Me'ila 17 - How Reptiles Meats Combine
There are eight reptiles that transmit ritual impurity . Their blood and meat combine to form the volume of a lentil, and if one eats this volume, he transgresses a full prohibition. They combine to transmit impurity in the same way.
Rabbi Yehoshua stated a general rule: all items that transmits impurity in the same amount (for example, blood and meat of reptiles), and make one impure for the same length of time (one day, until nightfall, in our case), combine. However, if they transmit impurity in different amounts (for example, flesh of a dead human transmits impurity when there is an olive volume of it), or for a different length of time (impurity of a dead human body lasts for seven days) - these items do not combine with one another.
Art: Dirk Valkenburg - Still Life of Fruits from Surinam and Reptiles