76 THE PARASITIC FUNGI OF INSECTS. 



The whole strength of the protoplasm is expended in forming 

 the spores, so that the mycelium within the body of the insect 

 shrinks and disappears, and at last there is left only a shrivelled 

 and dried mummy. 



The reproductive process described both in the case of 

 Empusa and Entomophthora is a purely vegetative, or asexual 

 one ; there is another, or sexual process sometimes observed. 

 The cells of adjacent tubes of mycelium develop an H -shaped 

 union by means of the necessary processes, and establish an open 

 communication at the point where the processes are in contact 

 with one another. Then a spherical protuberance appears near 

 the point of union, which gradually receives the entire protoplasm 

 of the conjugated cells, becomes isolated by a membrane, and finally 

 forms the zygospore, or resting spore. This in due time emits 

 a short tube, the promycelium, which forms conidia in the manner 

 previously described. Sometimes also parthenogenesis takes 

 place — />., there is no formation of antheridial or male branches, 

 yet the resting spore is produced just the same. 



In all this we have some resemblance to the life-history of 

 fungi parasitic on plants and also to that of Saprolegnia ; but here 

 I have to retract some observations which I made in my paper on 

 Saprolegnia some years ago.* In that paper mention was made of 

 a supposed genetic connection between Empusa and Saprolegnia ; 

 but in the light of recent investigation it is found that Empusa 

 does not develop into Saprolegnia on any occasion, and the state- 

 ment may be, in fact, placed in the romance of mycology. 



The Entomophthoreae are parasitic on numerous insects, and 

 as such serve a very useful economic purpose in nature in the 

 destruction of noxious insects. For instance, locusts are rapidly 

 attacked by these fungi, and so certain and rapid is the course of 

 development that death results in about twenty-four hours after 

 the first indication of the attack. 



One species, E. Planchofii^ attacks the aphis, and in connec- 

 tion with this a very interesting point has been raised — viz., 

 whether this special parasite of the aphis might not be got to prey 

 upon the phylloxera, the great destroyer of the vines. Experi- 

 ments tried with this view have so far been unsuccessful ; but it 

 would be a great thing if a destructive agent like this could be 

 converted into a powerful auxiliary of agriculture. 

 * '^^Q Journal of Microscopy^ 1883, p 185 



