Crustacea, arachnidae and insecta (Phylum arthropoda) actually have an open respiratory system. This is known as tracheal system. This means that oxygen is delivered directly to cells via air tubes (since its an open system) which is highly efficient. This allows for a high metabolic rate, but limits body size. An increase in met rate allows for flying (insects). Some spiders also have the adaptation of book lungs, which delivers oxygen from a slit in the body surface, through the "lung" and into blood-filled chamber. This adaptation allows for better uptake of oxygen, compared to the tracheal system, and allows for greater body size.
Hope this helps - theres lots more to it, but this is some basic info to get you started
Answers & Comments
Verified answer
Crustacea, arachnidae and insecta (Phylum arthropoda) actually have an open respiratory system. This is known as tracheal system. This means that oxygen is delivered directly to cells via air tubes (since its an open system) which is highly efficient. This allows for a high metabolic rate, but limits body size. An increase in met rate allows for flying (insects). Some spiders also have the adaptation of book lungs, which delivers oxygen from a slit in the body surface, through the "lung" and into blood-filled chamber. This adaptation allows for better uptake of oxygen, compared to the tracheal system, and allows for greater body size.
Hope this helps - theres lots more to it, but this is some basic info to get you started