Two New Species of Hirsutella Patouillard

Abstract

During the summer and fall of 1948, epizootics were observed of two economically important arthropods, rust mites [Phyllocoptruta oleivora (Ashm.) ] and purple scales (Lepidosaphes beckii Newm.), on Citrus in Florida. The occurrence of a fungus consistently associated with dead first instar nymphs of purple scales was reported by Fisher et al. (2), and tentatively identified as a species of Hirsutella. Later, a fungus on dead rust mites was also reported (1) as probably being Hirsutella sp. Further study has shown that these fungi on dead rust mites and dead first instar nymphs of purple scales are not only separate and distinct species, but also are species which have not previously been described. Both of these fungi are easily recognized under a dissecting microscope with a magnification of 15 X. On young purple-scale nymphs, the Hirsutella exhibits an extensive growth of mycelium which originates from the ventral surface of the insect's body. Only a few hyphae are present on rust mites; these hyphae typically extend posteriorly or anteriorly from the mite's body, but, occasionally, lateral hyphae are found. The direction of the mycelial growth depends upon the portion of the mite's body from which the hyphae emerge. For instance, if a hypha emerges from the posterior region of a rust mite's body, the typical growth of that hypha will be a direct extension posteriorly from the body. Since the larger-bodied scales give rise to a fuller mycelium than do the smaller-bodied mites, the variations between the two species were at first considered to be non-specific and to be directly related to the food supply. It has been found, however, that the dissimilarities betwreen these two species are not only in size and extent of mycelium, but also in the shape of the phialides and the spores, and the color of the older mycelia. 290