Male production in the ant Myrmica rubra L.

Smeeton, Linda (1980) Male production in the ant Myrmica rubra L. University of Southampton, Doctoral Thesis.

Abstract

The aims of this project were to determine the origin of Myrmica rubra males and to investigate factors influencing the production of worker reproductive eggs. In this species such eggs are always male. Lipid dyes were found which, when fed to adult ants, marked their eggs. These were then used in the field and laboratory to investigate worker egg production. The resulting data, along with those from sampling experiments, strongly suggest newly ecloding workers to be the primary, possibly sole, source of males. Egg sampling showed that male eggs were laid in late summer when there are many callow workers in the nests. Dissection of workers from field colonies showed that a higher 5 proportion of callow and pale-coloured have ova in their ovaries than older ants. The effect of the presence of older workers on egg production by callows is described.During field sampling information was gathered on colony development over two seasons and this is compared with the environmental conditions.Investigation of egg production by virgin queens revealed that they are unlikely to produce males due to their short lifespan and low fecundity.The pattern of egg production through a season for both female castes (queen and worker) is described. Colony site was found to affect the production of reproductive eggs by workers but colonysize did not. Calorific values of workers are shown to be positively correlated with their reproductive egg production and multiple regression including the effect of colony and individual worker size does not improve this. Calorific values are not correlated with mortality in workers, and show little variation within colonies. Larger workers produced more reproductive eggs than smaller workers and this was reflected in their ovary development. Older workers produced fewer reproductive eggs than younger overwintered workers,but in this case ovary development did not show a significant difference.The presence of small numbers of third instar larvae increased worker reproductive egg production whereas, past a maximum, larger numbers decreased it. A significant relationship between worker reproductive egg production and photoperiod was found with more eggs produced under long days. This was not affected by an initially opposite photoperiod. Physiological differences were caused by photoperiod in workers kept with or without queens. The effect of photoperiod on trophic egg production by workers and reproductive egg production by queens was changeable and insignificant.The findings of this project are compared with earlier work on the same and other species. Also their relevance to the ecology of the species is discussed.

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