The sub-order Isariacei has four genera found on the pupæ of moths, on dead spiders, dead fungi, and dead plants respectively. The group is characterized by compound threads ending in pulverescent spores. Most of the caterpillars of the Bombyx Rubi, or bramble moth, fall victims to a species of Isaria, which has several distinctly different periods and modes of fructification, and at last assumes the form of a very beautiful fungus belonging to a different family. Near Paris, in the month of October, when the caterpillars of the bramble moth seek for shelter from the cold, in the earth, or under long grass and withered leaves, M. Tulasne and his brother found that most of them were surrounded by tufts of a whitish down, which increased so rapidly that it killed the caterpillars and covered the whole of their body except the bristly hairs, and assumed characters similar to the muscardine fungus that kills the silkworm. This down is a mycelium composed of extremely fine branched filaments felted together, the upright fertile branches of which bear whorls of branchlets each terminated by chaplets of from ten to fifteen equal and spherical cells filled with dust spores. These most minute spores germinated, and put out filiform creeping germs which quickly emitted many branches ending in long chaplets of fertile dust-bearing cells. Points here and there on the felted envelope of the caterpillars became of an orange colour, took the form of a mycelium, and produced little orange coloured club-shaped cells which shed abundance of reproductive dust spores from a ring of white hairs on their summit. Each caterpillar had from ten to fifteen of these coloured clubs on its sides, which lost their brightness when they grew old, and had shed their dust spores. These fungi possessed all the characters of the Isaria crassa, or Isaria farinosa of Fries. Later in the season other caterpillars on which this club-shaped Isaria had not been produced, but which were swollen and white with the felted spawn of the parasite, gave out orange red club-shaped vessels of a larger size and deeper tint than those of the nascent Isariacei. They had no terminal ring of hairs, but some of them had a red spore dust-bearing felt at their base. Ultimately they assumed all the characters of the Sphæria militaris of Ehrenberg or Cordyceps militaris of Fries, which is a bright scarlet fungus half an inch high with a fleshy upright stem ending in a cup-shaped head containing long cylindrical sacs called asci, in which the spore cells are so numerous as to resemble strings of beads.[55] This fungus, therefore, begins as a member of the family Hyphomycetes, and ends as a member of the family Ascomycetes. The order Stilbacei are little globose fungi with or without a stalk, covered with semi-gelatinous spores. They are united in cushion-like masses, on decayed wood and dead twigs. The little scarlet masses on dead currant branches so often seen in gardens, are examples.