UPSC Prelims 2024 Q18: Environment & Ecology – Biodiversity & Conservation
- (a) Only two
- (b) Only three
- (c) Only four
- (d) All five
Answer: (b) Only three
Explanation
Parasitoid Species — Which Groups Contain Them?
A parasitoid is an organism that lays eggs in/on a host, with larvae developing by consuming the host — eventually killing it. Distinguished from parasites (which don't necessarily kill host).
| Group | Contains Parasitoids? | Details |
|---|---|---|
| 1. Carabid beetles | YES | Some ground beetles (Carabidae) have parasitoid life histories, particularly in subfamily Brachininae. Some beetle larvae parasitise pupae of other insects. |
| 2. Centipedes | NO | Centipedes (class Chilopoda) are active predators, not parasitoids. They kill prey directly. No parasitoid life history known in centipedes. |
| 3. Flies | YES | Tachinid flies (Tachinidae) are the largest family of parasitoid flies. Also phorid flies, some bot flies. Tachinids parasitise caterpillars, beetles, bugs. |
| 4. Termites | NO | Termites (order Blattodea, formerly Isoptera) are social insects that eat wood/cellulose. No parasitoid species known among termites. |
| 5. Wasps | YES | Ichneumon wasps, braconid wasps, chalcid wasps - massive parasitoid diversity. Parasitoid wasps are key biocontrol agents for agricultural pests. |
Parasitoids found in: Carabid beetles (1), Flies (3), Wasps (5) → Three groups → Answer: Only three
Answer: (b) Only three.
Why each option is right or wrong
- (a) Incorrect. 'Only two' would exclude one of carabid beetles, flies, or wasps from having parasitoid species. All three groups contain well-documented parasitoid species.
- (b) CORRECT. Three groups contain parasitoids: carabid beetles (some), flies (tachinid flies, etc.), and wasps (ichneumon, braconid, chalcid wasps). Centipedes and termites have no parasitoid species.
- (c) Incorrect. 'Only four' would include either centipedes or termites — neither group has parasitoid life histories. Centipedes are direct predators; termites are cellulose-feeders.
- (d) Incorrect. 'All five' would include centipedes (direct predators) and termites (detritivores/wood-eaters) — neither has parasitoid members.
Key point
Parasitoids in: Carabid beetles + Flies (tachinid flies) + Wasps (ichneumon, braconid). NOT in centipedes (direct predators) or termites (cellulose eaters). Parasitoid wasps = most important biocontrol agents.
Remember
Parasitoid species are found in carabid beetles, flies (especially tachinid flies), and wasps (ichneumon, braconid wasps). Centipedes and termites have no parasitoid species.
Common mistakes
- Including centipedes as parasitoids — centipedes are venomous predators that kill directly; they have no parasitoid (egg-in-host) life history.
- Including termites — termites are eusocial insects that digest wood/cellulose; parasitism is not a feature of any termite species.
- Forgetting carabid beetles can be parasitoids — while most ground beetles are generalist predators, some have parasitoid larvae that develop inside other insect pupae.
Exam tip
Parasitoid hotspots: WASPS (biggest group — ichneumon, braconid, chalcid = thousands of species), FLIES (tachinid = 10,000+ species), some BEETLES. No parasitoid centipedes or termites. Parasitoid wasps = key organic farming biocontrol.
Sources
- Godfray (1994) — Parasitoids: Behavioral and Evolutionary Ecology
- FAO — Biological Control using Parasitoid Wasps