When Raj examines the jar with the cricket, he sets it down on the table with his fingers still resting on it. It then cuts to a different angle and he isn't touching it. Then when Raj preps his bagel, the amount of cream cheese on it changes between shots.
When Crawley starts to walk over to the dung beetle cage, his hair is all combed back. In the next shot, there is some hair hanging over his right temple.
Professor Crawley states that he can identify every species of insect and arachnid on the planet. Although new species are discovered at a rate of several hundred a year, he is not speaking literally, since he mentions that he has been studying insects since he was eight and has twenty years of experience as an entomologist, so he just means that identifying the species that have already been discovered comes relatively easy for him.
Howard claims a cricket they've caught is a common Field Cricket, while Sheldon is sure it's a Snowy Tree Cricket. Field Crickets are dark brown and robust-looking whereas Snowy Tree Crickets are pale green and delicate, as different as buffalo are from gazelles. If that at first wasn't obvious enough, then the photos found by Howard in a reference guide should have promptly settled the argument.
When Raj points out to Sheldon that chickens can't climb trees, Sheldon replies "thank god", which is strange since Sheldon is an atheist.