66 THE HOUSE FLY— DISEASE CARRIER 



They contain usually a large oil globule and are sur- 

 rounded after discharge by a mass of protoplasm. 



If the conidium when discharged has come in con- 

 tact with a suitable host insect, it adheres to it and sends 

 out a hypha of germination which enters its body as 

 just described. Secondary conidia are formed as a 

 provision for further dissemination in case the primary 

 spore has fallen on a substance unsuited to its proper 

 development. With Empiisa mvisccc the secondary con- 

 idia are like the primary, or more commonly they are 

 sub-ovoid, small, round at the apex, and formed by 

 direct budding from the primary form. These also are 

 discharged, but are apparently better suited to resist 

 unfavorable conditions than the primary ones, and 

 probably retain their power of germination much 

 longer. 



There is also another morphological character of 

 these fungi — the formation of simple hyphse which pro- 

 ject out beyond the conidiophores. When they reach 

 in the direction of the material upon which the de- 

 stroyed insect stands they attach the body to it, and 

 are then called rhizoids. When they stick out in any 

 other direction, however, they seem to be functionless 

 and are called cystidia or paraphyses. The hyphae of 

 attachment or rhizoids may be simple or variously 

 branched, and their germination may be variously 

 modified into an extended sucker. They do not seem 

 to enter into soft substances, and their adhesion is ap- 

 parently due to the presence of a viscous secretion. 

 They are produced with great rapidity, appearing often 



