80 THE PARASITIC FUNGI OF INSECTS. 



spores are well protected, being placed within sacs or asci, which 

 again are enclosed in the perithecia, which are themselves 

 embedded in the stroma of the club-shaped end of the Cordyceps, 

 and are thus able to withstand the vicissitudes of winter. When 

 the spring comes, the stroma softens, the mouths of the perithecia 

 open, the asci sail out and burst, and the chains of spores are set 

 free in the air. These chains of spores soon fall to pieces, and 

 each spore, full of vitality, is capable of producing afresh, not a 

 Torrubia, but the Isaria form. How small these spores are may 

 be judged from the fact that, according to Worthington Smith, it 

 would take two hundred millions of them to cover a superficial 

 inch, and that each plant of Torrubia is capable of setting free at 

 least ten millions of these reproductive bodies every spring. 



All the insect-killing species of Cordyceps have the same life- 

 history, including the fungus of Muscardine, the disease of the 

 silkworm caterpillar^ formerly known as Botrytis Bassii. When 

 the spores of this fungus fall on a healthy silkworm, they at once 

 germinate, and in a period varying from 70 — 140 hours (depending 

 on the age of the caterpillar) fresh spores are formed, and the 

 disease is spread from a fresh centre. 



The silkworms do not appear to be diseased, and they eat with 

 avidity ; but they die quite suddenly in a few days. It is very 

 difficult to get rid of the disease from the breeding-houses when 

 once it has broken out in them. The only way is to completely 

 empty the houses and burn the contents, and then disinfect them 

 by the fumes of burning sulphur, washing out afterwards with 

 chlorine water. In spite of all precautions, however, this for- 

 midable disease has greatly reduced the silk-crop in Europe. 



One investigator declares that ne has detected the spores of 

 this fungus in the eggs of Bojubyx ?nori as well as in the different 

 parts of the body of the insect, in all stages of growth. 



Some of the foreign species of Cordyceps are interesting on 

 account of their large size and branched or antlered appearance, 

 the largest species being C. Taylori, found parasitic on caterpillars 

 in New Zealand. 



The vegetating process generally commences from the nape of 

 the neck, from which it may be inferred that the insect in crawling 

 to the place where it inhumes itself prior to its metamorphosis 



