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We know that in Tabanidae or another families that similar to it, males fed on pollens, but females fed from the blood! Why do they have different nutritional? Why and how their evolution has been separated? But still will find each other easily? Who can advise me??
Thank you very much!

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Females needs proteins, from blood, for their egg-production. Blood is a good source for it.

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I do not have the time to go into detail now, 21392, but I would like to mention the dance flies. The females of many dance flies need proteins and, thus, eat other insects, while the males just visit flowers. For many species the male catches a fly and gives it to the female before copulation. It is quite a common sight in Spring to see "trio's" in nature: male, female and prey.
Dance flies developed in the middle of the Mesozoic. In the same period the first real flowers developed. You can imagine easily that from pure carnivore dance flies flies developed, which began to frequent flowers for alternative food. The females, however, often needed, nevertheless, protein from prey for laying eggs.

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Is it the case that *both* males & females drink nectar for energy - but only females drink blood for the egg proteins? Both sexes have the same mouth-parts and so they are similarly evolved ... but the females just go for an additional food source.

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I'm so thanks from you,
but I want to understand that why do some evolutions separated between males and females, and they aren’t similar, while in another, for example Hypoboscidae both males and females are parasite and fed from animals and similar samples, not just carnivorous, maybe both being evolution on nectar or etc.?? Why don’t have a kind of evolutions?
even as ChrisR said, maybe some different between mouth-parts!
thank you very much

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Honestly I do not understand your question. Anyway, I think a question about evolution beginning with "why" will be often impossible to answer. For evolution as such there is no reason as there is for gravitation force not reason. Evolution happens, driven by natural selection, making use of the variation within each species as so beautifully written down by Charles Darwin.

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Okay, so thanks for your attention and your guide!

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Hi Sara - I think you are trying to make the question too complicated. Some species have extremely different morphology between males and females and others are very similar. If the genes that give different morphology/behaviour give that individual a better chance of breeding than others in the same niche then it has a greater chance of passing that trait on to its offspring... and so on. We don't wonder how a male Pheasant could have evolved to be such a different colour to the females ... and in the same way some flies have different behaviour that helps their genes continue.

Also remember that "species" is a human concept but in almost every species the individuals are not clones, they have slightly different genes that express slightly different traits ... but they all share a common ancestor that would look virtually indistinguishable from the current generation.

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I think, I knew you mean, now. definitely you're right, again thank you very much.

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Interesting Ruud, Ive not heard of Dance Flies before!