FUNGUS-DISEASES OF INSECTS. 43 



ants and wood-eating kinds, are infested by hosts of ap- 

 parently harmless microscopic parasites, both animal and 

 vegetable, there are certain species which give rise to grave 

 contagious diseases. Though most of these minute para- 

 sites are vegetable, the common silk-worm is in Europe in- 

 fested by what Balbiani regards as an animal. It is a very 

 minute parasitic Amoeba-like form (called Microsporidinnt 

 bombycis}, belonging, according to Balbiani, to a group 

 called Sporozoa, and allied to the psorosperms occurring in 

 fishes, etc., and to the Gregarinas. The disease produced 

 by this organism is called pebrine, its symptoms being the 

 appearance of black specks on the skin and internal organs, 

 while the blood is filled with the spores of the parasite. 

 This disease, however, is in this country practically un- 

 known, and Forbes believes that it probably cannot be 

 artificially cultivated or propagated in insects related to the 

 silk-worm. 



Of the vegetable disease-germs, the most simple and 

 minute are the Bacteria, Bacilli, and Micrococci, the dis- 

 eases they produce being called " bacterial." The most 

 destructive of these to the silk-worm is variously called 

 flacherie, maladie des O oo <P cPo 



morts-blancs, maladie O o oa^^eto o 



mi 0. r, o&C'C'oooo oo * o^ 



des morts- flats. The *o Q o o 00 



i -, TV- COOccOO OCOOQ) ^JJ 



germ of this disease, ^ OQ O 600, \ <P 



which is called Micro- * 



, 7 i /-< i FIG. 38. Flacherie germs. After Colm. 



coccus bombyc'is by (John 



(Fig. 38), is, like its allies, among the smallest organisms 

 known; it is a microscopic, oval mass of protoplasm, and 

 multiplies very rapidly by self -division, the new individuals 

 often forming chains. In this way a few germs introduced 

 into an insect will multiply with immense rapidity, finally 

 disorganizing the blood and tissues, and causing rapid decay 



Insect Diseases" (Psyche, v., Jan., Fob., 1888, 1). See also Judeicli 

 and Nitsche's "Lehrbuch des Mitteleuropiiischen Forstinsekten- 

 kunde;" the works of Quatrefages and Pasteur on the silk-worm 

 disease; and Balbiani's' " Le9ous sur les Sporozoaires," Paris, 1884. 



