芝草を加害する半翅目の害虫に関する研究III

The author studied ecology and course of the prevalence of a turfgrass injuring insect, Rhodesgrass scale (Antonina graminis MASKELL), in the Tokai district for the purpose of controlling this insect. The study is summarized below.<BR>(1) Rhodesgrass scale inhabits in subtropical regions, such as Africa, Australia and the South of the U. S. A., and its habitats in Japan had been restricted in Okinawa Prefecture. This insect is supposed to have lately intruded into Japan along with turfgrass when it was imported.<BR>(2) This insect clings to the proximals of erect branches and nodes of runners of turfgrass and suck the sap of the plant. The injured turfgrass changes its color to brown as it suffered from a drought injury, and withers. The damage is particularly notable at well-drained, sunny, and dry turfgrass-fields and in and after the end of August.<BR>(3) This insect is parthenogenetic and multiplies by ovoviviparity. Embryos in the body of female are milk white, oval, and 0.45mm in length. The 1st-instar insect is not covered with shells and moves actively with 3 pairs of legs. Therfore, it is easy to distinguish the insect of this instar from that of other instars. The length of the insect was 0, 56mm.<BR>(4) The insect of 2nd or higher instars is dark purple in color, takes shape of a bag, extrudes white nephridium outside the body, and inserts its suctorial mouth on the surface of abdomen into the plant, and clings to the plant. The three pairs of their degenerated legs have no locomotive function and serve only to cling to turfgrass. On the turfgrass, the insect excretes white waxy materials to make up the shell. The lengthes of 1st, 2nd, 3rd instars and adults were 0.40 to 0.90 mm, 0.6 to 1.2mm, 1.3 to 1.9mm, and2.0 to 4.0mm, respectively.<BR>(5) As temperature becomes higher, the rate of delivery of larvae is increased. The number of the larvae delivered at the temperatures of 30°C and 26°C were 200 and 139, respectively, with distinct difference by temperature. It would be thought that temperatures higher than 25°C are necessary for delivering larvae.<BR>(6) The time of occurrence of the 1st instar insect was the beginning of June to the middle of July in the 1st delivering stage, and the beginning of August to the middle of September in the 2nd delivering stage. The larvae of the 3rd delivering stage were produced only when the insect had been raised in a glass room, though they were small in number. In the natural state, this insect is considered to develop twice a year.<BR>(7) In order to control the insect in the Tokai district, a desirable effect has been brought about by spraying 1000-time dilution of supracide emulsion in the beginning of June and the beginning of August.