Complex sentence: It had been hypothesised that Lundy cabbage flea beetles and "Ceutorhynchus contractus" var. "pallipes" may help pollinate the Lundy cabbage, but observations of the taxa indicate that neither visit flowers.
Split into simpler sentences: It had been hypothesised that Lundy cabbage flea beetle and "Ceutorhynchus contractus" var. "pallipes" may have helped pollinate the Lundy cabbage. However, observations of the taxa indicate that neither visit flowers.