Referee 2's review (John Obrycki):

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N.B. These are the comments made by the referee when reviewing an earlier version of this paper. Prior to publication, the manuscript has been revised in light of these comments and to address other editorial requirements.
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This an interesting study. I have several minor comments that the authors may wish to consider.
(1) In the abstract and text, authors state "no general effects on parasitoids existed". This statement needs clarification. Is this due to relatively few studies of parasitoids or due to lack of effects of Bt transgenic crops on parasitoids. The authors note the effects on Macrocentris, a parasitoid of the European corn borer. Would one expect generally negative effects on parasitoids that attack hosts targeted by the Bt toxins ? The analysis may not show this, but the statement about no general effects on parasitoids may be mis-interpreted.
(2) In the abstract the authors state that predators and herbivores increased in Bt crops -- does this mean that studies were conducted over several years and levels of these species increased over time or that levels were higher in a given year when compared to sprayed non-Bt controls.
(3) In Abstract, would significant declines in a parasitoid that attacks immature stages of a lepidopteran species that is targeted by the Bt crop be considered a systematic effect ? The authors discuss Macrocentris and the European corn borer in the text, but do not consider this to be a systematic effect.
(4) Introduction -- first paragraph -- authors state "... studies have focused almost exclusively on taxonomic level", this is not a fair representation of the literature cited by the authors (e.g., Schuler et al 1999, Lovei and Arpaia 2005, Romeis et al 2006)
(5) Methods start on page 5 and continue to page 13, I suggest the length of this section be reduced. Some of the details can be moved to supplemental information sections.
(6) The authors might provide more information about the data set (years included) and include mention of more recent publications in this area (e.g., Torres and Ruberson 2007 Annals of Applied Biology 150:27; Torres and Ruberson 2006 Biological Control 39:47)
(7) Page 16 line 3 -- not clear "no significant effects sizes"
(8)Suggest that the authors consider reducing the length of the results and discussion sections. Focus results on data presented in tables and graphs.
(9) References 41 and 42 -- Is this the USDA?