AuousT 1, 1898.] 



KNOWLEDGE. 



179 



holdfasts, and are driven through the upper cuticle, and 

 the pupal stage is reached (Fig. 8), though sometimes 

 the larva quits the leaf and falls to the ground to undergo 

 this change. The fly is soon matured, and, bursting 

 through the dry larval skin, it emerges to continue its 

 species ; and under the artificial though favourable con- 

 ditions of plants kept and propagated under glass, numbers 

 of broods emerge in the course of each year. 



Like all other insect " pests," it has its parasites — minute 

 and busy Hymenoptera, quite black in colour, which hover 

 about the infected leaves (Fig. 6), ever ready to attack the 

 larva and insert one of their own eggs in the body of the 

 miner {sei- Fig. 8). 



When the parasitic maggot has reached its full growth 

 (and of course destroyed the maggot of the Marguerite 

 fly) it passes on to the pupa stage within the dried skin of 



FxQ. 5. — Marguerite Fly sealing up|the Egg. ( x 12 Diameters.) 



its host, which is now bleached to a light colour. The 

 enclosed black pupa of the parasite is now a conspicuous 

 object to even an ordinary observer, and care should be 

 taken not to destroy these Mack coloured ones. If growers 

 of Marguerites and other flowers would just note a few of 

 these apparently slight differences, a great deal of good 

 might be done towards increasing these parasites, which 

 are the natural enemies of the injurious maggots. 



Another favourite flower 



mwith everyone, especially 

 Londoners, is the chrysan- 

 themum ; and yet how very 

 few growers, amateur as well 

 as professional, know the fly, 

 Tnjpt'ta chn/santliemi, which 

 is the cause of the mining 

 maggot that excavates be- 

 tween the cuticles, eating all 

 r, „ T TT J ,r J-.. the Ufe away, until the leaves 



FlO. 6. — Larra, Head of ditto, u- •_ i~ i. • i j r ii 



and Pupa of Marguerite Fly. J'^g'." *° '^'?' ^P »°,^ ^^1> 



( X 12 Diameters.) " leavmg the plant totally un- 



fit for exhibition. The finger- 

 and-thumb treatment is the quickest way of destroying 

 the miner, which can easily be felt, if not seen ; but the 

 perfect insect is generally overlooked altogether. I own 

 that it is not a particularly easy one to capture, but it is 

 worth the attempt, as one female is capable of laying a 

 great number of eggs, distributed over one or two dozen 

 plants, and can easily blight all chances of prize-taking at an 

 exhibition. I have noticed the fly all through the summer 

 months, for there are several broods. Before the heat of 

 the day is the best time for observing it, and it is worth 

 observation, as, apart from the advantage of knowing 

 enemies from friends, the fly is an exceedingly interesting 

 one to watch. It is smaller than the ordinary house fly, 

 and of an ochreous colour ; its eyes of the most brilliant 

 shining green, which at certain angles appear golden red ; 

 its wings are ample, with several diffused spots on them. 

 In graceful movements of the wings few ilies can equal 

 this one. The wings are gently raised and lowered 



together, then suddenly one is twisted at a peculiar angle, 

 whilst the insect itself walks round in a circle. Sometimes 

 the wings are allowed to drag along the leaves, after the 

 manner of a strutting turkeycock ; then they are suddenly 



Fig. ".— Ege (Cuticle raised). Part of Mine, and Parasite of 

 Marguerite Fly. ( x 12 Diameters.) 



raised high up together, and the fly seems to take fright 

 and run under cover, only to return and indulge in other 

 strange movements. Should one of the opposite sex 

 approach, these movements are increased, and quite defy 

 description. Those chrysanthemum growers who really 

 wish to capture these flies should use a small net, made of 



Fig. S.— Continuation of Jline and I'lipa of Marguerite Fly, in 

 which Parasite is ovipositing. ( x 12 Diameters.) 



fine book muslin, fixed on a ring of cane four inches in 

 diameter, the net of the jelly bag from about eight to ten 

 inches in length. With a little practice many flies can 

 be caught without injury to the plants. Observation of 

 the mines will soon reveal the parasite peculiar to this fly. 

 {To he continual.) 



Noti(ts of iSooits. 



Electro-Phydology. Vol. II. By W. Biedermann, 

 Professor of Physiology in Jena. Translated by Frances 

 A. Welby. (London : Macmillan ..t Co.) 173. net. We 

 have here a good translation of the second volume of a 

 standard work. The range of subjects treated is the best 

 evidence of the progress which has been made in this 

 branch of science since the inception of the subject by 

 Galvani's experiment in 1790, when, working at Bologna, 

 he observed the curious convulsive movements in the 

 muscles of a recently killed frog when touched at different 

 points by iron and copper which were in contact. The 

 volume before us, beginning with the electro-motive action 

 in vegetable cells, goes on to deal, in separate chapters, 

 with such subjects as the structure and organization of 

 nerve, the conductivity and excitability of nerve, the 

 electrical excitation of nerve, the electro-motive action in 



