Below is a recent article discussing insectivory among orangutans. Note that
insects are a staple in the diet rather than a fallback food. Interesting! That
chimps use tools to collect insects is common  knowledge. Now it appears that
orangutans engage in insectivory where the tool-making skills are present. More
evidence against the "orangutans are natural vegetarians" claims.

Journal title:    American Journal of Physical Anthropology
Citation details: Volume 125, Issue 2, pp. 162-174

Article title:    Intra-and interpopulational differences in orangutan (Pongo
pygmaeus) activity and diet: Implications for the invention of tool use
Article authors:  ElizaBeth A. Fox, Carel P. van Schaik, Arnold Sitompul,
Donielle N. Wright

http://www3.interscience.wiley.com/cgi-bin/abstract/107061099/ABSTRACT

Abstract
Tool manufacture and use have been described for wild orangutans (Pongo
pygmaeus), with appreciable interpopulational differences in tool complexes.
The ecological factors that contribute to these differences require
investigation. Significant interpopulational differences in diet suggest that
ecological factors contribute to variation in tool-based insect foraging. Using
4 years of behavioral data from the Suaq Balimbing Research Station (Sumatra,
Indonesia), we tested predictions of two ecological hypotheses for the
invention of tool use for insect foraging. We found limited evidence for inter-
and intrasexual differences, as well as temporal variation, in activity budget
and diet. However, differences did not correspond to variation in either rate
of tool use or specialization on tool-based insectivory. Compared to other
populations, orangutans at Suaq Balimbing ate significantly more insects. Low
temporal variation in insectivory and an abundance of social insects at Suaq
Balimbing suggest that
insects formed a staple in the diet rather than a fallback food. Our findings
do not support the hypothesis that tool use is a response to the low
availability of primary food sources. Rather, greater opportunities for
invention likely contributed to insect-extraction tool use at Suaq Balimbing.

Tom Billings