Population dynamics of the whitebacked planthopper,Sogatella furcifera (Hemiptera: Delphacidae) with special reference to the relationship between its population growth and the growth stage of rice plants
A population census was conducted to describe the effects of the growth stage of rice on the population dynamics ofS. furcifera, in particular, on immigration, seasonal abundance, population growth rate, and wing-form expression. The number of immigrants was highest on rice plants 17 to 30 days after transplanting (DAT), which suggested that immigrants prefer to settle or remain more on rice plants at the tillering stage (approximately 20–30 DAT). Population growth rate from immigration to the 1st generation decreased with an increase in rice plant age. In contrast, population growth rate from the 1st to 2nd generation was not influenced by rice plant age and was negatively density-dependent. The percentage of macropters (flyers) was positively related to the growth stage of rice when rice was in the vegetative or early part of the reproductive stage, and reached 100% at about 10 days before heading (booting stage). Threafter, most adult females molted into macropters regardless of population density. The roles of host plant age and crowding effect on the population dynamics ofS. furcifera are discussed.
Studies on the Polymorphism in the Planthoppers (Homoptera, Araeopidae)
トビイロウンカ,セジロウンカ,ヒメトビウンカについて,いろいろな形質の翅型による差を調べた。1) 形態的形質についてみると,前,後翅とも長翅型は完全で,短翅型は短く,不完全な発育しかせず,後翅はまったく痕跡的である。小楯板にも同様の差がみられ,長径においてその差がはっきりしている。2) 後脚の長さ,産卵管長では逆に短翅型のほうが大きく,羽化直後および産卵期間中の平均体重でもこの傾向が見られ,翅を除く一般的体型においては短翅型が大きいと考えられた。3) 総産卵数は個体による変化が大きく,翅型による差ははっきりしない。同様に成虫寿命においても差ははっきりしないが,産卵期間中の平均体重などとともに考えれば,やや短翅型のほうが,産卵数においてもまさるようである。個体ごとにみて,産卵数と寿命の間にははっきりした正の相関が見られる。4) 産卵前期間では,短翅型のほうが明らかに短く,低温によってもあまり延長しないが,長翅型では低温によって大きく延長する。5) 羽化後,水以外の食物を与えず寿命を調べたところ,雌雄とも長翅型のほうが明らかに長い。6) 羽化後毎日体重を測定したところ,短翅型ではすぐに体重増加が見られるのに対し,長翅型では1∼2日おくれる。これによって産卵前期間の差が生ずるものと思われる。羽化直後から産卵開始までに体重は70∼80%増加する。産卵開始後も平均値を中心に20∼30%の範囲内で上下に変動しながら産卵を続ける。雄では体重の変化はほとんどない。7) 短翅型-長翅型関係をadult-jevenile関係とみなして,それぞれのもの適応的意義について論じた。
Relation between Leafhopper Influxes and Synoptic Weather Conditions.
Abstract A study was made of the association of potato leafhopper influxes into Illinois with existing synoptic weather conditions. With data for 25 observed influxes during 1951–59, synoptic weather maps and climatological records were studied to obtain information during and preceding the flights on: wind conditions between the Louisiana source region and Illinois; the presence of fronts in Illinois; the extent and intensity of rainfall in the state; and prevailing temperature conditions. Results of the study indicated a strong relationship between synoptic weather conditions and leafhopper influxes. Typical meteorological conditions favoring influxes were found to be: a persistent southerly flow of maritime tropical air from the Gulf states into the Midwest for at least 36 hours prior to the Illinois influx; rainshowers or thundershowers on the days of influx; and, the presence of a front, usually a cold front, at the time of the recorded influx. From the above criteria, days favorable for influxes dur...