>It’s a work around as they are not vertebrates. However they lack any form of adaptive immunity (T cells and B cells) so they will only provide insight into innate immunity that will only be partially relevant to human disease.

Yes, that is true! The lack of adaptive immunity is an important limitation of this model. But it turned out that the innate part of immunity is of comparable, if not more significance, for human health than adaptive immunity. So it is a great chance to study the innate part of immunity exclusively. But of course, if you want to study T-cells and B-cells, you can not use insects like Manduca. Thank you for this very constructive and knowledgeable comment!