KNTOMOl'IITIIORKAK OF THE UNITKI) STATES. 



Ill 



arc such as are represented in figs. L06 L08, while fig. 127 shows examples of those 

 which precede the spore formation and are derived from them. Tn other cases, the ulti- 

 mate hyphal bodies may he very irregular in size and shape. In all instances, they contain 

 a highly concentrated fatty protoplasm and are capable of subsequent and often very 

 extended development. 



Having reached this condition by the production of a mass of hyphal bodies, the fun- 

 gus, under favorable conditions of temperature and moisture, may proceed at once to 

 the completion of its development; but if these conditions are absent, a resting or 

 chlamydosporic condition supervenes, in which the contents of each hyphal body be- 

 come surrounded by a single wall of variable thickness according to the duration of 

 this enforced resting stage. In this manner, the fungus may remain dormant for a 

 considerable period until the presentation of proper conditions for further growth. How 

 long the chlamydospores may live, I am unable to say; but I have observed their germi- 

 nation after several weeks, and they probably retain their vitality for a much longer 

 period, and may perhaps hibernate under certain circumstances. They form a very con- 

 venient means for the cultivation of Empusae in water, in which they proceed at once to 

 the formation of conidia or of resting spores. The period from first infection to the 

 formation of chlamydospores or hyphal bodies, prior to the commencement of the repro- 

 ductive growth, varies according to the host. In very minute and ephemeral insects, 

 such as many gnats that are commonly attacked, the period must necessarily be short, 

 not exceeding two or three days; but in cases where I have been enabled to observe this 

 period, which has been unfortunately only in connection with the larger hosts, such as 

 flies and caterpillars, it varies from six to twelve days. 



Germination of the hyphal bodies and chlamydospores. — Having appropriated the 

 whole or the greater portion of the nourishment afforded by the host, the fungus is now 

 ready to expend it in the second or reproductive stage of its growth. Under the influ- 

 ence of a moist atmosphere and a sufficiently high temperature, the hyphal bodies 

 "germinate" with great rapidity. The amount of moisture needed to produce this ger- 

 mination is variable in different forms. In the common house-fly fungus (E. muscae), 

 for instance, a slight change in the amount of atmospheric moisture is sufficient to pro- 

 duce conidial formation and discharge. This is very noticeable on the seashore, where 

 slight changes of the wind on or off the water produce a very rapid and noticeable ef- 

 fect upon flies thus parasitized when observed in the ordinary atmosphere of the house. 

 In other instances, more especially in those species which, unlike the house-fly fungus, are 

 characterized in their conidial reproduction by a considerable external growth of hyphae, 

 a much greater degree of moisture is a necessity. Extreme cases of this kind are found 

 in species such as E. conica or E. sepalchralis which occur only in very moist situa- 

 tions. 



In germinating, each hyphal body or chlamydospore sends out one or more hyphae which 

 grow with great rapidity; but the manner of this germination, together with the subse- 

 quent development of the resulting hyphae, varies considerably in different species and 

 under different condition. In the simplest case a single hypha thus produced may grow 

 directly to the outer air and then produce a single conidium or set of conidia, according 

 to the type peculiar to its conidiophores. In other cases, a single primary hypha may 



MEMOIRS BOSTON SOC. NAT. HIST., VOL TV. 21 



