Flowers printed for studies on pollinating insects

Sirris is scanning and printing flowers in polyamide for a researcher who wants to have models that can be reproduced and reused and are available in all seasons for pollination studies.

Aconites are flowers that are highly attractive to pollinating insects because, not only is their nectar very sweet but their late blooming provides end-of-season food resources, when these are becoming scarce. However, they are complex and the nectaries, the glands which secrete the nectar, are not easily accessible. Insects have to follow a particular path between the sepals of the hood to reach them and, in this way, they pollinate the flower. But not all of them are capable, especially because of their size or morphology. Some, like large bumblebees or bees, do not always take this path and use behaviour called "nectar theft", which consists either in slipping under the hood directly (for the smallest), or in piercing the flower hood with their mandibles to get to the food directly. In this case, they do not come into contact with the reproductive organs of the flower which is then not pollinated. 

A. L. Gauthier, a researcher at the UCL Earth and Life Institute, is working on this behaviour. Up to now the study equipment for complex flowers consisted of long tubes containing sugar water. This model was quite removed from the morphology of natural flowers. 

Sirris has been helping A. L. Gauthier to produce 3D models of the aconite flowers that are much more realistic. The extra advantage of this process is the possibility of continuing observations outside the blooming period and on identical flowers (thus eliminating a variability factor) which can be reused. 

Scanning the flowers is not easy, as the sepals are very fine, fragile and fade quickly. From the scan, Sirris constructed a 3D model with realistic thickness (0.5 mm) compared with the impression and printed it in 3 different resins by jetting and using a titanium alloy by laser fritting.

The researcher then tested the parts in terms of ease of cleaning, scent release, etc. Titanium appeared to be the most interesting but on the basis of a necessary compromise between cost, strength and resolution, polyamide fritting was selected.

Using these first prototypes, some small anatomical modifications were made. Inside the flower hood, by the nectaries, two protrusions were created perpendicular to the surface to allow the experimenter to attach a piece of cotton dipped in artificial nectar. The top of the hood was closed to force the insect, in order to reach the nectar, to choose either the normal path or theft, by on the one hand 1 mm holes pierced laterally and on the other hand the option for the insects of sliding the head under the hood (by the side). Finally, the stem was reinforced for easier handling. 

Using these printed flowers, A. L. Gauthier was able to study the insects' choice strategies according, for example, to the flower's colour or its scent, since each factor could be controlled separately.

Also Gauthier was able to carry out tests of nectar theft learning by the bumblebees and of the transmission of this strategy to the colony. 

This capacity of insects to learn is important for further study, for example in the event that climate change causes mutations in flowers that require behavioural adaptation of the pollinators.