If you are talking about actual mass size, the quadriceps and hamstrings would be the largest muscle group in the body.
Largest!
The triceps are the largest muscle group in the arm. So, if you want big upper arms, concentrate on working your triceps rather than working your biceps. .
ambot
Atomic size increases down a group as the energy level (or shell) increases. So Astatine will have the largest size (radius) in group 17
The age group that experienced the largest increase in the male-female ratio from 1990 to 2000 was likely the senior population, typically age 65 and over. This age group tends to have a higher proportion of females due to longer life expectancy, leading to a larger increase in the male-female ratio as the population ages over the decade.
The hamstring muscle group (biceps femoris, semitendonosis, semimembranosis) are the antagonists to the quadricep group.
A skeletal muscle
The scapula is not a muscle; it is a bone.
If you were talking about resistance training, the only measurable difference in size immediately after a strength training session would occur if you deliberately trained in such a way as to experience a "pump" in a muscle group. For a few minutes, that muscle group would be engorged with blood and might be slightly larger than normal. Of course, in the long term proper resistance training will increase your amount of lean muscle mass and that may (at least in men) increase the size of muscles.
Muscle is an organ! An organ is made up of a group of tissue and muscle is made up of a group of tissue! So muscle is an organ sure! Just me!
Insects are the largest group of arthropods.