384 PHYSIOLOGY OF THE FUNGI 



tional requirements of these fungi, since very little is known. We may 

 assume that rather specific nutritional needs, either for growth or for 

 reproduction, are satisfied by the relation with insects. 



Among the fungi parasitic on insects the genus Entomophthora is the 

 most common. Various common species attack houseflies, grasshoppers, 

 and other insects. A direct correlation between the amount of precipita- 

 tion and the number of infections on houseflies was reported by Yeager 

 (1939). Massospora cicadina infects the seventeen-year cicada and 

 produces spores inside the abdomen. The posterior portion of the abdo- 

 men sloughs away, exposing the spores w^hile the insect is still able to crawl 

 about. This is apparently the chief method of dissemination of the 

 spores. The mode and time of infection are unknown. Species of 

 Cordyceps are common on pupae and larvae of certain insects. The fact 

 that C. militaris produces abundant mycelial growth on a variety of 

 synthetic media in the laboratory suggests the possibility that in nature 

 this fungus may grow on other substrata, requiring the insect association 

 only to fruit. 



Fawcett (1910) described the use of a fungus, which he named Aegerita 

 webberi, in controlling whitefly in the orange groves of Florida. Ascher- 

 sonia aleyrodis has also been used for the same purpose. A chytrid, 

 Myrophagus ucrainicus, is reported (Karling, 1948) as a parasite on scale 

 insects in Bermuda, Louisiana, and Ontario. In severe outbreaks as 

 many as 45 per cent of the female insects may be killed. It has also been 

 transmitted to mealy bugs. Another group of fungi parasitic on insects 

 is the Laboulbeniales. These are minute fungi developing almost entirely 

 on the surface, sending short haustoria into the insect to obtain food. 



The symbiotic relationship between Septobasidium and scale insects 

 is interesting because of the high degree of specialization on the part of 

 the fungus (Couch, 1938) . The dependence of the fungus for its distribu- 

 tion upon the migrating young scale insects was previously mentioned in 

 Chap. 15 under Spore Dissemination. The fungus forms a crust over 

 scale insects, some of which are parasitized while others are not. The 

 uninfected females give rise to young insects, which may remain under 

 the fungus crust, crawl out through tunnels under the fungus, or crawl 

 out over the sporulation surface of the fungus. The young insects are 

 infected only by the bud cells from the basidiospores, never by the older 

 fungus hyphae. The bud cells germinate on the surface of the insect and 

 apparently enter principally through the natural openings. The fungus 

 then produces coiled haustoria, which absorb food directly from the 

 circulatory system of the insect, which in turn sucks its food from the 

 host tree. Some infected insects may settle down on the bark, while 

 others crawl under a nearby protective fungus colony. Only the former 

 are responsible for distributing the fungus, while the latter are responsible 



