Chlorpyrifos has been off the market to non-professional consumers for some years now.  And that is probably a very good thing, given that many don't follow package instructions.

A few years ago I had a student who wanted to study the effects of chlorpyrifos on embryonic development.
She found:

1.  Embryos exposed to chlorpyrifos were significantly underweight compared to controls. 
2.  Embryos exposed to chlorpyrifos had higher incidences of birth defects than controls.

Over the years I have supervised a number of student projects looking at embryonic toxicity.  We saw the above two outcomes over and over (and more specific problems I won't go into here).

In general, any physiological response to a stressor requires energy.  In the case of embryos, if they have to exert metabolic energy to deal with 
stress, it comes at the expense of growth.  An example:  infants born to smokers.  They are underweight, on average, compared to infants born to non-smokers.  In the case of adults, consider cancer patients.  They lose weight....this is because their bodies are under tremendous stress and it costs energy to deal with stress.  Same thing happens to stressed bees.  They need more energy.

Incidentally, there is now evidence showing that maternal effects influence epigenetic development of the baby in a "sins of the father (and mother)" sort of way, and that somewhat alarming....because I know what that could potentially indicate.  Even for bees.

Christina






     
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