Starving Spiders

The spider species, Anelosimus eximius, lives in South America in large colonies. Some of these colonies consist of tens of thousands! Their colonies grow to be so large because the spiders will remain in the nest in which they were born from one generation to the next. These species nest together, create a web together, and capture their prey together. The problem comes when the colonies become too large because these spiders eventually run out of food. The lack of food leads to massive die-offs. The problem also arises when the spiders capture prey that is far too big for any one spider to feed on. This overshare of food is a danger to the species. Researchers have found that about 21% of these colonies go extinct every generation. 

Black Piranha

The black piranha can be found all over the Amazon Basin. It is also the most widely spread piranha in South America. Suprisingly, the black piranha and the extinct, giant piranha (megapiranha) have the most powerful bites of all carnivorous fish. The piranha's specialized jaw morphology allows them to attack and bite chunks out of larger prey. The piranha has a relatively small size, but its aggressive nature and accessible population make it a worthy predator. Diet studies indicate that piranhas will attack and bite chunks of bony fins and flesh from prey many times larger than themselves.
The black piranha is able to bite with a force more than 30 times greater than its weight. The bight is achieved by the large muscle mass of the black piranha's jaw and the efficient transmission of its large contractile forces through a highly modified jaw-closing lever.
The bite force of the extinct, giant piranha, was reconstructed and discovered to be stronger than other extinct mega-redators, including the whale-eating shark.
http://www.sciencedaily.com/releases/2012/12/121220160727.htm
http://www.aquascapeonline.com/aquatic-live-stock-fresh-water-fish-piranhas-genus-serrasalmus-black-piranha-guyana/