Completion of diapause in field populations of the cabbage root fly (Delia radicum)

The various diapause and post-diapause stages entered by cabbage root fly pupae during the overwintering period are shown schematically. Although diapause induction started in mid-Aug., the early-pupating insects did not develop further but were maintained in diapause by the warm autumn temperatures. Therefore, diapause development was simultaneous in all Wellesbourne pupae, whether of second or third generation origin. Diapause development started only in mid-Oct., when mean soil temperatures fell below 10°. In the field, 90% of the overwintering population of cabbage root fly pupae had completed pleted diapause by 5 March 1980, 17 Feb. 1981 and 18 Feb. 1982. This was equivalent to a duration of 19 weeks from mid-Oct. onwards, during the winters of 1979–80, 1980–81 and 1981–82 respectively. A further break between the completion of diapause and the warm conditions required to start post-diapause development also helps to condense the emergence of flies in the spring. Hence, an accurate forecast of the time of spring attack by populations of flies similar to those at Wellesbourne should be possible.This study was financed partly by the Commission of the European Communities as CEC Contract No. 0771.     

Preference for plants damaged by conspecific larvae in ovipositing cabbage root flies: influence of stimuli from leaf surface and roots

In laboratory dual-choice assays females of the cabbage root fly, Delia radicum, prefer for oviposition plants with roots damaged by conspecific larvae to undamaged controls. Cauliflower and kale plants were inoculated with root fly eggs (25 per plant) and the hatching larvae were allowed to feed on the roots for various periods of time (1–17 days). After 4 (cauliflower) or 5 (kale) days of larval feeding the oviposition preference was most pronounced and flies laid between 64% and 68% of their eggs near plants with damaged roots. Later, with increasing damage but fewer surviving, and thus actively feeding, larvae, the magnitude of the preference declined. The preference for plants already damaged by conspecific larvae may contribute to the previously observed aggregated distribution of D. radicum eggs in Brassica crop fields.Further experiments revealed that the sensory cues inducing this oviposition preference originate from the complex consisting of the damaged roots, the surrounding substrate (soil) and associated microbes, rather than from the aerial plant parts. In choice assays using the root-substrate complex of damaged and control plants (aerial parts removed), the observed preference for damaged roots was similar to that found for the entire plant but was more pronounced. The damaged roots alone, compared to control roots, received up to 72% (cauliflower) and 75% (kale) of the eggs. By contrast, surrogate leaves sprayed with methanolic leaf surface extracts from the most preferred plants which had been damaged were not discriminated from surrogate leaved sprayed with extracts of the respective control plants. Analysis of glucosinolate levels in methanolic leaf surface extracts revealed that root damage resulted in enhanced concentrations of indole-glucosinolates on the leaf surface in kale but not in cauliflower. Although indole-glucosinolates are oviposition stimulants for the cabbage root fly, the induced changes were apparently too small to influence oviposition behaviour.     

山西省地种蝇属一新种：双翅目：花蝇科

本文记述地种蝇属Ｄｅｌｉａ Ｒ．－Ｄ鞭阳地种蝇新种Ｄｅｌｉａ ｍａｓｔｉｇｏｐｈａｌｌａ ｓｐ．ｎｏｖ．的形态特征,并与近缘种作了比较。     

四川省岷山地区花蝇科泉种蝇属四新种（双翅目;花蝇科）

本文记述四川省松潘县和茂汶县地区花蝇科泉种蝇属４新种,即蝶肛泉肿蝇Ｐｅｇｏｈｙｌｅｍｉａ ｐａｐｉｌｉｏｃｅｒｃａ ｓｐ．ｎｏｖ。巨板泉种蝇Ｐｅｇｏｈｙｌｅｍｙｉａ ａｌｃａｅｃｅｒｃａ ｓｐ．ｎｏｖ。角泉种蝇Ｐｅｇｏｈｙｌｅｍｙｉａ ｃｏｒｎｕｔａ ｓｐ．ｎｏｖ．四尖泉种蝇Ｐｅｇｏｈｙｌｅｍｙｉａ ｔｅｔｒａｃｒｕｌａ ｓｐ．ｎｏｖ。     

Sensory interaction during trap-finding by female onion flies: implications for ovipositional host-plant finding

Using various three-dimensional traps alone and in combination with the onion volatile, dipropyl-disulphide (Pr₂S₂), we found that visual behaviour of female onion flies, Delia antiqua (Meigen), varied with the visual context (background composition and trap spacing) in which traps were presented and the females' reproductive state (mated vs. unmated). Against a background of real onions, females alighted more frequently on spherical than cylindrical traps, and white than green spheres, but females responded equally to white and green cylinders. In an onion field, baiting traps with Pr₂S₂ significantly increased female response to white over green traps, but had no influence on their response to trap shape. When traps were spaced 10 m apart and against a background of bare soil, females orienting to Pr₂S₂ baits alighted more frequently on vertical than horizontal traps, but shape and spectral reflectance were insignificant. However, when traps were spaced 0.25 m apart, females orienting to Pr₂S₂ baits alighted more frequently on cylinders than spheres. Mated females alighted more frequently on green than white cylinders, but unmated females responded to cylinders independent of spectral reflectance. When located 20 m downwind from Pr₂S₂ baits, mated females alighted on green cylinders significantly more often than unmated females. Response to traps mimicking onion plants suggests that ovipositional host-finding in female onion flies is dominated by olfactory responses at long range (several metres) and by visual cues at short-range (ca. 1 m). The view that host location by female onion flies is a hierarchical response pattern mediated by multiple sensory modalities and modified by resource level (habitat) and reproductive status, is discussed.     

四川省花蝇科5种雌性的记述(双翅目:蝇总科)

分别记述采自四川西部山区的小片花蝇(Anthomyia parvilamina Feng,1987)、棘基植种蝇[Botanophila spinulibasis(Liet Deng,1981)]、离叉植种蝇[Botanophila apodicra(Feng,1987)]、缘齿华种蝇(Sinohylemya craspedodonta Hsue,1980)、中华泉蝇(Pegomya chinensis Hennig,1973)等5种花蝇科雌性的模式产地及外形特征。     

Botanophila flies on Epichloë host species in Europe and North America: no evidence for co-evolution

Species of Epichloë (Ascomycota: Clavicipitaceae), which infect grasses, maintain an obligate symbiotic relationship with flies of the genus Botanophila (Diptera: Anthomyiidae). Sexual reproduction of the fungus usually requires a visit by Botanophila, which serves to ‘pollinate’ the fungus with spermatia of the opposite mating type; the flies in turn deposit their eggs on fungal tissues upon which the larvae feed. For a molecular phylogenetic study, a total of 108 fly larvae were collected from 10 different Epichloë species on various grasses in Europe and North America. Sequence analysis of the mitochondrial cytochrome oxidase gene (COII) detected six distinct Botanophila taxa that were associated with Epichloë. Three were restricted to samples from Europe, two to samples from North America, and one was present on both continents. In North America the common taxon [identified as Botanophila lobata (Collin)] was found on Epichloë hosts of native grasses and on Epichloë typhina (Pers.: Fr.) Tul. and Epichloë festucae Leuchtm., Schardl and M.R. Siegel of the introduced grasses Dactylis glomerata L. and Festuca rubra L., respectively. In a maximum likelihood phylogram, one of the American taxa was most basal, while the other was nested within the European taxa, suggesting that European and American taxa of Epichloë-associated Botanophila spp. may not have separate origins. Analyses of the fly populations further indicated that up to four different Botanophila taxa can be present at a single location. On taxon level there was no specificity of flies for Epichloë host species (except taxon 6 that was found only on Epichloë glyceriae Schardl & Leuchtmann), although several taxa appeared to prefer some hosts over others. Comparison of molecular phylogenetic relationships of Botanophila species with those of the associated Epichloë hosts did not suggest co-evolution of the fungus and the fly. Thus, associations between Botanophila flies and Epichloë hosts may have arisen independently more than once.     

The relationship between cabbage root fly (Delia radicum) larval feeding and the freeze-dried matter and sugar content of Brassica roots

Five genotypes of swede (Brassica napus var. napobrassica), two genotypes of kale (B. oleracea var. acephala), and two genotypes of rape (B. napus var. napus) were each inoculated at the 8–10 true leaf stage with five cabbage root fly (Delia radicum) eggs. The percentage pupation after larval feeding on individual plant genotypes ranged from 45 to 78%, and the mean pupal weight from 6.5 to 13.0 mg. After 5 weeks, larval feeding damage had reduced root weight by up to 47%, compared with uninoculated plants. The dry matter content of undamaged roots was higher in the kales and rapes than in the swedes. Whilst the dry matter content of the rapes and swedes were not changed by D. radicum damage, that of the kales was elevated. The ethanol-soluble sugar content of the root was reduced in all cases by D. radicum larval damage. However, the effect of D. radicum damage on the concentrations of individual sugars (glucose, fructose and sucrose) was crop- and genotype-dependent. In the roots of kales and rapes, the glucose and fructose concentrations were either very low or unaffected by D. radicum damage, whilst both glucose and fructose were generally reduced in swede roots by D. radicum damage. The root sucrose concentration was either reduced or not significantly affected by D. radicum damage in all of the crop types tested. The percentage pupation and the mean pupal weight of D. radicum were inversely correlated to root freeze-dried matter content. D. radicum pupal weight was positively correlated with root fructose, glucose and ethanol-soluble sugar contents.     

青海花蝇科一新种（双翅目）

本文记述采自青海省花蝇科泉种蝇属一新种。单锥泉种蝇Ｐｅｇｏｈｙｌｅｍｙｉａ ｍｏｎｏｃｏｎｉｃａ ｓｐ．ｎｏｖ．模式标本保存在中国科学院上海昆虫研究所。