1894] 



THE BRITISH NATURALIST. 



for unless the contained air is got rid of by a gradual increase in the 

 grading of the spirits of wine, before putting the larva into absolute 

 alcohol, the air-sac bursts when in Canada balsam, and scatters the 

 air bubbles throughout the micro-mount. 



You will at once recognize Fig. i in the plate, while in Fig. 2 you 

 have the dorsal view, the said air-sac being marked g. These 

 are filled with air from the tracheae, and have an exterior coating, 

 filled with pigment cells, which show up well under the ^-inch objective 

 when mounted. There are few more beautiful objects for the micro- 

 scope than the lateral plume or swimming fan (Fig. 1,/), while in the 

 dorsal view at Fig. 2, h, is seen the terminal plates full of tracheal 

 filaments. 



Passing upwards along the alimentary canal, we come to the upper 

 end of the stomach, near which is a dorsal vessel or heart, (Fig. 1, x), and 

 above this on the upper side of the muscular pharynx lie the front pair 

 of air-sacs, larger in size. On the ventral side there is a chain of nerve 

 ganglia, which runs up to a, Fig. 1 and 5, the cephalic or brain ganglia, 

 which controls the muscles of the head, of which Fig. 5 is an enlarge- 

 ment. The compound eye (Fig. 5, b) is a very beautiful object, but I 

 am rather puzzled with the saw-like organ (Fig. 5, c), above which 

 are the labial bristles (Fig. 5, d). It may be this saw is for breaking 

 up the varied entomostvaca, &c, which the long oar-like appendages (Fig. 

 5, e), or antennae, as some call them, sweep into the mouth, where they 

 are quickly seized by the prehensile organ (Fig. 5,7), with its bunches 

 of bristles, and carried to the toothed plate-like jaws or mandibles 

 (Fig. 5, k),. where they are soon reduced to a state fit for digestion. 



The Phantom Larva is also very interesting in the nymph or pupal 

 state. If you are watching his jerking leaps after food in a glass jar of 

 water, you maybe fortunate enough to witness the almost instantaneous 

 change from the larval to the pupal condition. It is most singular, for 

 instantly, with a more vigorous jerk than usual, presto ! he has 

 disappeared under your very eyes. But see, there near the top of 

 the water is floating a new and different insect altogether (Figs. 

 3 an d 4)- 



It now possesses a much larger head, and has two large projections 

 sticking up like the collar of a well-known statesman. (Lancashire 

 naturalists call it Gladstone or Randolph Churchill, according to their 

 predilections). These (Fig. 3 and 4, m) are the "trumpets" for the 

 admission of air into the tracheae, and very curious they are when 

 minutely examined. 



How very different are the tail plates of the pupa (Fig. 4, n) from 

 the posterior organs of the larva. The metamorphic changes now 

 rapidly progress, and soon the pupa bursts down the back and out 

 comes the Covethva fly or midge, balancing himself on the empty 



