Why is the WiFi IP routed through eth0?

Why is the WiFi IP routed through eth0?

I'm running Ubuntu 13.04 on a BeagleBoard Black (armhf) with an Edimax EW-7811Un wireless USB Adapter. I setup the wireless per https://help.ubuntu.com/community/NetworkConfigurationCommandLine/Automatic
The interface appears to come up:
# ifconfig
eth0      Link encap:Ethernet  HWaddr c8:a0:30:b3:8c:5e 
          inet addr:192.168.1.37  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::caa0:30ff:feb3:8c5e/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2326 errors:0 dropped:0 overruns:0 frame:0
          TX packets:733 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:445340 (445.3 KB)  TX bytes:93413 (93.4 KB)
          Interrupt:56

lo        Link encap:Local Loopback 
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

usb0      Link encap:Ethernet  HWaddr 4a:54:76:2a:4b:9d 
          inet addr:192.168.7.2  Bcast:192.168.7.3  Mask:255.255.255.252
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

wlan0     Link encap:Ethernet  HWaddr 80:1f:02:5c:47:38 
          inet addr:192.168.1.40  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::821f:2ff:fe5c:4738/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1737 errors:0 dropped:0 overruns:0 frame:0
          TX packets:14 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:301418 (301.4 KB)  TX bytes:3048 (3.0 KB)

# iwconfig
wlan0     IEEE 802.11bgn  ESSID:"Messina_2GEXT" 
          Mode:Managed  Frequency:2.437 GHz  Access Point: 20:E5:2A:0C:FC:6D  
          Bit Rate=72.2 Mb/s   Tx-Power=20 dBm  
          Retry  long limit:7   RTS thr=2347 B   Fragment thr:off
          Encryption key:off
          Power Management:off
          Link Quality=64/70  Signal level=-46 dBm 
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:0  Invalid misc:7   Missed beacon:0

lo        no wireless extensions.

eth0      no wireless extensions.

usb0      no wireless extensions.
When connected to the ethernet, I am able to ping the computer:
PING 192.168.1.40 (192.168.1.40) 56(84) bytes of data.
64 bytes from 192.168.1.40: icmp_req=1 ttl=64 time=0.714 ms
But, when I unplug the cable:
PING 192.168.1.40 (192.168.1.40) 56(84) bytes of data.
From 192.168.1.22 icmp_seq=1 Destination Host Unreachable
If I look on my router, I do not see the IP address on the list of wireless devices, but both IP addresses show up as being attached as wired devices.
Does anyone have any ideas what I might have done wrong?