THE PARASITIC FUNGI OF INSECTS. 79 



the blood-cavity of the host, when they become elongated and 

 eventually broken up into long conidia as before. They grow at 

 the expense of the blood of the insect until it is so diminished in 

 quantity and deteriorated in quality that the insect is exhausted, 

 becomes soft and shrivelled, and soon dies. 



As soon as death takes place, these conidia develop into 

 copiously-branching hyphse at such a rate that the caterpillar or 

 pupa regains its original size. A body is thus formed in a day or 

 two retaining the shape of the Hving insect, but consisting almost 

 entirely of a felted mass of mycelium, with some small remains 

 only of the tissues of the unfortunate victim. 



This fungus mass, in the form of an insect, has the power of 

 reproducing the coloured, club-shaped bodies wnth which we 

 started, and this it can do in a few weeks' time, under favourable 

 conditions as to warmth and moisture. If, however, it is exposed 

 to drought and severe cold, it may remain quiescent for months 

 until such time as more favourable conditions prevail. There is, 

 however, an important point to be noticed here. Supposing that 

 these spores do not find a suitable host, when conditions for 

 germination are favourable, they yet have the power of producing 

 the simple conidial spores, which may accordingly be found 

 growing on grass, dead flowers or twigs, decaying furze, etc. ; 

 accommodating themselves, in fact, to a parasitic or saprophytic 

 life, according to circumstances. You will at once see that this 

 simple conidial form corresponds to the Isaria previously men- 

 tioned as formerly supposed to belong to a different genus ; but as 

 a matter of fact it is only waiting the supply of a suitable host to 

 develop into the perfect club-shaped Cordyceps. If no suitable 

 host is found, the simple form probably perishes after a time ; but 

 how long it may last is a matter of uncertainty at present. 



To throw a little light on the life-history of this genus, we may 

 look at that of C. ophioglossoides^ which, however, is not parasitic 

 on insects, but on the truffle. 



The Isaria, or simple conidial form, is perfected early in the 

 season, and is capable of reproducing itself by its own spores or 

 conidia. Later in the season the same mycelium which has pro- 

 duced the Isaria, produces the Cordyceps or perfect fungus, and 

 this, as we have seen, produces asci and filiform spores. These 



