Variation in ovariole number within the Aphidoidea

Several different morphs from over 50 species of aphids were dissected and the number of ovarioles recorded for each. By using these results and published data, details of ovariole number in more than 125 species of aphid from seven families were analysed.

Variation in ovariole number between generations was found in six of the seven families studied. Variation within a generation appeared to be restricted to certain subfamilies.

Certain trends in variability of ovariole number appear to be linked with the morph of the aphid, migratory morphs (particularly within the Aphididae) having greater variability than non-migratory morphs. Heteroecious aphids tend to show greater variability than autoecious aphids which, in turn, show greater variability than anholocyclic aphids.     

Chronic mercury vapor poisoning of aphids

Summary Exposure of green peach aphids,Myzus persicae (Sulz.), to an atmosphere containing mercury vapor resulted in a curtailment ofembryogenesis and larviposition by adults, and in the development by larvae and adults of a cuticular darkening of their legs, head capsule, antennae, cornicles and cauda. Mortality of affected larvae resulted from molting difficulties, particularly by last-instar alatiform female and male larvae. Greenbugs,Schizaphis graminum (Rond.), and pea aphids,Acyrthosiphon pisum (Harr.), responded to mercury vapor exposure in similar ways.     

A new Agriotypus from Burma and redescription of A. gracilis Waterson (Hymenoptera: Agriotypidae)

A new species of Agriotypus Curtis, viz., Agriotypus kambaitensis is described from Burma and the Japanese species, A. gracilis Waterson is redescribed. A key to distinguish the known species of Agriotypus is given.     

The life cycle and natural history of the tropical aphid Cerataphis fransseni (Homoptera: Aphididae: Hormaphidinae), with reference to the evolution of host alternation in aphids

We describe the life cycle and general biology of the tropical cerataphidine aphid Cerataphis fransseni. We demonstrate that this aphid migrates between trees of Styrax benzoin and various species of palms; palm-feeding populations have previously been known as C. variabilis and C. palmae, which now become synonyms of C. fransseni. On S. benzoin the fundatrix induces a relatively simple gall which can contain >6000 aphids at maturity with a large number of reproductively sterile soldiers that protect the gall from predators. These galls are apparently produced throughout the year. Colonies on the secondary host plants, palms, are apparently obligately tended by ants whereas colonies within galls on Styrax are never tended by ants. We discuss the life cycle of this tropical aphid with respect to hypotheses for the evolution and maintenance of host alternation.     

Host-plant oligosaccharins in the honeydew ofSchizaphis graminum (Rondani) (Insecta,Aphididae)

Summary The honeydew of the aphidSchizaphis graminum (Rondani) contains hetero-oligosaccharides (mol. wt>2200 D) having neutral sugar and uronic acid compositions similar to the pectic substances of the host plant,Sorghum biocolor (L.) Moench. These oligosaccharides are pectic fragments which result from the depolymerization of pectic substances in the phloem by aphid salivary polysaccharases.     

Occurrence of sexual morphs in Trama troglodytes von Heyden, 1837 (Hemiptera,Aphididae)

The root-feeding aphids of the tribe Tramini have been cited as a possible case of ancient apomixis, as there are no substantiated records in the literature of a functional bisexual generation, even in common and well-known European species. The karyotypic variation found in this group, involving considerable structural heterozygosity within species, also pointed to the decay of diploidy that would be an expected consequence of loss of sexuality and absence of meiosis. However, we have now found a small number of oviparae (mating females) and males in populations of the common species Trama troglodytes. Fertilized eggs were not obtained, but adult oviparae contained large, yolky eggs. The single adult male was apterous, small and blind, but had fully developed mouthparts and genitalia, and contained mature sperm. Both sexual morphs are described, and the karyotrypic variation is reassessed in the light of these findings. Occasional sexual reproduction is in concordance with recent molecular evidence that some recombination occurs in T. troglodytes and related species.     

新疆石河子8种蚜虫的染色体组型分析

用快速直接染色法对新疆石河子8种常见蚜虫进行蚜虫染色体制片、染色体研究。8种蚜虫染色体数目范围由2n=6至2n=13。根据染色体组型的不同,进行染色体组型分析,为蚜虫的正确鉴定和系统分类提供了参考。     

Possible involvement of the phloem sealing system in the acceptance of a plant as host by an aphid

Possible reasons for the rejection of some lines ofTriticum monococcum (Tm44 and Tm46) by the aphidSitobion avenae were explored. In allT. monococcum lines studied, whether unfavourable (non-host/resistant plant) or favourable (host/susceptible plant), the concentrations of hydroxamic acids, a family of aphid-resistance factors in cereals, were significantly lower than the levels in the favourable host-plantTriticum aestivum cv. Therefore, hydroxamic acids did not account for the host/non-host patterns observed. Phloem sap was collected by stylectomy from young seedlings of favourable and unfavourable plants. In non-aphid-resistant genotypes, the success in stylectomy, the proportion of amputated stylets resulting in long (>1 min) exudations, the average duration of exudation, and the final volume of sap exuded, were higher than in the aphid-resistant genotypes. It is concluded that aphid interference with the phloem sealing system of the plant is a likely mechanism of rejection ofT. monococcum lines Tm44 and Tm46 as hosts byS. avenae.