The crenellate lining of the Dufour gland in the genus Aenictus: a new character for interpreting the phylogeny of Old World army ants (Hymenoptera, Formicidae, Dorylinae)

The Dufour gland epithelium in Aenictus has a crenellate appearance, a condition previously found only in the primarily African genus Dorylus . This character, taken alone, strongly suggests that these two genera share a common ancestry, as is presently reflected in their placement in the subfamily Dorylinae, and that an independent, convergent origin for them, as has been proposed in the triphyletic hypothesis for army ant evolution, is incorrect.     

Cyathotheca suecica and its bearing on the evolution of the Edrioasteroidea

The European Ordovician edrioasteroid Cyathotheca has a variable tubular theca composed of a single plate. The oral surface is covered by five large inter-radial deltoids fused to biserial ambulaeral cover plates, and a periproct in the C-D inter-radius accompanied by two or three adanal plates. Cyathotheca lacks ambulaeral flooring plates. The American and Baltic Ordovician genus Cyathocystis is identical except that it has a complete ring of small peripheral plates surrounding the deltoids. Both genera are assigned to the family Cyathocystidae. The Devonian genera Timeischytes and Hadrochthus are regarded as neotenous offshoots from the Agelacrinitidae and unrelated to cyathocystids. True cyathocystids arose neotenously from the Cambrian stromatocystitids by attachment of the centro-dorsal and failure to develop further aboral or ambulaeral plates. This branch represents a separate evolutionary line to the main stromatocystitid-edrioasterid-isorophid line.     

Evidence for an Ethylene Requirement to Reduce Soaking Injury in Bean Seeds and the Beneficial Effect of Heavy Metals

In addition to CO₂, low concentrations, in decreasing orderof effectiveness, of Ag, Ni, Hg, Zn, Co, Pb, and Cu salts tendedto reduce soaking injury in bean seeds. Their effects did notappear to be due to ethylene antagonism. The CO₂ effect wasnot related to it lowering the pH of the soaking solution. Soakinginjury was aggravated by L-a-(2-aminoethoxyvinyl) glycinehydrochloride(AVG) and 2,5-norbornadiene (NBD) and this effect was reversedby ethrel. Soaking in the presence of an ethylene absorbantHg(CIO₄)2 increased injury. The beneficial effect of CO₂ wasdiminished by NBD and this was reversed by ethrel. Ethrel andethylene tended to decrease soaking injury. Injurious treatmentsresulted in less ethylene release by soaked seeds than beneficialtreatments. It is concluded that ethylene does not cause soakinginjury but appears to be partially required for its prevention. Key words: Phaseolus vulgaris, soaking injury, ethylene, ethylene antagonists, heavy metals     

On the similarity of the Dufour gland secretion and the cuticular hydrocarbons of some bumblebees

Abstract. There is a close correspondence in composition between the hydrocarbons of the Dufour gland and the cuticular hydrocarbons of workers of some bumblebee species. This correspondence is characteristic of the species, and independent of the place and time of collection.     

On the maintenance and origin of alternative strategies in the Ruff Philomachus pugnax

This paper has tried to answer the question of how the independent and the satellite strategy of the Ruff originated and has been maintained during evolution. It is not intended as a report of a piece of completed research but gives a number of tentative, but testable hypotheses. Data are presented that independent males and satellites are equally successful in copulating, provided that almost all copulations occur on leks, and independent males and satellites spend an equal proportion of their time on leks. The extent that males with the different strategies are attached to leks is analysed. Within the group of independent males, considerable differences exist: a resident male is strongly attached to only one particular lek and a marginal male seems to sample many leks. A satellite male behaves intermediately: he is attached to a limited number of leks. The mechanism for the maintenance of both strategies could not be explained by competition for resources (copulations). Contests between independent males and satellites are asymmetric, the satellite being the weaker contestant. The mechanism seems to be due to enlarging the accessibility of the resource by cooperation between both strategies. The ideas on the origin of the system are based mainly on the behaviour of females. There is no relation between the distribution of leks and the size of a female's foraging area, except that most leks are situated along the migration route. It further seems that the number of copulating females in the Netherlands is larger than the number of males on leks, but the number of breeding females is much lower. It is suggested that many females copulate on migration, which is related to extreme breeding conditions in the north of the range. Apart from a change in the sex ratio from south to north, a change in the proportion of satellites is also predicted. The origin of the system is ascribed to the incompatibility between favourable food conditions for chicks and further possibilities for inter-male competition on leks in the same area. The satellite strategy is considered as being derived from a non-competitive strategy accompanying females on migration. In the phase of cooperation between resident and satellite males, individual recognition became important. This could be the factor underlying the evolution of white plumages in satellites and the extreme plumage diversity in independent males.     

Host‐plant genotype mediates supply and demand of animal food in an omnivorous insect

1. Omnivorous predators can protect plants from herbivores, but may also consume plant material themselves. Omnivores and their purely herbivorous prey have previously been thought to respond similarly to host‐plant quality. However, different responses of omnivores and herbivores to their shared host plants may influence the fitness, trophic identity, and population dynamics of the omnivores. 2. The aim of the present study was to show that an omnivorous heteropteran (Anthocoris nemorum L.) and two strictly herbivorous prey species respond differently to different genotypes of their shared host plant, Salix. Some plant genotypes were sub‐optimal for the omnivore, although suitable for the herbivores, and vice versa. 3. The contrasting patterns of plant suitability for the omnivore and the herbivores highlight an interaction between plant genotype and omnivores' access to animal food. Plant genotypes that were sub‐optimal for the omnivore when herbivores were experimentally excluded became the best host plants when herbivores were present, as in the latter situation additional prey became available. By contrast, the quality of plant genotypes that were intrinsically suitable for omnivores, did not improve when herbivores were present as these plant genotypes were intrinsically sub‐optimal for herbivores, thus providing omnivores with almost no additional animal food. 4. The differential responses of omnivores and their prey to the same host‐plant genotypes should allow omnivores to colonise sub‐optimal host plants in their capacity as predators, and to colonise more suitable host plants in their capacity as herbivores. It may thus be difficult for Salix to escape herbivory entirely, as it will rarely be unsuitable for both omnivores and pure herbivores at the same time.