Question

Three segmented antennae located in deep grooves is the characteristic feature of order
(A) Protura
(B) Diplura
(C) Collembola
(D) Siphonaptera
Choose the correct answer from the options given below:

• A. (A) and (B) only
• B. (D) only
• C. (A), (B), (C) and (D)
• D. (C) only

Hint:

Ectoparasites like fleas (Siphonaptera) have streamlined body shapes. Concealing their three-segmented antennae in deep cranial grooves is an adaptation to glide through host fur or feathers without resistance.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Antennal structure and positioning are key diagnostic keys used to identify and classify insect orders.
Some wingless or highly specialized ectoparasites have modified antennae that can be concealed to prevent damage during movement.
Detailed Explanation:
- Siphonaptera (D): This order consists of fleas, which are laterally compressed, wingless ectoparasites.
To facilitate smooth movement through the hair or feathers of their hosts, fleas have highly modified, short, three-segmented antennae.
These antennae are housed in deep lateral protective grooves (antennal fossae) on the head, preventing them from being damaged or causing drag during locomotion.
- Protura (A): These primitive hexapods completely lack antennae.
- Diplura (B): They possess long, filiform, multi-segmented antennae.
- Collembola (C): They have four-segmented antennae that are not concealed in deep grooves.
Thus, only statement (D) is correct.

Step 2: Final Answer:
The presence of three-segmented antennae located in deep grooves is characteristic of Siphonaptera, corresponding to option (2).