Showing papers on "Lasius published in 1991"

Rareness of certain Mediterranean ant species: fact or artifact?

Abstract: A checklist of the ants recorded during five years in a small urban area (400 m2) in Sant Cugat (Barcelona, Spain) is presented. 23 species nest in the area, 7 species (hypogaeic or parasitic) probably nest and 5 species nest in the vicinity; five additional species have also been recovered from the area. The rarity of some of these (Leptanilla sp.,Hypoponera abeillei (Emery),Cryptopone ochraceum (Mayr),Smithistruma tenuipilis (Emery),Epitritus argiolus Emery,Trichoscapa membranifera Emery,Chalepoxenus muellerianus (Finzi),Anergates atratulus (Schenck),Plagiolepis xene (Schenck),Lasius carniolicus Mayr) and the high number of species suggest that a) rarity in Mediterranean ant species may be explained by the insufficient sampling in time of adequate microhabitats (hypogaeic species) or by the inconspicuousness of social parasitic species, and b) that previously published species lists of ants from Mediterranean habitats might be rather incomplete.

Studies on the relationship between the ant ectoparasite Antennophorus grandis (Acarina: Antennophoridae) and its host Lasius flavus (Hymenoptera: Formicidae)

Abstract: The mite Antennophorus grandis (Berlese, 1903) is a large obligate ectoparasite of workers of the ant Lasius flavus(Fabricius). It rides under the head of the ants and uses its long front legs to communicate with its hosts and stimulate them to give it food. We present allometric and morphometric data showing that L. flavus workers can occur in two size classes. We also present the first quantitative ethograms of mite-bearing and mite-free L. flavus workers of the two size categories. The mites tend to occur on the smaller nurse workers and receive food from them at an extremely high frequency. Antennophorus grandis also frequently gain food when one ant is donating food to the one they are riding upon. The mites seem to inhibit the ability of their host worker to show most social behaviours such as tending ant larvae. The mites frequently move from one host worker to another. For these reasons the mites may have a larger impact upon their host colony than their relative rarity first suggests. The ants do not seem to have any specific defence against these parasites. The mites live in small populations and show female-biased sex ratios consistent with local mate competition. Preliminary evidence suggests that the mites have haplodiploid sex determination which may explain how they are able to adapt their sex allocation to their population size.

Poblaciones meridionales de Lasius flavus (Fabr.) y L. myops Forel: estudio biométrico (Hymenoptera, Formicidae)

Abstract: espanolSe ha realizado un estudio biometrico (anchura cefalica, numero de ornatidios) en 469 obreras del par de especies Lasius flavus (Fabr ) y Lasius myops Forel Se demuestra que el criterio separador propuesto por Seifert (1983) para poblaciones septentrionales es perfectamente aplicable a poblaciones meridionales Las caracteristicas cromaticas de la cabeza en hembras y de la denticion mandibular en machos, sirven igualrnente para diferenciar ambas especies No parece haber variacion geografica en las variables utilizadas Hay un cierto grado de segregacion ecologica ya que L flavus nidifica a altitudes superiores EnglishCounts of ommatidia number versus maximum head width in 469 workers of the ant species Lasius flavus (Fabr ) and Lasius myops Forel provide evidence that the rule proposed by Seifert (1983) for central european populations is useful to differentiante meridional populations of both species The head colour pattern of females and mandibular dentition of males can also be used as identification tools There seems to be no geographical variation concerning these morphological characteristics L flavus nests at higher altitudes