"Insect" - what is it, definition of the term
Insects constitute a class of hexapod arthropods distinguished by a segmented body divided into head, thorax, and abdomen, three pairs of jointed legs attached to the thorax, and typically one or two pairs of membranous wings; respiration occurs through a network of tracheae, and development follows either incomplete or complete metamorphosis. Within the broader arthropod group, ticks belong to the arachnid subclass and lack the three‑leg pair configuration, while lice and fleas represent parasitic members of the insect class that have specialized mouthparts for blood feeding; the term «true bugs» refers specifically to members of the order Hemiptera, characterized by piercing‑sucking mouthparts and a hemelytron wing structure.
Detailed information
The class of small, segmented arthropods includes a variety of blood‑feeding and plant‑feeding organisms that affect human health and agriculture. Ticks are ectoparasitic arachnids with a hard dorsal shield; they attach to hosts for several days, ingesting blood and transmitting pathogens such as Borrelia burgdorferi, the causative agent of Lyme disease. Their life cycle comprises egg, larva, nymph, and adult stages, each requiring a blood meal to progress.
True bugs belong to the order Hemiptera and are characterized by piercing‑sucking mouthparts. Many species, such as aphids and shield bugs, feed on plant sap, causing wilting, stunted growth, and the spread of viral diseases. Some aquatic representatives, like water striders, display surface‑tension locomotion without direct agricultural impact.
Lice are obligate ectoparasites of mammals and birds, classified in the order Phthiraptera. They exhibit a flattened body adapted for clinging to hair or feathers. Human head lice («Pediculus humanus capitis») lay eggs (nits) on hair shafts, and infestation leads to itching and secondary skin lesions. Body lice («Pediculus humanus corporis») can transmit bacterial agents such as Rickettsia prowazekii.
Fleas are wingless, laterally compressed insects that specialize in jumping. Their powerful hind legs enable rapid movement between hosts. The cat flea («Ctenocephalides felis») and the human flea («Pulex irritans») are common vectors for Yersinia pestis, the bacterium responsible for plague, and for various tapeworms. Flea life stages—egg, larva, pupa, adult—occur in the environment, allowing populations to persist without a host for extended periods.
Key distinguishing features:
- Ticks: arachnid, four pairs of legs, hard or soft scutum.
- Bugs: hemipteran, rostrum for sap extraction, two pairs of wings (often partially hardened).
- Lice: wingless, body flattened, claws for hair attachment.
- Fleas: wingless, laterally compressed, powerful hind legs for jumping.
Understanding morphology, life cycles, and disease transmission mechanisms is essential for developing targeted control strategies across agricultural, veterinary, and public‑health sectors.