"Clearly, there are plenty of sublethal effects due to exposure to neonics, even at
 field-realistic concentrations."

Toxicology is a curious science.  Very often you can not quantify low level effects.  So the usual way to treat the data is to assume the response is linear.  Clearly a linear response is not always right.  Maybe never right.  A couple of examples of non linear responses are trace nutrients and the ladder death rate.

Many nutrients are essential to life.  For example some vitamins and some minerals must be eaten.  In both cases too little and the organism dies and too much it also dies.  But, the right amount offers optimum health.  A friend of mine who is an MD had for one of his first patients, when he was handed a hospital ward as a student, a pharmacist who took every iron supplement his drug store sold.  My friend lost that patient to iron poisoning.  Clearly these are non linear dose responses.

Suppose I wanted to test the LD50 for dropping a rat off a ladder onto concrete.  I go higher and higher up a ladder and drop the rat.  Perhaps at 30 feet I find half the rats die from the impact.  A linear response would predict that at 15 feet 25% would die.  At 7.5 feet 12.5% would die.  At 3.75 feet 6.25% would die.  Etc.  Does anyone really think a fall of 3.75 feet would kill one rat in 1000 much less six per 100?

Generally when you test chemicals in feeding tests you see some effect at some feeding level.  Take that same total dose and divide it over several days and you typically see much less effect.  Take that total dose and feed it divided equally over 30 days and chances are you see nothing.  All organisms live in a fairly toxic world.  Mom nature has been in the business of making toxins forever.  Plants make things like terpines and nicotine to protect themselves from predators such as insects and grazing animals.  Some legumes make enough cyanide to be toxic to grazing animals.  Even lethal early in the morning when dew is still on the plants.  Lots of plants make toxic levels of oxalic acid.  So, all organisms have had to either evolve degradation pathways to deal with these toxins, avoid eating some plants or eat only small amounts of the plant.  At too high a concentration those things will  kill.  This is true for humans and it is true for insects.

Would the world of bee keeping be easier if there were no pesticides used for Ag or home lawns or golf courses or railroad rights of ways?  In some ways clearly yes.  There sure would be a lot more forage generally available.  Guys like Charles who live in corn and soy bean deserts would have lots more for their bees to work.  I do not doubt for a minute that bees are harmed by direct toxic affects in some cases by pesticides.  But, if we got rid of all pesticides we get rid of oxalic acid and formic acid and other chemicals we use to treat varroa also.  So, as I see it we need to strike a balance that allows the corn and bean farmers to make their living while we also manage to keep our bees alive.  This is always going to be a tough balancing act with the bee keeper pushing in one direction and the corn and bean guys, the golf course guys, the rail road guys and even cities doing sprays for mosquitoes pushing the other.  I do not expect any perfect
 solutions for everyone all the time.  About the best outcome is no one hurts the other guy so much he can not survive.  All in all it seems to me that neonics used properly give us that standoff.  There is no question that improper neonic use can kill whole hives.  But, that sure does not seem to be the normal case based on field data.  Too many bee keepers are doing ok in corn, soybean and canola deserts to seriously argue that neonics are a disaster to bee keeping.  I think herbicides probably hurt us more as they remove so much forage for our bees.

Dick
" Any discovery made by the human mind can be explained in its essentials to the curious learner."  Professor Benjamin Schumacher talking about teaching quantum mechanics to non scientists.   "For every complex problem there is a solution which is simple, neat and wrong."  H. L. Mencken

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