196 



KNOWLEDGE. 



[Septfmukr, 1901. 



thrown up by the tide. Two most remarkable members 

 of this group have been found by the Rev. A. E. Eaton 

 on the shores of the far southern island of Kerguelen.J 

 One — Anomalopteryx maritima, Eaton, with narrow 

 strap-like wings, haunts the nests of sea-birds ; while 

 the other, Apetenus liioralU, Eaton, creeps over the 

 stones of the beach. 



Several small flies of prey belonging to the family 

 Empidae may be found on our coasts, often occun'ing 

 in great companies. Though this family is structurally 

 far removed from the groups mentioned above, the 

 sensitive bristle of the feeler, for rxamjjle, being borne 

 at the tip, not on the edge of the tenninal segment, and 

 the grub possessing a distinct head — Haliday pointed 

 out the likeness to Coelopa in the general aspect of these 

 marine Empids. The most characteristic of them belong 

 to the genus Chersodromia. Perhaps the most note^ 

 worthy species is C. arenaria, Halid. (Fig. 4), in which 

 the wings are so shortened as to be useless for flight — 

 a character, as we have seen, rather frequent among the 

 insects of the sea-shore. Apparently this genus occurs 

 only on our islands and the Scandinavian coasts. 



Another family represented on the sea-shore whose 

 members live by prey is the Dolichopodidie. These 

 are slender, agile flies, often of bright blue or green 

 metallic colouis ; they are very numerous in species, 

 and often haunt the margins of lakes and streams, 

 running over the surface of the water in pursuit of 

 their prey. Some of the more daring members of this 

 family live close to the edge of the sea within reach of 

 the spray of the breakers, and find their victims in the 

 weaker insects of the shore. Several of the large genera 

 such as Dolichopus and Hydrophorus have each a few 

 maritime representatives, while Machaerium, with only 

 one species — M. maritimce, Halid. — seems to be confined 

 to seaside marshes, and Thinophilus and Aphrosylus 

 (Fig. 5) each with two or three species are only to be 



Fio. 



(After 



Fio. 5. Fio. 



Aphrosylus raptor. ma\v. M.agiiificd 3 time.'*. 

 Westwood.) 

 Fig. 6.— (inih of Apjirosylus. Maguificd 12 timrs. (.Af oi- Wlipder.) 



found close to the edge of the wat«r, occurring on rocks 

 and seaweed washed by the waves. The species of 

 Thinophilus arc bronzy in aspect, but the Aphrosyli 

 have the ashy grey hue characteristic of so many sear 

 shore insects. The specific names raptor and ferox, 



t G. II. Verrall. "Zoology, of Kerguelen Island, Diptera." 

 Thil. Trans. S. Soe., Extra Vol.CLWIII . 1879. ])p. 228-48. 



bestowed on them by their describer, A. H. Haliday, 

 sufficiently indicate their habits. For many years 

 Aphrosylus was known only on the British, Irish, and 

 Italian shores, but quite recently three species have 

 been discovered on the Pacific coast of North America 

 by Prof. Wheeler, § who was fortunate enough to find 

 the curious gnib of one of them (Fig. 6) among the 

 seaweed covering the rocks. 



But the most perfectly adapted to marine life of all 

 the flies of the sea-shore are minute in size, and belnng 

 to one of the lowliest families of the order-the Midges 

 or Chironomidw. Though small, these arc among the 

 most familiar of insects; they may often be seen on a 

 summer evening flying in swarms over the waters of 

 ponds and streams in which their grubs live. The best 

 known species of the family, Vhirunnwiix plumriK>i>!. and 

 its burrowing red gi-ub the " blood-worm," together with 

 some allied forms have been lately described in detail 

 by Miall and Hammond. || The Chironomidse are 

 readily to be distinguished from the gnats or 

 mosquitoes (Culicidae) by the great reduction of the 

 jaws, which renders them incapable of biting and by 

 the simplicity of the wing-neuiation. 



One or two species of Chironomus haunt the rocks 

 exposed at low-tide, and their grubs live in the sea 

 as happily as the gi-ubs of their relations live in fresh 

 water. Prof. Miall has found that the fresh water 

 lai-\'£e cannot long sui-vive transference to salt water. 

 Possibly by gradually increasing the degree of 

 salinity, acciimatisation might be brought about in the 

 lifetime of an individual, but there can be no doubt 

 that in the course of generations these marine midge- 

 grubs have become well-used to their strange suiTound- 

 ings. One of them which has been dredged off our 

 coasts from a depth of 15 fathoms was described in 

 the first instance as a marine annelid under the name 

 of C'ompnnfifi rruriformh. Except in its colour, which 

 is appropriately a light sea-green, this creatiU'e closely 

 resembles an ordinary 'blood-worm," possessing a pair 

 of sucker-feet at either end of its body, and tubular 

 '■ blood-gills " on the two hindmost segments. Mr. 

 Swainson has lately found this grub on hydroids at 

 various parts of the British coast. "i It may perhaps 

 prove to belong not to a Chironomus in the strict sense, 

 but to the closely allied genus Thalassomyia (which 

 possesses but one species, T. Frauenfeldii, Schiner) dis- 

 tinguished by the short, broad, and emarg^nate fourth 

 tarsal segment. On the shores of the Adriatic, this 

 midge was found sitting on rocks within reach of the 

 spray, and it has been noticed on the coast of the Isle 

 of Wight ill a somewhat similar situation resting on 

 the walls of a cave, where the spray constantlv washed 

 over it. 



Marine midges have been found on the other side of 

 the Atlantic. A grub dredged from the depth of 20 

 fathoms off the coast of Massachusetts and its parent 

 fly were described by Prof. Packard*" in 1S69 under 

 the name of Cliirnnomiis oceaninis. As might be 

 expected they have not escaped the notice of French 

 naturalist^s. In 1892, Prof. Moniez described a marine 

 Chiionomus from the shores of the Channel remarkable 



§ W. M. Whoi'ler. " A Genus of Maritime I)olic1io]iO(U(lie now to 

 America." Proc. Cat. Aead. Sd. (3) Vol. I ; 1897, ]i|>. U5-152. jil. 4. 



11 L. C. Miall & A. R. Hnmiiiontl. "The Struct urr and Life- 

 History of the Harlequin Fly (Chironomus)." OxforJ, 1900. 



IT See F. V. Theobald. " .\n Account of British Flies," Vol. I. 

 ([ip. 202-;!). Loudon, 1892. 



** A. S. Packard. "On Insects inbabitiug Salt Water." Froc. 

 E.'.-.iex Inst. (Salem, Maes.), Vol. VI., 18fi9, pp. 41-51. 



