obturaculum
From ZooTerms (Dictionary of Invertebrate Zoology)
Arthropoda: Insecta) In Anoplura, a connective-like tissue structure that divides the hemocoel of the head from the thoracic hemocoel; continuous posteriorly with a heavy coat surrounding the thoracic ganglia; neck-plug.
obturaculum (noun; Latin diminutive obturare, to plug or close): (