2-channel instrumentation amplifier (AD623) test circuit that provides in-situ pre-amplification of bipolar recordings from two muscles. The circuit is powered by two 2 1.55V Energizer 337 batteries and weighs 0.38g. It can be lifted easily by the moth. Data output is through fine trailing wires. (A) Top and (B) side view of the circuit assembled on the shaft of a hypodermic needle. Two pairs of 0.001" diameter insulated stainless steel electrode wires are threaded through the bore of the needle and emerge at the anchor plate, near where they will be implanted in the moth. (C) Front view of the an adult Manduca carrying the circuit. The anchor plate is glued onto the moth between the bases of the hind- and mid-legs. (D) Close-up lateral view of the circuit on the moth. Two pairs of electrode wires are inserted directly through the exoskeleton into two units of the subalar muscles for bipolar, extracellular recording. (E) Sample data from a flight sequence (upper trace). lower trace: expanded view.