letting nature back in

I have been foraging for distractions from anxiety while under lockdown. I have come across some oddities and marvels in our own backyard to share on naturebackin.

Bubble-blowing flies seem to me to be both odd and marvellous. Most but not all species of flies do this as well as other types of insects including some species of wasps and bees. Though it looks like bubble-blowing, the flies are rather engaging in the regurgitation of droplets of fluid. A droplet, which may be clear or opaque, appears at the end of the fly’s proboscis (tongue). If watched for long enough, very slowly the fly appears to suck in and then regurgitate the fluid several times in succession.

This fly, possibly one of the Tachinid flies, is stationary on a petal of a wild iris (Dietes grandiflora) while it bubbles a fluid droplet

So why do flies do this? It is not entirely certain why, but it has long been thought that it is most likely related to the digestive system and/or to do with thermoregulation.

The findings of several investigations into this bubbling behaviour in flies is summarised in the 2019 article referenced below. So for example, in addition to droplet regurgitation being thought to be a mechanism to evaporate excess water from liquid food or as a thermoregulatory mechanism, it has also been suggested that it might be a mechanism for getting rid of toxic substances. It might also be part of complex interactions between plants and insects. In fruit flies there is evidence that it might be to do with the production of sexual pheromones in males to attract potential mates.

After a while this fly stopped the bubble-blowing process and proceeded to spend some time apparently cleaning its forelegs and face before flying away

Tachinid flies are of medium size and are usually quite bristly. The adults feed on nectar and play a significant role as pollinators. They lay their eggs on or near a variety of host species of insects and centipedes where the larvae become internal parasites feeding on their hosts from within. Because their hosts include caterpillars, beetles, grasshoppers and other insects that can be pests to many agricultural crops, Tachinid flies are important as biological pest controllers for agriculture (as well as for gardens).

Another fly that is bubble-blowing in the garden. The droplet that this one is regurgitating is opaque and ruby-red in colour

At first I thought that this fly was likely to be another Tachinid, but because of its red eyes and striped thorax, I think that it is one of the flesh flies in the Sarcophagidae family. These flies feed on decaying organic matter, including animal corpses, as well as on faeces, where the female flies deposit live larvae (maggots). The maggots’ superfast eating habits contribute to getting rid of rotting matter, and like other fly and beetle species that utilise carrion, they are beneficial members of nature’s clean-up crews.

A subfamily of Sarcophagidae, the Mitogramminae, are specialist parasitoids of wasps and bees, and in addition there is one species, the locust fly (Wohlfahrtia pachytyli) that parasitizes brown locusts (Locustana pardalina) and is an important biological control agent for locust swarms.

Having sucked the droplet back in, the fly is starting to regurgitate another droplet that swells in size until once again it sucks it back in before repeating the process several times

I have mentioned bubble-blowing in a previous post where I also discuss the importance of flies as pollinators. Although usually despised and swotted on sight when possible, flies have overtly beneficial aspects that are not well known or are overlooked. These beneficial aspects include their roles as pollinators, pest controllers and their disposal of carrion and other rotting material. In addition to all that, their bubble-blowing is an intriguing oddity to marvel at.

This video clip shows the same fly photographed above sucking in and regurgitating a droplet of fluid.  

Please excuse the hand-held camera wobbles.  Unexpected sightings such as these have to be captured immediately without delay and often the critters can only be observed from awkward angles so using a tripod is not something I manage to do.

Tomorrow we enter another level of lockdown, where some additional areas of economic activity will be allowed in an incremental fashion. Because we are in the relatively early stages of the pandemic in this country, the conditions of the lockdown remain severe, with the addition of a nationwide curfew from 8 p.m. to 5 p.m. for everyone except essential workers.

Apart from those permitted to leave home to go to work, the rest of us may only leave home to buy food or medicine, to seek medical care or to access social grants. However, from tomorrow we may leave home to exercise, that is to walk, jog or cycle, but only between the hours of 6 a.m. and 9 a.m. Also when exercising, we are limited to remaining in our own neighbourhood within a maximum radius of 5 km.

So tomorrow morning, after five weeks of lockdown, we will be venturing out to take ourselves (and our dogs) for a much needed walk. When going out, in addition to sanitizing and maintaining social distance, it is mandatory that everyone masks the nose and mouth by using a homemade fabric mask or a scarf or even a T-shirt.

For anyone interested in making their own face mask, I used this free pattern to make a mask that fits really well – see https://www.craftpassion.com/face-mask-sewing-pattern/#face-mask-pattern

Stay safe everyone!

References:

Guillén, L., Pascacio-Villafán, C., Stoffolano, J. G., López-Sánchez, L., Velázquez, O., Rosas-Saito, G., Altúzar-Molina, A., Ramírez, M., & Aluja, M. 2019. Structural Differences in the Digestive Tract between Females and Males Could Modulate Regurgitation Behavior in Anastrepha ludens (Diptera: Tephritidae). Journal of Insect Science 19(4), 7. https://doi.org/10.1093/jisesa/iez070; Londt, Jason. 2009. Suburban Wildlife in KZN. A Wildlife Handbook, WESSA KZN; Picker, Mike, Griffiths, Charles & Weaving, Alan. 2019. Field Guide to Insects of South Africa. Cape Town: Struik Nature.

Posted by Carol