Sorting Arthropods into Insects and Arachnids has become very popular; this work is a combination of conceptual sorting and a basic math work. It requires the child to count the legs and body parts of the arthropod and use this information to sort them based upon their taxonomic description (insects have six legs and three body parts, arachnids have eight legs and two body parts)- a pretty high level cognitive operation for these two and three year olds!
Children also enjoy the larger work of sorting Arthropod three part cards into their taxonomic classes (some children have also experimented with their own classification schemes- including arthropods that bite people and arthropods that do not! An important consideration, I agree!).
The children also enjoy trying to identify the hidden Arthropods in camouflage cards (and often play games outside in which they try to hide arthropods cut out of construction paper from their classmates by applying the concept of camouflage).
The children love learning the nomenclature associated with the metamorphosis of arthropods.
And, of course, for the children who have acquired the motor control needed for handwriting, there are lots of opportunities for copy writing (coping text for handwriting practice).
These works are examples of the ways in which Montessori cultural units begin by providing the child with a concrete sensory experience and then permit them to actively construct meaning around the information they have been presented with (rather than passively memorizing facts); additionally, these cultural units reinforce and inter-relate with the traditional Montessori materials by providing additional motives (more practice and repetition) for the child to engage in math, language, and handwriting tasks.