NATURE OF FUNGI. q 
nourishment by means of a mycelium from the matrix,’’* there 
are exceptions to this rule with which the majority accord. 
Of the fungi found on animal substances, none are more 
extraordinary than those species which attack insects. The 
white mould which in autumn proves so destructive to the 
common house-fly may for the present be omitted, as it is 
probably a condition of one of the Saprolegniei, which some 
authors include with fungi, and others with alge. Wasps, 
spiders, moths, and butterflies become enveloped in a kind of. 
mould named Jsaria, which constitutes the conidia of Torrubia, 
a genus of club-shaped Spherie afterwards developed. Some 
species of Isaria and Torrubia also affect the larvee and pupx 
of moths and butterflies, converting the whole interior into a 
mass of mycelium, and fructifying ina clavate head. It has 
been subject for discussion whether in such instances the 
fungus commenced its development during the life of the in- 
sect, and: thus hastened its death, or whether it resulted after 
death, and was subsequent to the commencement of decay.t 
The position in which certain large moths are found standing 
on leaves when infested with Jsaria resembles so closely that 
of the house-fly when succumbing to Sporendonema Musce, 
would lead to the conclusion that certainly in some cases the 
insect was attacked by the fungus whilst still living; whilst in 
the case of buried caterpillars, such as the New Zealand or 
British Hepialus, it is difficult to decide. Whether in life or 
death in these instances, it is clear that the silk-worm diseasc 
Muscardine attacks the living insect, and causes death. In the 
case of the Guépes vé,étantes, the wasp is said to fly about with 
the fungus partially developed. 
In all fungi we may recognize a vegetative and a reproductive 
system: sometimes the first only becomes developed, and then 
the fungus is imperfect, and sometimes the latter is far more 
prominent than the former. There is usually an agglomeration 
of delicate threads, either. jointed or not, which are somewhat 
analogous to the roots of higher plants. These delicate threads 
* Berkeley’s ‘‘ Introduction to Cryptogamic Botany,” p. 235. 
+ Gray, ‘‘ Notices of Insects which form the Basis of Fungoid Parasites,” 
