The full question here involved insect-flower interactions: insects pollinate, but do they do anything else to help flowers, such as help disperse their seeds. Surprisingly enough, besides exceptional cases, no!
Animal-aided seed dispersal in plants is carried out mostly by vertebrates, who eat the fruit or the seed then defecate the seeds at another location. When it comes to insects, only the ants have been found to play significant roles in seed dispersal, in an interaction called myrmecochory. The few plants that use ants as seed dispersers produce seeds with an elaiosome – a tasty covering that ants love. The ants carry this seed back to the nest where they feed on the elaiosome, leaving the seed itself unharmed, and the seed lies dormant until conditions are ideal enough for germination.
But besides the ~32 genera of ants (Beattie, 1985; number probably outdated by now) that have this interaction, other insects show unique associations – a couple of bee species, several beetles, etc. – but definitely no general trend. I’m not sure why this is so: after all, the insect-flower coevolution is one of the greatest events in evolution </bias> and the single largest driver of biodiversity for the past 100 million years. If I had to venture a guess, I’d say it’s because seeds are generally big, so the job is better done by vertebrates… but many beetles are more than capable of carrying seeds. I have no literature that deals specifically with the issue though (undoubtebly some does exist, but I have never had to deal with the subject in much detail).
Beattie AJ. 1985. The evolutionary ecology of ant-plant mutualisms.