23063

Unrefereed

0368-6264

AN0005519X

In order to secure their lives, all the larvae of the tube renter Hymenoptera (solitary bees and wasps), in a given nest, must face to the exit of the nest when they pupate in their own cells. If not, the adults of the next generation can not emerge safely from the nest in which they were bred. They will be able to find out the exit only when they moved forward in the nest which is just large enough for the linear (forward and backward) movements of the adults. Figs. 1 and 2 will explain clearly this statement. Therefore, the factors influencing on the orientation of pupa or cocoon in a given cell is very significant to those bees and wasps, or even to the species which nest in the ground, too. For the tube renters whose nests are kept horizontally in nature, I have described and illustrated in this paper the positive orientation of pupae (cocoons) in the nests of Megachile sculpturalis (Figs. 1-2), Coelioxys fenestrata (Figs. 3-4), Trypoxylon obsonator (Figs. 5-9), Trypoxylon sp. (Figs. 18-21), Sphex nigellus (Figs. 22-24), Ammophila aemulans (Figs. 29-34), Odynerus sp. (Figs. 35-37), and Anterhynchium flavomarginata micado (Figs. 38-39). In regard to their cells, the material used for the cell partitions differs from species to species. For example, Megachile sculpturalis makes use of the resin for their cells, but Trypoxylon obsonator provides the cells with the mud partitions. In any case, however, one end of the cell partition is smooth-concaved, and the opposite side is rough-convexed as a result of the labor of the nesting adults which enter and work in the nest from one way only. In consequence, the cell is provided with the smooth-concaved and rough-convexed partitions. The very combination of these partitions is responsible to the positive orientation of the pupae or cocoons of the tube renters. This was first assumed by Yasumatsu in 1929 for Trypoxylon obsonator, and confirmed by me in 1958 based on a series of experiments on Osmia excavata and O. pedicornis. Present observations on the species mentioned above may be supplementary to our theory. Another interesting orientation of pupae (cocoons) in Trypoxylon obsonato r was observed when the cell was kept vertically. My experiment and the result is shown in Figs. 10-13. This sort of positive orientation was demonstrated by me in Osmia excavata already. Thus, the larvae of these two species are proved to be very responsive to the partitions, especially to the smooth-concaved condition of them, in a given cell. This is one of the expressions of their high adaptability of their lives. In regard to the soil-nesting solitary Hymenoptera, only the bees were discussed in this paper, because the cells of them are highly specialized. Their shape are pot-like, and the interior is smooth and nearly polished. This is probably because the nesting adults have to store the pollen ball or honey cake in the cells for their larvae. I have discussed and illustrated the cells of Lasioglossum affinum (=Halictus affinis) (Figs. 40, 41), Rhopalomelissa esakii (Fig. 42), Nomia punctulata (Fig. 43), and Tetralonia mitsukurii (Figs. 44, 45) in this paper. In such species like Lasioglossum affinum and Rhopalomelissa esakii, the cells are situated nearly horizontally in the ground. Full-grown larva of these species rests on the back when pupate, with its head closer to the exit of the cell (namely, positive orientation), on the bottom of the cell which is slightly concaved. To this orientation of pupa, interestingly, the feces-excreting habit of the larva is closely associated. This is illustrated in Fig. 41. In addition, Lasioglossum affinum is a unique species whose larvae secrete the sticky silk-like threads while they excrete (Hirashima, 1960). In such species like Nomia punctulata (Fig. 43) whose cells are vertical , the prepupae stand naturally in their cells (positive orientation), because the cells are just large enough for them. They do not stand up-side down because of the antigravity character which is extensively shared in the bees and wasps. Some examples of the antigravity character are shown in Figs. 14-17 for Trypoxylon obsonator, in Figs. 25-28 for Sphex nigellus, and in Fig. 45 for Tetralonia mitsukurii. The last named species is interesting, in spite of its soil-nesting habit, in that the larva makes cocoon when pupate. Note the position of feces in this species (Fig. 45).