35S EAMBLES OF A NATUEALIST. [Oh. XXI. 



the calm sea, flying in gyrations near the surface, and occa- 

 sionally settling upon the water and flying, off again. I 

 watched this insect, as I presume it to have been, with much 

 interest, and was greatly, disappointed at my unsuccessful 

 attempts to secure a specimen, owing to the rapidity — 

 10-12 knots — at which we were proceeding; but I saw them 

 so often, and watched them so long, that I could not be 

 mistaken in the fact. This little yellow fly I subsequently 

 saw in the North Atlantic, between 30° and 35° N. latitude. 

 While under steam in the calms, being occupied in the 

 attempt to fish up some of the floating Acalephs and 

 Ascidians, I repeatedly observed it settle upon the water, 

 then rise and take a short erratic flight over the surface — 

 but in vain did I essay to capture a specimen. 



A notable circumstance occurred in the Indian Ocean in 

 lat. 25° S., just south of the Mauritius. For several days 

 in succession the net produced Halobatis,* glass-crabs, 

 Velellee, and the beautiful oceanic shell Janthina, of a rich, 

 deep violet colour. But what struck me as very remarkable 

 was that with the sole exception perhaps of the dark Halo- 

 batis, everything which the net contained was either trans- 

 parent and colourless, or tiuged more or less deeply with 

 the rich violet of Janthina, which indeed nearly approached 

 the sapphire-blue of the deep sea. There were small violet 



* The occurrence of this singular hemipterous insect at sea is at least very 

 remarkable. There appear to be several species, of which I met with two, 

 one on the coast of China and the other some 500 miles from land in the 

 South Indian Ocean. That they are veritable marine insects I think cannot 

 admit of a doubt, though how they exist in the open ocean is a mystery. 

 They are of a deep bluish-black, with six legs, the two hindermost furnished 

 with a delicate brush on the inner side of the tarsus. The abdomen is 

 remarkably undeveloped. Although taken occasionally in the towing net, I 

 did not find them common, and never observed any movement after capture, 

 owing to their delicate soft bodies being injured by the passage of water and 

 other things through the net. 



