329 IMPERFECT SOCIETIES OF INSECTS. 



I wish you may have the good fortune next year to be a spectator of 

 this all but celestial dance. In the meantime, in May and June, their 

 season of love, you may often receive much gratification from observing 

 the motions of a countless host of little black flies of the genus Hilara 

 (H. maurd), which at this period of the year assemble to wheel in aery 

 circles over stagnant waters, with a rush resembling that of a hasty shower 

 driven by the wind. 



Here, also, must be noticed the bombadier beetles {Brachinus crepi- 

 tans), which, with several others of the same family, are usually found 

 together in considerable numbers under stones, &,c., and the red field-bugs 

 Cimex {Pyrrhocoris) apieriis, which, in like manner, have a very social 

 propensity, though in both instances we are ignorant of any common 

 labors or other motive than the love of society, which can lead them to 

 associate. The same may be also said as to the numerous assemblages of 

 a moth (^Scotophila Trngopogims) , mentioned by JM. de V^illiers, which 

 he finds in July under the bark of willows, ranged side by side, generally 

 touching each other, and with the head always turned the same way, and 

 which if you disturb them do not attempt to fly, but run upon the backs 

 of their companions, which exhibit no marks of alarm. ^ 



The next description of insect associations is of those that congregate 

 for the purpose of traveling or emigrating together. De Geer has given 

 an account of the larvae of certain gnats {Tipidarice) which assemble in 

 considerable numbers for this purpose, so as to form a band of a finger's 

 breadth, and of from one to two yards in length. And, what is remark- 

 able, while upon their march, which is very slow, they adhere to each 

 other by a kind of glutinous secretion ; but when disturbed they separate 

 without difficulty.^ Kuhn mentions another of the same tribe — from the 

 antennae in his figure, which is very indifferent, it should seem a species 

 of agaric-gnat (JSlycetophila) , — the larva? of which live in society, and 

 emigrate in files, like the caterpillar of the procession-moth. First goes 

 one, next follow two, then three, &;c., so as to exhibit a serpentine 

 appearance, probably from their simultaneous undulating motion, and the 

 continuity of the files, whence the common people in Germany call them 

 (or rather the file when on march) heerwurm, and view them with great 

 dread, regarding them as ominous of war. These larvae are apodes, white, 

 sub-transparent, with black heads.^ The caterpillars of a moth Is'octua 

 (Xylojjhasia ?) Ewingii Westw., a native of Van Diemen's Land, exhib- 

 ited a singular migrating propensity as described by Thomas I. Ewing, 

 Esq., who has given them the name of the " migrating caterpillars.'* 

 Passing, about December 20th, from a barley field which had been 

 ploughed up, and which seemed literally in motion with them, they pro- 

 ceeded up the road, entered at the gateway into the lawn, then crossed 

 the verandah in front of the house, and through two gardens until they 

 reached a field laid down with English grasses, on which they committed 

 sad havoc. Many of them did not stop there, as the whole road from 

 the field to the town was black with them. They did not cease migrating 

 for a fortnight, proceeding with a quick and almost running motion over 

 <}very obstacle, whether walls or shrubs, &,c., and making a sudden halt 



• Ann. Soc. Ent. de France, xi. bull. xi». 



« De Geer, vi. 338. ^ Naturforsch. xvii. 226. 



