were constantly 
moving up and down but that the motion applies to the individuals in the swarms, as 
in the foregoing observations. 
Radi has written two most interesting and suggestive papers on the light-reac- 
tions of Arthrojiods and a great part of his discussion is based on the behavior of 
swarming insects, particularly of Culicids and Chironomids. It Avould lead too far 
to enter into a discussion of these papers, but the fact is lirought out that these insects 
orient themselves towards some definite object which is differentiated from its sur- 
roundings either by greater prominence or a difference in color. He not only cites 
instances of orientation toAvards trees, bushes, sign-posts, or even heads of grass, but 
others Avhere the SAvarms hoA-ered o\’er paths through fields, or spots of ditferent color 
but not elevated aboA'e the surroundings. The swarms oA’er spots on the ground in 
all probability belong to different species from those attracted to prominent objects. 
Radi confesses that he made no attempt at close determination of the in.sects under 
observation and it is evident that he had no conception of the number of forms of 
similar but distinct habits that he might have before him. In consequence his 
statements are far too general and much that might haA'e been used for or against his 
contention has escaped him. 
Little as Ave yet knoAv of the subject, it Avill be Avell to state right here that, even 
Avithin the Culicidae, there is not only a marked diA’ersity in the mode of SAA’arming 
of ditferent species, but that there are many forms which do not swarm at all. In 
the case of the almost exclusi\'ely house-inhabiting Stegomyia calopus, as Goeldi has 
shoAvn, there are no such sAA'arms as in Cule.v proper. The males congregate in little 
groups of 15 or 20, hovering over the corner of a cabinet or other prominent object, 
and pounce upon the females that come Avithin range. I can add that copulation 
frequently takes place Avhen there is no evidence of even such Aveak sAvarms. It 
should be noted that in Stegomyia co])ulation takes place during the brightest j)art 
of the day. On the other hand I have u])on two occasions observeil small sAAarms 
of Stegomyia (presumal)ly males) hovering over the heads of persons, in both cases 
shortly before sunset. Once this occurred ujion the hotel-verantla at Cordoba, 
[Mexico, and again in the street at Acapulco, OAer the heads of passers and keeping 
along with them. In this case the meaning of the SAvarms would be hard to inter- 
