A few coleopteran trivia concerning Cetonia aurata, or more precisely its foraging behaviour on Viburnum opulus in Sweden:
R. Englund (1993). Movement patterns of Cetonia beetles (Scarabaeidae) among flowering Viburnum opulus (Caprifoliaceae). Option for long-distance pollen dispersal in a temperate shrub. Oecologia 94:295-302.
This paper is also interesting per se, because as you may have noticed, it has a subtitle. This is something I’ve not seen in recent papers, it seems that this way of announcing disappeared within the last decade (let’s play the game of finding other biological papers with subtitles!).
As I said, I’m just throwing up trivia (hey trivia can be of interest!), and what it would mean for plants to be visited by this wonderful beetle. The paper is of course taking on other things. Also, it was dealing with marking individuals and the study lasted four years. The authors don’t document observing beetles marked from the previous years so that we can infer that late emerging individual probably don’t make it through spring since even ‘regular’ specimens don’t seem to survive wintertime (or to say at the safest: they probably don’t in Northern Europe… These are the most frustrating facts, the ‘negatives’). At least that’s giving some infos with regard to my wondering about fall emerging adults… But let’s go on foraging and pollen fests:
– Cetonids abundance vary from one year to the other, seemingly with a two-year cycle (that’s well known, but there we have a regular documentation of the fact). They are most active between 1 and 2 p.m. (hum, they can also be met at dusk in summer, or anytime around rotting fruits but that’s another story). Lazzy beetles (or because of lucky shrubs with a lot of nectar) stayed up to six hours foraging on the same plant (on the other hand, the cetonids in upmost hurry just landed for a few seconds).
– Short flights (4-10 m.) were preferred, but one every five is a long distance move (>75 m.), which allows for quite long distance dispersal of pollen for the plant (compared to locally active pollinators just seeking for the next plant, which may also be your next of kin).
More precisely, while the average neighbour distance was 6 m. at the study site, the average flight of chaffers between successive plants was 18 m. Therefore chaffers are really dispersing pollen (moreover, they are hairy beasts below, retaining a lot of pollen grains, but they never seem to groom themselves, contrary to bees). Unfortunately, they forage a lot on a single plant and may well be involved in a lot of geitonogamous pollen tranfers, that is, promoting self fertilization…(Indeed, they simply walk from a flower ot the other).
– The most important characteristic for plants to get visits from Cetonia beetles is the presence of flowers (and of course inflorescences too, though the plant height and volume apparently play an important role attracting these beetles). Neighbours did not significantly influence focal plant visits, there is therefore no attractive effect from direct neighbourhood (which is consistent with the observed flight patterns). This is somewhat different than common bee behaviours, where surrounding plants benefit from the intense local foraging activity, if visits are not too numerous.
But interestingly, chaffers are demonstrably constant in the species they feed on. Switches on different species tend to occur only when the preferred species is ending its flowering season and is not worth its prime rewarding status anymore. There is thus sort of a sequential diet through time. Translated in a plant point of view, this is interesting because with such pollinators, plants don’t need anything special to have them actively selecting for the very same species. This is cheap evolution compared to plants that adapted to specificity in pollinators.
Hum, but these are self-serving pollinators that are eating their load of pollen. Maybe not that safe!