It's a Small-headed Fly from South Africa! - Observation of the Week, 4/26/20

Our Observation of the Week is Psilodera fasciata small-headed fly, seen in South Africa by @cecileroux!

Cecile wrote a wonderful little piece for this week, so I’ve decided to publish it here in full. I’ve added some links to her text and appended a paragraph about this remarkable family of flies. Enjoy! - Tony

I was lucky to be born into a family that loves nature. I have always loved being immersed in nature, watching, listening, appreciating. My mother studied Entomology, but I only started following in her footsteps when my husband gifted me a camera with a macro lens. I was immediately hooked! 

Shortly after getting the camera, I was introduced to iNat by a botanist friend, @steve_cousins, who has since sadly passed away. He was doing his doctorate on our critically endangered Renosterveld, and while he studied the vegetation, I followed and started to record the infinite variety of insects and spiders in some of the few remaining veld remnants in the Swartland. We talked about pollination, and the importance of bees, and as I watched the flowers, I was amazed to see the variety of pollinators. I realised that not all that buzzes are bees, and started to look closely, and that is how I first came to know the small-headed fly, Psilodera fasciata. Along with the Bombyliidae family, they are some of my favourite flies, and I am grateful that they seem to like my rather unkempt indigenous garden, where I found this one. One needs patience to photograph these flies, they take ages to decide where to settle down. But the patience and sore knees and dirty elbows are always worth it!  Lockdown is made better by the company of all the insects and spiders in my garden.

Currently some friends and I are endeavouring to record the abundance of life on Kasteelberg, the mountain guarding over our village. The renosterveld and fynbos vegetation, the birds, small mammals, reptiles and invertebrates. I am at my happiest when I am out in the veld, discovering and observing. My main interest is spiders, but I am captivated by every small thing that moves! The best part of observing the small life around me, is being amazed and excited almost every day, a wonderful privilege in a jaded world. So much to discover still! Apart from my own pleasure, I also hope to teach people through my photos that insects are not pests, and spiders are not to be feared.

I am not a scientist, and field guides, although invaluable, can go only so far. I find iNaturalist a wonderful site where like-minded and knowledgeable people from all over the world become teachers. I am learning so much, and appreciate every ID and discussion.

Psilodera fasciata is a member of the Acroceridae family, known commonly as small-headed flies or spider flies, which contains about 500 species around the world. While the inspiration for “small-headed” is obvious from Cecile’s photo, “spider flies” refers to this family’s predilection for parasitizing our eight-legged friends. Female Acrocerids lay hundreds or even thousands of eggs. Hatchling larvae seek out spiders and make their way to the host’s insides, consuming it from within then pupating outside of the host’s depleted body. Adults feed on nectar and often possess enormous proboscises, as Cecile photographed here. When not in use, the fly tucks this proboscis under its body, and you can sometimes see it protruding past its rear end.

- Speaking of egg laying, check out an Acrocerid doing just that - in slow motion!

- Here’s one with an insanely long proboscis, photographed by bernardo_segura.

Posted on April 27, 2020 04:56 AM by tiwane