ルリオトシブミ属Euopsから新たに発見された胞子嚢と胞子の揺籃への伝搬方法(甲虫目:オトシブミ科)

Abstract

The mycetangia and the ventral glands are newly discovered in the females of the weevil genus Eupos. The mycetangia containing fungal spores are observed in the metacoxal cavity in 3 places, a membraneous groove between the metasternal process and the metacoxa (Figs. 2, 4, SMa), a fold of the intersegmental membrane between the metasternal process and the venter (Fig. 2, SMb), and a shallow hollow on the hind wall of the metacoxal cavity (Figs. 7, 8, SMc). The last is porose and microsetose (Fig. 10). A few rows of characteristic bifurcate hairs are present along hind margin of the metacoxa (Figs. 5, 6). The females of this genus have special pubescences on the venter, which are arranged transversely in two rows on the first to third ventrites and one row on the fourth ventrite (Fig. 11). Their adjoining pubescences are overlapped at the flattened and undulated apical part (Fig. 15), and large exocrine glands (Fig. 12) open in, a row just behind the front row of the pubescences (Figs. 13, 14, 16). The secreting fluid from the glands may be sucked up into the space between the overlapped pubescences by a capillary action. Before rolling up a cradle, the female cuts the lateral portion of leaf to form a strip at first leaving the upper end uncut, and then “walks around and bites” the strip surface at regular intervals. A mass of spores are observed in these bites made on the strip (Fig. 18) probably due to direct transmission from her mycetangia. When the female rolls up a cradle, she throughly brushes it up with her pubescences for several minutes and cuts it off from the leaf. The fallen cradle gets moldy soon with special fungi, which are whitish in Euops splendidus and lespedezae, or yellowish in E. konoi. These fungi are not yet determined. The mycetangia, ventral glands, erect pubescences, “biting” and “brushing” behaviors are apparently connected with the transmission of the symbiotic fungi to the cradle. These symbiotic organs are absent in the other genera of the Attelabidae and the male of Euops studied.