In which of the following kinds of organisms is a dramatic phenomenon observed in which, after copulation, the female often kills and eats the male partner?

Introduction / Context:
In the animal kingdom, mating behaviour can be extremely diverse. One striking and much discussed behaviour is sexual cannibalism, where one partner, usually the female, kills and sometimes eats the male after or even during copulation. This question asks you to identify the type of organism in which this phenomenon is classically and widely observed.

Given Data / Assumptions:

We are focusing on a phenomenon where the female kills the male after copulation. Options list different kinds of animals: dragonfly, honey bee, spider, pit viper and earthworm. We assume typical textbook and documentary examples used to illustrate sexual cannibalism. The question refers to a well known, not rare, example.

Concept / Approach:
Sexual cannibalism is most famously documented in certain spiders, such as the black widow and some orb weavers. In these species, the female may attack, kill and even eat the male during or after mating. This behaviour is thought to provide nutritional benefits to the female and sometimes to increase the chances of successful fertilisation. While other groups, like some mantises, also show sexual cannibalism, spiders are the classic and commonly cited example in basic biology courses. The other listed animals do not typically show this extreme post mating killing of the male in the same way.

Step-by-Step Solution:
Step 1: Recall well known examples of sexual cannibalism from biology textbooks and nature documentaries. Step 2: Identify spiders, particularly black widows and some garden spiders, as classic examples where the female may kill the male after mating. Step 3: Check dragonflies, which have complex mating behaviours but do not usually involve the female killing the male. Step 4: Remember that in honey bees, the male drone may die after mating due to loss of reproductive organs, but the queen does not actively kill and eat him. Step 5: Recognise that pit vipers and earthworms do not show this type of post mating cannibalistic behaviour as a standard pattern.

Verification / Alternative check:
To verify, think about how sexual cannibalism is introduced in ecology and behaviour chapters. The first examples almost always include female spiders and preying mantises. Among the options provided, only spiders match this conventional illustration. Honey bees do have dramatic mating deaths for males, but caused by physical damage rather than deliberate killing by the female and there is no cannibalism. Dragonflies, pit vipers and earthworms are not associated with this specific behaviour in standard teaching material, which confirms spiders as the correct answer.

Why Other Options Are Wrong:
Dragonflies show elaborate courtship and mating flights, but females do not routinely kill and eat males after copulation. Honey bee drones die after mating because their endophallus is torn away, not because the queen kills them, and there is no feeding on the male. Pit vipers are solitary reptiles whose mating behaviour does not include regular sexual cannibalism by females. Earthworms are hermaphroditic animals that exchange sperm and separate again; they do not kill each other after mating. Thus, these options do not fit the description of female driven post mating killing and cannibalism.

Common Pitfalls:
A common mistake is to focus on the fact that honey bee drones die after mating and assume that this means the queen kills them, which is not accurate. Another pitfall is to forget that the question emphasises both killing and, typically, feeding on the male, which is characteristic of sexual cannibalism. To answer correctly, always associate classic sexual cannibalism examples with spiders, especially the black widow, whenever such questions appear in exams.

Final Answer:
The phenomenon where the female often kills the male after copulation is most famously observed in spiders.