6o NATURAL SCIENCE. July, 



rare forms, no fewer than twenty-one species out of the forty-six that 

 were obtained, being previously undescribed. Special mention may 

 be made of the new species of millipede of the genus Acanthinlus, a 

 genus previously only known from a single specimen in the Paris 

 Museum, and one which in the spine-armature of its somites calls ta 

 mind some of the extinct Carboniferous members of the group. Touch- 

 ing the Myriopod fauna of Bermuda, an interesting point was revealed. 

 . This island lies within a stone's throw, so to speak, of the south- 

 eastern coast of North America, and its plants, land-shells, and insects 

 are known to be almost wholly Antillean or Nearctic in their affinities. 

 But while forty per cent, of the Myriopoda are Antillean, none are 

 certainly Nearctic, but there is, on the contrary, a strong and unmis- 

 takable infusion from the Mediterranean area of forms which occur 

 also in the Azores and Madeira. 



Of the Hexapoda, several new species of Butterflies, including 

 some interesting cases of mimicry, and of flies, beetles, etc., have 



been described. 



R. I. PococK. 



Pelagic Hemiptera. — Several beetles, flies, and other insects are 

 found on the surface of rock-pools, or under stones between tide- 

 marks. One genus of bugs (Halobates) alone among insects, is truly 

 oceanic in habit. The small extent of the field enabled Dr. F. 

 Buchanan White to transcribe all the previous hterature on the 

 subject, and to supplement the " Challenger " material by a study of 

 numerous museum specimens. He described eleven species, gave a 

 thorough account of the external structure of the insects, and re- 

 corded all known of their habits, development, and distribution. 



The species of Halobates are small, the largest known being only 

 6 mm. long (PI. xiv.. Fig. 2). They are entirely wingless, and the 

 abdomen is extremely reduced in size relatively to the thorax, the 

 second and third pairs of legs being inserted close together, near the 

 hinder end of the insect. These limbs are very long and slender, the tibial 

 and tarsal joints of the second pair being provided with a long fringe of 

 hairs. The front legs are shorter and stronger and furnished with 

 claws, by means of which the insect anchors itself to floating sub- 

 stances, which provide it with rest and food. Numbers of Halobates 

 may be observed in tropical seas, in calm weather, skimming over the 

 surface of the water ; they are to be met with near the shore, and 

 also hundreds of miles from land. 



Dr. White regarded Halobates as a very archaic type of insect, 

 believing it never to have possessed wings, and to be near the common 

 ancestor, from which it and its freshwater relations {Gerris, the Pond- 

 skater, etc.) have descended. This view is, however, controverted by 

 Dr. E. Witlaczil, who has since studied the Halobates collected by the 

 "Vettor Pisani " Expedition. He described two additional Italian 

 species {Wien. Ent. Zeit., 1886, pp. 178, 231), and, being able to make 



