Does the jury need to instruct the jury on multiple conspiracies?

The government argues that here the jury instructions were sufficient to permit the jury to consider the defendant's theory of defense. The defendant's theory of the evidence was that he had had drug dealings with one member of the conspiracy, but was not part of the conspiracy charged in the indictment. In this case, however, there is no evidence of separate conspiracies. Cf. United States v. Zemek, 634 F.2d 1159, 1168-69 (9th Cir.1980) (where evidence tends to show a single conspiracy, failure to instruct jury on multiple conspiracies is not reversible error). If the jury believed the evidence presented by the government as to the existence of any conspiracy, it was the conspiracy charged in the indictment. There was therefore no basis in the evidence for the defendant's multiple conspiracy claim. He was given ample opportunity to argue his theory of the case to the jury, and the instructions advised the jury that it could convict only if it found that the defendant was part of the conspiracy charged. No further instruction was required.