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Photo#934493
Another Grotea from Sweeney Ridge - Grotea californica - female

Another Grotea from Sweeney Ridge - Grotea californica - Female
Sweeney Ridge, San Mateo County, California, USA
June 22, 2013
I find it amazing how certain ichneumonid groups can detect where larval host chambers are located within plant stems or wood. As I understand it (or mis-understand?), they palpate the surface with their antennae (or "antennate") and somehow feel (or "tactilely hear") a characteristic response (e.g. hollowness or change of density, or maybe vague movements of larvae within?). I believe it's thought to be a mostly tactile process...but perhaps they can also sense chemical cues emanating from the larvae, or the plant tissues response thereto.

Of course, it's also amazing that, once found, they can drill into the stems or wood, and then deposit an egg through that very narrow ovipositor...right onto a host larva!! Below is an image of a female G. californica ovipositing, taken on the other side of the San Francisco Bay from the images here:



The anatomical mechanics of how ichneumonids achieve this are fascinating. Check out the image below of (the much larger) species Megaryhssa macrurus:



An abstract for a very detailed article on surprising anatomical morphology and mechanics involved in oviposition for Megaryhssa macrurus can be read here.

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Another Grotea from Sweeney Ridge - Grotea californica - female Another Grotea from Sweeney Ridge - Grotea californica - female Another Grotea from Sweeney Ridge - Grotea californica - female Another Grotea from Sweeney Ridge - Grotea californica - female Another Grotea from Sweeney Ridge - Grotea californica - female