T4 THE PARASITIC FUXGI OF INSECTS. 



a separate position. The members of this group, though parasitic, 

 do not appear to be particularly harmful to their hosts as a rule. 

 They are generally found on the elytra and outer surfaces of 

 beetles, which live either in or near water ; one species, however, 

 is found affecting the common house-fly. 



The usual appearance is that of small brown brushes studded 

 over the surface of the insect, but sometimes these grow so close 

 to one another as to give the appearance of the insect being 

 enclosed in thick fur. 



Each plant consists of a filiform, or club-shaped stalk, support- 

 ing a conical or flask-shaped body (the perithecium), which 

 contains a variable number of spore cases (asci), and each of these 

 in its turn contains from eight to twelve spores. Attached to the 

 base of the perithecium is a peculiar filamentous body, called the 

 appendage, the use of which is not known. 



The ripe spores are fusiform, colourless, and bi-cellular ; they 

 are liberated by the gelatinous deliquescence of the wall of the 

 ascus, and escape through the orifice of the perithecium. 



The spore, on its escape, attaches itself by one extremity to 

 the chitinous covering of the insect, and sends into it a small 

 short tube, which sometimes enlarges into a knob at its extremity. 

 Thus firmly planted, it develops at right angles to its basis, and 

 eventually reaches its mature state by the necessary successive 

 cell divisions and differentiations. 



There is no mycelium, but the spores, being very small and 

 very numerous, are easily conveyed from one insect to another. 

 This is as much as is known of the life-history of this fungus, 

 which is entirely confined to the external surface of the body of 

 the insect, and does not seem to be detrimental to the health of 

 the host. 



Entomophthore^. 



The fungi of this group differ from the last in several ways. 

 They seem more allied to the Mucorini than to the Ascomycetes, 

 and they are much more destructive to their hosts, for they 

 penetrate into the cavities of the bodies of living insects, and 

 there develop. There are two principal genera of this group— viz., 

 Empusa and Entomophthora. In the Empusse numerous 



