  Spatially resolved spectroscopic data from the CIRPASS integral field unit
(IFU) on Gemini are used to measure the gravitational lensing of the 4-image
quasar Q2237+0305 on different size scales. A method for measuring the
substructure present in the lens using observations at multiple wavelengths is
demonstrated to be very effective and independent of many of the degeneracies
inherent in previous methods. The magnification ratios of the QSO's narrow line
region (NLR) and broad line region (BLR) are measured and found to be disagree
with each other and with the published radio and mid-infrared magnification
ratios. The disagreement between the BLR ratios and the radio/mid-infrared
ratios is interpreted as microlensing by stars in the lens galaxy of the BLR
The disagreement between the radio/mid-infrared ratios and the NLR ratios is
interpreted as a signature of substructure on a larger scale, possibly the
missing small scale structure predicted by the standard cold dark matter (CDM)
model. Certain combinations of the radial profile and the substructure surface
densities are ruled out using extensive lensing simulations. A substructure
mass scale as large as 10^8 M is strongly disfavored while 10^4 M is too small
if the radio and mid-infrared emission regions have the expected sizes of ~10
pc. The standard elliptical isothermal lens mass profile is not compatible with
a substructure surface density of < 280 M/pc^2 at the 95% confidence level.
This is 4-7% of the galaxy's surface density (depending on which image position
is used to evaluate this). The required substructure surface density at the
required mass scale is high in comparison with the present expectations within
the CDM model.
