The year that Oliver was a spider, Owen was a bat. Bea was just under a year old and I was very busy with twin 5 year olds and a mobile little one, so there was not a lot of time for elaborate costumes. Like the spider, this one is quite easy. I bought about a yard of black flannel. In keeping with my "do the least possible while still making a costume" attitude I folded it in half diagonally and cut it into two triangles. I dug up some foam* that Adam had used for another project and cut eight long strips which I placed on the triangles to create sections. I placed two of the strips on the outer edges of the wings and folded the fabric over it, sewing it to secure. I used the remaining pieces to divide each wing into thirds, and cut strips from a remnant of a dark patterned fabric which I sewed over the foam to conceal it.
*NOTE - If you do not have a big piece of foam lying around I am sure other things would work for this...the idea is to simultaneosly give the wings some structure and make them a little more life-like and visually interesting. I bet thin strips of cardboard would work pretty well in a pinch.
Once the basic wing structure was complete I used pinking shears to cut arcs between the foam points (see detail above left). Once the two wings were done I sewed them together and attached another scrap of fabric in the center so it could tie around the neck like a cape. I sewed black elastic along the outer edges so that the wings could be attached at the wrists and ankles (photo above right). Note: The photo of Owen wearing the bat wings was taken last week...the "wrist straps" are now practically at the elbows, and the "ankle straps" did not even come close to fitting around his ankles! If you make this costume make the wings first and then hold them up to your child to see where the elastic needs to be added.