I dont know a lot about this, but this is an intersting topic.
And I think its not weird at all there are factors influencing the male/female ratio. Take for example turtles: the male/female ratio in influenced by a small thing as temperature...
An other examples: there are bacteria out there "killing" male insects... and influencing the male/female ratio so that there are almost no males left... (as you allready mentioned)
Or what about the fact that some pesticides/herbicides also influence the male/female ratio.. (there are some pesticides out there killing males.. and not females for example)
And many other examples...
So I can imagine there is a influence of the diet.
(or maybe because a factor giving with the diet: example a chemical that is in/on the food for example...?)
Or maybe its just because of the male killing bacteria that the beetles start producing more males.
, I can imagine that the beetles adapt and start making more males, we dont know how she did the experiment? Maybe she had infections or started with beetles that were allready adapted to the male killing? Did she use the same beetles for the different diets for example? or did she use different beetles for each diet? This can influence the results I think... and the diet itself: maybe the "best" diet is a diet that causes stress/malnutrition or something else that shifts the ratio?)
And to end my post, you might want to check the following papers:
Hodek I, Ceryngier P. 2000. Sexual activity in Coccinellidae (Coleoptera): A review. European Journal of
Osawa N. 2001. The effect of hibernation on the seasonal variations in adult body size and sex ratio of the
polymorphic ladybird beetle Harmonia axyridis : the role of thermal melanism. Acta Societatis Zoologicae
Osawa N. 2002. Sex-dependent effects of sibling cannibalism on life history traits of the ladybird beetle
Harmonia axyridis (Coleoptera: Coccinellidae). Biological Journal of the Linnean Society 76:349/360.
Gotoh T, Niijima K. 1986. Characteristic agent(s) of abnormal sex ratio (SR) in two aphidophagous
coccinellid species. In: Hodek I, editor. Ecology of Aphidophaga. Prague & Dordrecht: Academia & Dr
W. Junk. pp 545/550.
Gotoh T. 1982. Experimental transfer of abnormal sex ratio in the lady-bird beetle, Harmonia axyridis
(Pallas) (Coleoptera: Coccinellidae). Applied Entomology and Zoology 17:319/324.
George E. Heimpel and Jonathan G. Lundgren 2000, Sex Ratios of Commercially Reared Biological Control Agents. Biological Control Volume 19, Issue 1, September 2000, Pages 77-93
Or maybe even this one (links food with the act of sex): Mating refusal and its significance in females of the ladybird beetle, Harmonia axyridis by SHOHKO OBATA , Physiological Entomology
Volume 13, Issue 2, pages 193–199, June 1988)
Edited by pito, 29 April 2011 - 01:43 AM.