122 THE ENTOMOLOGIST. 



functions of this intricate cord-like structure ? What part does 

 it play in the economy of the insect's life? Balbiani (1881) has 

 given us much information resjDecting the salivary cells and 

 nuclei of the Chironomiis larva, to whose exhaustive remarks 

 Miall (1895) has added some important observations ; but so far 

 no entomological biologist has been able to throw any light upon 

 the very peculiar cords to which I have ventured to direct your 

 attention. 



There is another gnat-like fly (Corethra plumicornis) which 

 deposits her eggs in a flat mass on the surface of still and shaded 

 pools. From these emerge long slender transi^arent creatures 

 that, from their peculiar habit of suddenly disappearing by 

 rapidly changing their position, have not inaptly been designated 

 *' phantom larvse." They are highly predaceous, and somewhat 

 smaller than the bloodworms. Limbs are absent, unless a 

 hooked foot-like protuberance at the tail-end can be described as 

 such ; but the antennae being prehensile, the larva makes good 

 use of these in the capture of its prey, which consists for the 

 most part of small aquatic organisms of various kinds. But the 

 curious part about the phantom larvae is that, although requiring 

 air for breathing purposes, it possesses no spiracles. Is respira- 

 tion carried on through the body-wall ? For, notwithstanding 

 the apparent total absence of external orifices, there is neverthe- 

 less a partially developed tracheal system consisting of two tubes 

 running longitudinally through the insect, which, although devoid 

 of air throughout their greater length, dilate into large well-filled 

 air-sacs towards either extremity of the body. Prof. Miall has 

 discovered that in newly-hatched larvae neither the tubes nor 

 sacs contain any air whatever, and, although a good deal of 

 attention has been devoted to the subject, we are not yet in 

 possession of any facts to lead us to the knowledge as to how air 

 is first admitted to the air-chambers, or subsequently renewed. 

 Is gas generated by the larva itself in a similar way to that by 

 which some fishes are known to inflate their swimming-bladders, 

 and some zoophytes their floats ? Bohr and Moreau have given 

 much attention to this latter subject, and the former has shown 

 us that the air-bladder of a fish completely refills after puncture, 

 the gas generated containing as much as 80 per cent, of oxygen. 

 Does the minute larva of Corethra employ similar methods to 

 the nautilus, or how is its air evolved ? This is yet another of 

 Nature's unsolved mysteries, the satisfactory unravelment of 

 which would probably help us very considerably to understand 

 the fact of the possession of highly oxydised air by many other 

 aquatic animals. 



Such, then, are a few of the legion of pertinent questions 

 which ever confront the biological investigator — problems that 

 the entomological student will constantly meet with on every 

 hand. I might allude to many puzzling circumstances in the 



