Mydas fly (Phyllomydas sp. likely quercus)

The Mydas Touch (Part Deux)

Had a visit to the Oakleaf Fleabane by the mydas fly pictured up top so I thought I’d dust off my lost article on the different species in this family that are documented thusfar at my place.

Dateline:  September 29, 2014

A quick look might have you thinking Mydids are robberflies.

This week I got an email from Bugguide giving confirmation of a fly species that graced my place a year ago.  I had pretty much forgotten about the submission, but the confirmation had a timely arrival since I was stumped earlier in the week on what I might write about today.

Oddly, these insects are similar to the Robber Flies (Asilidae) I wrote about in the past. As I reported then, robberflies mimic bees.  This family of flies are also mimics, but they pretend to be wasps and include the largest flies in the order Diptera. They are Mydas flies (Mydidae) and I’ve several different genuses come visit over the years.

After a year I got confirmation on the species of this fly: Mydas maculiventris
M. maculiventris does resemble a wasp.

“Members of this family are commonly referred to as mydids.”  Mydids, like the robberflies are a hefty bunch size-wise and although small in numbers, they are VERY obvious when they are flying around or alit on foliage. They can be distinguished by the elongated clubs on their antenna, which stick straight out from their heads. It sort of resembles a “Y”.

Mydids don’t seem to show a heck of a lot of beneficial qualities as adults.  There really isn’t much written about the habits in this stage of life. They don’t appear to be a predator of anything, either pest or beneficial since they lack mandibles. They also aren’t commonly seen and there are indications that they have a short life span.

Phyllomydas parvulus. I guess I’ll be having more of these around soon. This is the second species in this genus that I’ve encountered.

There is some anecdotal information that adults are visitors to Saw Palmetto (Serenoa repens) flowers so that would indicate some potential pollination duties.  Since I have lots of saw palmetto around, it could be why I have seen a lot of these rather large, beefy flies.

The P. parvulus pair could have cared less about me and the camera.

Since the 19th century it was believed that adult mydas flies live predatory on other insects in a manner similar to the related Asilidae. However, investigations showed that a fair number of adult males feed on flowers while females seem to rely only on the fatty substances accumulated in their abdomen. Species with vestigial mouthparts do not feed at all.

Their larvae is a whole other story.  Most larvae of some species of Mydas flies are predators that can be found in rotting wood munching away on beetle larvae. Mydids undergo complete metamorphosis.

The larvae of M. maculiventris feeds on GRUBS!

There is one species in particular that may have significant benefits since its larvae are soil inhabiting and prey on plant eating white grubworms and other larvae of beetles.  That one is M. maculiventris, who appears to mimic Paper wasps (Polistes spp.).

Mydas Fly (Mydas clavatus)
Mydas Fly (Mydas clavatus) Jet black with orange markings so I have documented two species in this genus.

The other species that I have found visiting in adult stage are M. clavata, Phyllomydas parvulus and P. quercus.

Phyllomydas quercus resting on a bald cypress tree seems to maybe mimic a spider wasp.

So, keep your eyes open and welcome this family of insects that secretly does good work in your beautiful wildlife garden.

* This tale was originally published by Loret T. Setters on September 29, 2014 at the defunct national blog beautifulwildlifegarden[dot]com. Click the date to view reader comments.



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