2 IS 



KNOWLEDGE. 



[November, 1901. 



coutiibuted to the " Challenger " Reports. ft Since bis 

 work some studies on the internal anatomy of the inserts 

 have been made by Witlaczil and Nassouoff, while our 

 naval entomologist Mr. J. J. Walker has contributed 

 some valuable observations on their habits and life 

 history. 



The most striking featm-es of internal structure are 

 the presence in the thorax of organs usually found in 

 the abdomen (on account of the great reduction of the 

 latter region) and the immense development of the 

 muscles for working the long middle and hind legs. 

 A remarkable gland ("belly-gland" of Nassonoff) opens 

 beneath the foremost abdominal segment in both sexes. 

 The tail end of the body is highly modified in the 

 male (Figs. 7-S). 



Fifteen sjDecies are known, most of which are restricted 

 to one or other of the great oceans, but Halohnte^ 

 s'riceus. Eschs. occurs both in the Atlantic and Pacific, 

 while H. micang, Eschs. {:=WuUerstorfi. Frauenf.) i-anges 

 over the whole oceanic area of the tropics. Apparently 

 these insects cannot exist without a considerable amount 

 of heat, as they are almost unknown on the temperate 

 ssas; stray examples of II. inicam^ have occm-red as far- 

 north as Spain and Carolina. They abound most near 

 the shores, and have even been observed jumping about 

 ssaweed cast up on the Red Sea beach. But tliey have 

 been noticed more than 1000 miles from anv land. Their 

 brick-red eggs are veiy large as compared with the size 

 of the mother, who sometimes carries two or three about 

 attached to the under sm-facc of her body. AVitlaczil 

 records that the Italian survej'ing ship '' Vettor Pisani " 

 picked up in the Pacific Ocean, oft' Galapagos Island, a 

 floating bird's feather covered with masses of eggs of 

 Halobates, siu-rounded with a gelatinous envelope. It 

 seems therefore that the eggs are laid on floating objects. 



Floating objects, indeed, serve these tiny ocean- 

 travellers \\-ith much-needed rest and food. They have 

 be€n noticed clinging by their anchor-like fore-claws to 

 masses of seaweed and they suck the juices of jelly-fish. 

 Their fresh-water relations, the pond-skaters, are often 

 described as predaceous, but they seem to prefer a dead 

 or dying to a, living victim. Probably, therefore Halo- 

 bates arc to be reckoned among the scavengers of the 

 sea. Of their manner of life, Mr. Walker writes : — " In 

 tropical latitudes, when a sailing ship is becalmed or 

 a steamer is stopped in a perfectly calm sea, it is not 

 long before little whitish creatures are seen rapidly 

 skimming over the glassy siu-face with a sinuous motion, 

 and soon half a dozen or more Halobates are in view 

 a-: once, evidently attracted by the bulky hull of the 

 ship, which they will approach frequentlv within arm's 

 length. Their progi-ess appears to be effected bv a sort 

 of skating action of the long ciliated legs. ." . 

 A heavy swell, provided the weather is quite calm, does 

 not prevent their appearance, but with the ripple caused 

 by the slightest breeze thev vanish at once; though 

 sometimes they were to be found in plenty on the 

 narrow belt of smooth water to leewai-d of the ship, 

 when not one was to be seen on the windward side.'" 

 I\lr. Walker kept specimens alive, confined in a vessel 

 of sea-water. " On the approach of the finger or a pencil 



they dive readily, and swim with great facility beneath 

 the surface, the air entangled in the pubescence giving 

 them a beautiful appearance like that of a globule of 

 mercury or polished silver. This supply of air must 

 be essential to the existence of the insects, which I feel 

 sure must pass a lai-ge part of their life beneath the 

 surface of the sea, diving into undisturbed water in 

 rough or even in moderate weather, and coming up 

 again only when it is absolutely calm.'' 



Considerable difference of opinion has prevailed 

 among the students of these insects as to their exact 

 relationship to their fresh-water allies. Buchanan 

 White considered them a vei-y archaic group, doubted 

 if they ever possessed wings, and. laying stress on their 

 likeness to the young nymphs of the pond-skaters, was 

 inclined to regard them as ancestral to the Gerridse. 

 ^^'itlaczil and Xassonoff on the other hand consider 

 them highly modified and aberrant forms. There can 

 be little doubt that this latter opinion is nearer the 

 truth, as the loss of wings in maiine insects can be 

 traced under our veiy eyes, notably in the related genus 

 Metrocoris, and the likeness of the pond-skater nymph 

 is much more marked to the yoiing (Fig. 9) than to the 

 adult Halobates. Still, the pelagic life of Halobates 

 shows that a long period must have elapsed since 

 their immediate ancestors forsook the fresh-water for 

 " that great and wide sea wherein ai'e things creeping 

 iiiniunerable, both small and gi-eat beasts." Among all 

 the living creatures of the sea few yield in interest and 

 mysteiy to these frail insects. 



It is likely that the animal life of our globe began in 

 the waters of the sea. But the largest monsters of the 

 deep, the great whales and their kindred, together with 

 these " Insects of the Sea,'' ai'e undoubtedly invaders 

 from the land — driven out of the crowded continents to 

 find a home, if not a resting-place, in that vast ocean 

 which was the cradle of their far-off ancestors in the 

 early ages of the eai-th's historv. 



++ F. Biiclianaii 'Wluto. " Kepoi-t ou the Pelagic Upmiptera " 

 "Challenger ' Zoolo;iii. Vol. VII.— J. J. Walker. "On the genus 

 Halobates and otlier JIarine Hcmiptera." i:nt Mo Man f-'l 

 V„l. IV.. 1893, pp. 227-232.-E. Witlaezil. " Z«r Kenntnis cle^ 

 Gattung Halobates." Zool. Anz, Vol. X., 1887, pp. 336-9.— N. 

 Xassonoff. "Halobates flarirentris var Kudrini " (in Kiissian) 

 Warsaw, 1,894 (abst. in Zool. Centrahl. Vol. I., pp. 702-4 \ For 

 further modern liK^raturc ,=ee G. H. Carpenter. "Challenger Expedi- 

 tion." 3'a/. .S>(.. Vol. VII., 1895, ))p. 60-61. 



CONSTELLATION STUDIES. 



By E. Walter Maunder, f.e.a.s. 



X.— THE ROYAL FAMILY. 



Above the long group of watery constellatioub, with 

 which we have been occupied of late, and connected 

 with them, may be seen a cluster of constellation figures 

 which, unicjue amongst the stellar designs, set forth a 

 distinct and well-recognized stoi-y. These are the five 

 constellations which, together with Cetus, presei-ve to 

 us the legend of Perseus and the maiden whom he 

 delivered. The story, as it has come down to us from 

 Greek sources, is one beloved of romancists in all ages 

 and in all lands. A lovely maiden, innocent herself of 

 any fault, is yet condemned, in order to expiate the 

 offences of her parents, to be exposed to some terrible 

 disaster. Her case seems beyond hope or help when at 

 the very crisis of her fate, a young hero who has already 

 abundantly proved his mettle in other fields, appears 

 on the scene. Her beauty and her distress alike appeal 

 to him ; and to his victorious powers, her deliverance 

 is a light task. The threatening monster is easily dis- 

 posed of, and what promised to be a grim and terrible 

 tragedy, ends with triumph and rejoicing to the sound 

 of wedding bells. 



It may be, as Brown assures us. that we have in the 

 Andromeda legend but another version of the all-per- 

 vading solar myth. Perseus may be Bai--Sav, the son 

 of hair, that is to sav, the solar Heraklcs clad in his 



