Somebody on reddit posted a ridiculous picture today of a fly pierced onto a needle of a cactus: http://www.reddit.com/r/pics/comments/xarue/what_are_the_odds_of_this_accident/
Whilst the OP claims the picture to be real, several people doubted the fly could ever reach enough momentum to actually pierce itself onto the cactus.
Using estimates of the appropriate variables needed, could somebody calculate the plausibility of the OP's claim? How would one go about such a calculation? My hunch would be that it can be estimated using the fly's momentum but how can the required piercing force be calculated?