Entomology 2

Question 1

Anopheles Transmits

Answer 1

Malaria, Lymphatic filariasis

Question 2

Aedes Transmits

Answer 2

Lymphatic filariasis, Dengue, Yellow fever, Chikungunya, Zika

Question 3

Culex Transmits

Answer 3

Lymphatic filariasis, Japanese encephalitis, West Nile

Question 4

Mansonia Transmits

Answer 4

Lymphatic filariasis

Question 5

Haemagogus Transmits

Answer 5

Yellow fever

Question 6

Mosquito Anatomy

Answer 6

Hard outer shell = exoskeleton (cuticle), three main body parts: head, thorax, abdomen. A pair of antennae and a pair of palps. Forward pointing proboscis. Three pairs of legs, one pair of wings, scales on the wing veins, characteristic wing venation. A pair of halteres

Question 7

Mosquito Head

Answer 7

Proboscis, Antenna, Palp, Compound eye, Occiput

Question 8

Mosquito Thorax

Answer 8

Antepronotum, Scutum, Scutellum, Postnotum, Halter

Question 9

Mosquito Abdomen

Answer 9

Abdominal segments, cercus

Question 10

Mosquito Lifecycle

Answer 10

Adult mosquito emerges from the pupa. Mating soon after emergence. Sperm stored in spermathecae in abdomen to fertilise successive batches of eggs. Both sexes of adults obtain energy from sugary plant juices. Only the female feeds on blood, which leads to egg development. Female searches for appropriate water body for egg laying. Larva hatches soon after eggs are laid or after a delay (species-dependent). Larva swims, feeds, breathes air and develops through four larval stages (=instars). Fourth larval instar metamorphoses into pupa. Pupa swims and breathes air but does not feed. Pupa metamorphoses into adult which emerges at water surface.

Question 11

Mosquito Toxorhynchitinae

Answer 11

One genus only = Toxorhnchites. Very large, metallic green or blue mosquitoes. Females do not feed on blood, proboscis is markedly bent. Larvae are culicine-like but carnivorous, feed on larvae of other mosquitoes. Breed in small water bodies, like tree holes and leaf axils.

Question 12

Mosquito Anophelinae

Answer 12

Three genera, but only one widely distributed = Anopheles. 478 species present around the world. Anopheles are medically very important as they are the sole vectors of malaria, also important as vectors of lymphatic filariasis

Question 13

Mosquito Anopheles gambiae complex

Answer 13

A complex of 9 morphologically indistinguishable species. Anopheles gambiae ss, An coluzzi and An arabiensis are the most important vectors of malaria in Africa (together with An funestus)

Question 14

Mosquito Culicinae

Answer 14

Main medically important genera are Aedes and Culex (and Mansonia). World’s major nuisance biters. Many are important disease vectors transmitting arboviruses and lymphatic filariasis

Question 15

Mosquito Culex

Answer 15

Plain brown body and unspotted legs. End of abdomen not tapered, cerci partially concealed. At least 3 tufts of hair on larval siphon. Major urban nuisance biters. Vectors of lymphatic filariasis and arboviruses.

Question 16

Mosquito Aedes

Answer 16

Spotted/striped legs and body. Tapered end of abdomen, prominent cerci. One tuft of hairs in middle of larval siphon. Often bite during dawn/day/dusk, not at night. Eggs survive dessication. Breed in small containers, tyres etc. Vectors of arboviruses and lymphatic filariasis.

Question 17

Mosquito Mansonia

Answer 17

Spotted legs, scaly wings (‘salt and pepper’ effect), larval siphon adapted for drilling into air spaces in roots/stems of aquatic plants. Vectors of Brugian filariasis

Question 18

Mosquito Anopheline palps

Answer 18

Same length as proboscis M=F, males palps are club shaped (swollen on ends) and antennae are more bushy than female

Question 19

Mosquito Culicinae palps

Answer 19

Female palps much shorter than proboscis. Male palps same length as proboscis, and taper at ends. Male antennae are more bushy than female

Question 20

Mosquito Behaviour related to disease transmission

Answer 20

Some species enter houses to feed (endophagic), others bite outdoors (exophagic). Resting places during day to digest meals: indoors (endophilic) or outdoors (exophilic). Prefer to feed on humans (anthropophilic), animals (zoophilic), or opportunistic. Aedes aegypti (vector of yellow fever) is anthropophilic, exophagic and exophilic. Anopheles gambiae (African malaria vector) is anthropophagic, endophagic, endophilic. Few species entirely anthropophagic/zoophagic, endophagic/exophagic, or endophilic/exophilic. The terms are relative, and behaviour plastic or opportunistic to some extent. Biting times also important to transmission. Anopheles gambiae bites late at night after people are asleep. Anopheles culicifacies (India) in late evening). Resting behaaviour (indoors vs outdoors) important for control

Question 21

Mosquito Summary

Answer 21

Mosquitoes are responsible for some of the world’s major infections diseases. Large variability in species, each with different behaviours and ecology, representing very different ecological niches. Need to understand these differences to control mosquito-borne diseases. Major differences exist in morphology, behaviour and ecology between anophelines and culicines.

Question 22

Mosquito Aedes aegypti

Answer 22

Body is black and white patterned. White lyre shape on top of thorax. Day biting, Vector of dengue, urban yellow fever, zika and chikungunya. Where as Aedes albopictus has single white line