BREEDING BIOLOGY OF THE DARTFORD WARBLER SYLVIA UNDATA IN ENGLAND

The breeding biology of Dartford Warblers was studied during 1975–1976 in 1010 ha of heathland on the Purbeck peninsula, Dorset; comparisons are drawn from other areas of the species' range. Clutches were of 3,4 or 5 eggs, with the mean clutch size increasing progressively from early May to mid-June, declining thereafter. Incubation and brooding of the young were shared unequally between the sexes, with the female taking the greater part. In the number of feeding visits to nestlings there was no difference between the sexes until the last four days of nest-life, when the male greatly increased his share. Nesting was comparatively successful (about 80% of nests producing some young), though the incidence of single infertile eggs was high. There were large variations between years and sites in the timing of the starting of laying. Late-laying pairs reared only one brood, while early starters could rear two. Timing of starting, influencing the number of broods reared, appeared to be the most important factor causing variation in breeding productivity. No vegetational characteristics were entirely adequate to explain variation in starting dates. Past data, however, showed earlier starting in Sussex and Jersey where gorse was a more abundant component of the vegetation of Dartford Warbler habitat than in Dorset. It is suggested that the abundance of gorse is directly related to the quality of the habitat for Dartford Warblers, and hence to breeding productivity.     

THE IDENTITY OF THE SWEDE MIDGE, WITH NOTES ON ITS BIOLOGY

A brief historical summary is given of the literature concerning Contarinia nasturtii Kieffer, C. torquens de Meijere and C. geisenheyneri Riibsaamen, three gall midges (Cecidomyidae) which have been associated respectively with leaf damage on Brassica spp. in England, identical malformation on the Continent and swollen and closed flowers of Brassica spp. in Europe.
Following the discovery in England of the true Contarinia nasturtii causing swollen and closed flowers oiRorippa amphibia, preliminary experiments have shown that midges from this source will also cause similar damage to swede flowers and that they are the same species as those attacking R. amphibia blossom in the Netherlands.
Further preliminary experiments have shown that swede midge derived from rape leaf axils will also cause identical damage to radish flowers in addition to breeding successfully on the leaves of turnip, swede, cabbage and radish.
Male midges derived from Rorippa blossom have been mated with females from rape leaf axils, and their offspring have been reared on Rorippa flowers and on turnip leaves.
This biological evidence confirms the previous supposition based on morphological grounds that the swede midge is Contarinia nasturtii Kieffer and will cause either flower or leaf damage. Consequently, C. torquens de Meijere and C. geisenheyneri Riibsaamen must remain synonyms.
The shortest time for a generation (from parent to first offspring midge) to develop was 24–39 days in an unheated open glasshouse during June-July in 1949 at Harpenden. Under the same conditions, the shortest time for the next generation from late July to August was 29–32 days. C. nasturtii is the first Contarinia species in which unisexual families have been discovered.     

稻瘿蚊的天敌黄柄黑蜂个体发育及其生物学

黄柄黑蜂是稻瘿蚊的群居内寄生天敌,常产卵二、三堆在寄主卵或初孵幼虫体内,每堆卵10多粒,每粒卵发育为一个体,是属单胚繁殖。卵梭状,长15微米,宽6微米。卵母细胞两次成熟。在日平均温度29.5℃下,卵核第一次分裂形成纺锤体大约在产卵后10—12小时,第二次分裂形成纺锤体约在产卵后24小时。在产卵后48小时,两个极体在卵的前端合并为极核,雌性原核和雄性原核在卵的后端合并为分裂核。产卵后2.5天,卵粒长大,此时称为寄生体,胚区及包围它的滋养羊膜形成。当寄生体发育至第4天,副核团分裂一大一小两块占据卵的前端。寄生体发育至5—6天,就变为圆形,胚核由一个分裂为2个、4个。卵产后8天,囊胚层形成。产后10—13天,寄生体长达300微米,宽192微米。卵期13—14天。幼虫期仅3天。蛹期8—10天。在一寄主内能发育9—61头黄柄黑蜂。雌蜂具有避免在同一寄主上重复产卵的本能。雌雄性比为8:1。每年发生8代,以早期胚在稻瘿蚊1龄幼虫体内越冬。     

菊花组织培养过程的光质效应初探

光质在菊花组织培养过程中具显著的生物学效应。试验中,绿色光可促进试管菊的生长,绿色、红色、兰色光还能部分解除~(60)Co—γ射线照射试管苗后所产生的抑制生长作用,红色光有利于花瓣愈伤组织的形成。菊花组织培养过程中的光质效应,尚与品种有关,表明品种间存在光质敏感性的差异。     

STARFISH DIVERSITY IN THE WENLOCK OF ENGLAND

Abstract: Although their record extends back to the Early Ordovician, the occurrence of fossil starfish (Echinodermata: Asteroidea) is dependent almost exclusively upon horizons of exceptional preservation. Thus, asteroids found in Silurian obrution deposits of the English Midlands and Welsh Borderlands are particularly significant to an understanding of the early diversity of the group. Six species are described here: Hudsonaster? carectum sp. nov. (Hudsonasteridae), from the lower part of the Lower Elton Formation; and, from the Much Wenlock Limestone Formation, the hudsonasterids Doliaster brachyactis gen. et sp. nov. and Siluraster? ketleyi (Spencer, 1916), the lepidasterids Lepidaster grayi Forbes, 1850 and Lepidactis wenlocki Spencer, 1918, and the palasterinid Palasterina orchilocalia sp. nov. Though few in number, they show a diverse range of body morphologies when compared with Ordovician taxa: L. wenlocki had long, slender rays when fully grown whereas D. brachyactis is the first asteroid with the short‐rayed body form of extant cushion stars. Most distinctive of all is L. grayi, the earliest multiradiate taxon known, all complete specimens of which have 13 rays. This morphological variety is interpreted as indicating that by the Early Silurian starfish were exploiting a wide range of feeding habits and ecological niches.