. Minnesota plant diseases. Plant diseases. Fig. 47. — An insect mold. (Fly chol- era fungus.) 1. A cluster of threads with spores cling- ing to hairs on the insect's body. 2. Fungus threads from the fat-body of an insect. 3. Spore -bearing threads, highly m a g n i fi e d. 4. Above, a single spore; below, germinating spore, forming a sec- ondary spore. Highly magnified. After Brefeld. are sent into the threads of the host plant where they obtain nourishment for the para- site. They are also found on certain of the blue-mold group of fungi. Insect molds {EntomophthorinecE). Of all the algal fu
. Minnesota plant diseases. Plant diseases. Fig. 47. — An insect mold. (Fly chol- era fungus.) 1. A cluster of threads with spores cling- ing to hairs on the insect's body. 2. Fungus threads from the fat-body of an insect. 3. Spore -bearing threads, highly m a g n i fi e d. 4. Above, a single spore; below, germinating spore, forming a sec- ondary spore. Highly magnified. After Brefeld. are sent into the threads of the host plant where they obtain nourishment for the para- site. They are also found on certain of the blue-mold group of fungi. Insect molds {EntomophthorinecE). Of all the algal fungi these are most clearly non- aquatic in their habits. Like the black molds they form breeding spores, from similar sex organs, though these spores are not of fre- quent occurrence. On the other hand the non-sexual spores are very abundant and are pinched off from the ends of special threads. Moreover, there is usually some de- vice for throwing the spore to a distance. The thread is swollen just below the spore and when the latter separates from the thread the release of pressure in the swollen portion results in the forcible ejection of the spore. This is the case in the common fly cholera fungus. Most of the insect molds are para- sites on insects either in the adult stage, as in the fly cholera, or on the larva. When the fungus has gained entrance to the body of the insect it soon kills the latter and then lives saprophytically, pro- ducing a great abundance of spores. House flies are commonly attacked by fly cholera in autumn and when they die cling tightly to window panes and other objects. They are soon surrounded by a halo of spores thrown onto the pane from the fungus threads by means of the spore-throwing device described above. Many other insect diseases are caused by these fungi. Caterpillars some- times become covered with moldy growths which completely envelop them. From the surface of these growths are thrown the fungus spores. These parasites of insects prov
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