1. Basic Shapes

Create an ellipse using elliptical shape tool.



Enable "add to shape area" at the top bar. Create a rounded rectangle using rounded rectangle shape tool.



Press Ctrl+T. Right Click and select Warp. Select "Shell Lower" from the preset warp shapes at the top. Adjust the settings as shown.


2. Aliens Have Flexible Bodies






Select the lower path using path selection tool . Press Ctrl+T. Scale down horizontally.




Select the lower path using path selection tool. Press Ctrl+T. Right Click and select Warp. Adjust the nodes as shown.




With "add to shape area" enabled at the top bar, draw legs with feet using pen tool.






Type "S" using staccato or a similar font. 



Use this "S" as an arm of the alien bug. Duplicate the layer. Press Ctrl+T. Right click and select Flip Horizontal and place on the other side.



Double click the layer to open layer style window. Apply settings as shown.



Apply same layer style to the whole body.



Duplicate the body layer and fill with a solid dark color.