Dioctria's picture

Not the shieldbug!

Observed: 12th August 2011 By: DioctriaDioctria’s reputation in InvertebratesDioctria’s reputation in InvertebratesDioctria’s reputation in InvertebratesDioctria’s reputation in InvertebratesDioctria’s reputation in Invertebrates

I'm interested in the white blobs attached to the pronotum of this Parent Shieldbug (Elasmucha grisea). I believe they are Tachinid eggs in the subfamily Phasiinae. Can the ID be taken any further based on the particular host species, egg location or some other point?

Species interactions

No interactions present.


Dioctria's picture

More Questions

The egg on the left appears deflated, does this mean it has hatched?

Does the larva burrow directly through the pronotum, which would be rather impressive, or does it hatch and then seek out a weak point to enter the host?


Wildlife Ranger's picture

Tachnid Parasitic life Cycle

I am not sure of the the specific Life cycle of some of the Genus Like Phasia which are commonly seen on the GSB but here is agood link to a PDF describing a typical stratgey of a Tachnid in a Beetle they are also common to Caterpillars beetles etc where the entry point is through the digestive system although most bar 3 or so British SB are phytopahagous - eat plant material


In all honesty i think it woould be a tall order to ID a Tachniod species from an egg !!

There is suprising little known about this aspect of Shieldbugs but the Tachnid Recording Scheme holds some interesting info



Best Wishes


Dioctria's picture

Thanks for those links Colin,

Thanks for those links Colin, I must admit, I don't recall visiting the Tachinid Scheme site before. (Apologies to Matt!)


Matt Smith's picture


There are a number of Tachinid species that attack Shieldbugs but there are only a limited number of host specific species.

If I had to hazard a guess I would say that the most probable Tachinid in this instance species is Subclytia rotundiventris. This lays external eggs on the host, on hatching they bore directly into the host and Subclytia has been reared from this host on a number of occasions. It won't be a Phasia species because those insert the eggs into the host abdomen. However, the only way to be sure is to rear out the Tachinid.

Did you keep the Shieldbug?

Tachinid Recording Scheme


TRS Facebook Page

Dioctria's picture

Thanks Matt, I had seen that

Thanks Matt, I had seen that species mentioned a couple of times on similar photos on Flickr.

I'm afraid I didn't keep the bug as I didn't recognise what the eggs were at the time. If I come across any in future I will certainly do so however and photograph what emerges. I presume a Parent Bug would be fairly easy to keep on a regular supply of Birch?

So that leaves me at Phasiinae but not Phasia. Thanks for taking it as far as it will go.

(Skimming through my other images of Parent Bugs I found one other with an egg in a similar location so it's obviously not uncommon to find them.)


Wildlife Ranger's picture

SB parasitism

Keep us informed of your Obs David . Tachnids in this form are not uncommon but often go unnoticed ,

Best Wishes