Other Pests and Their Control

Bedbug

• Order: Hemiptera (半翅目);
  • Family: Cimicidae (臭蟲科)
• Commonly found in living room and mattress
• Body oval, bilaterally flattened, wingless
• Adult small (4 to 5 mm), reddish brown
• Possessing piercing and sucking mouthparts
• Stink gland on thorax, producing unpleasant odor
• Female can produce 75 to 200 eggs for whole lifespan (may reach 540 eggs)
• Female lays eggs after a blood meal, with a few eggs being laid per day
• The two common bedbugs are Cimex lectularius and Cimex hemipterus

Cimex hemipterus (熱帶臭蟲)

Life cycle

• Incomplete metamorphosis
  • With egg, nymph and adult stages.
• Egg is white in colour, elongated oval shape, with size ranges from 0.8 to 1.3 x 0.4 to 0.6mm and with a cap at the top.
• Eggs can be found in mattress, furniture, cracks and crevices of wall, floor or ceiling.
• At 18 to 25C, nymphs take about one week to hatch out from eggs.
• Nymphs resemble adults in appearance, but their bodies are smaller and white in colour. Their genital organs are not fully developed and lack of vestigial wings.
• There are five instars in the nymphal stage which take about 14 to 30 days to complete.
• Both nymphs and adults prefer to take human blood
• Life cycle takes 6 to 8 weeks to complete; but it may be extended to 330 days under adverse conditions.
• The life span of adult may reach to 9 to 18 months. 6 to 7 generations could be produced under favourable conditions.

Habits

• Bedbugs live together in groups;
  • Nymph and adult can be detected for heavy infestation
• Bedbugs hold firmly to the cloth or furniture that have close contact to human body while they are taking blood meal,
• Adults need about 10 minutes for a blood meal while nymphs need only about 6 to 9 minutes.
• Adults can survive for 6 to 7 months an even to one year without taking a blood meal.
• They usually hide in dark and dry places during day time.
• Bedbugs will feed in at day time when they are hungry.

Medical Importance

• They cause biting nuisance as some people may suffer sleepless night because of the biting.
• The saliva injected into the wound by bedbugs during biting may cause local inflammation, intense itching to some people.
• Scratching of the swelling after biting by bedbug may cause secondary infections in some people.

Detection

• Their typical hiding places are:
  • Beds, coils of springs, cracks and hollow posts of bedsteads;
  • Upholstery of chairs and sofa
• Spot of fecal materials or blood spot can be detected on pillowcases or mattress
• In heavy infestation, nymphs and adults are frequently found under door and window casings and are also found behinds pictures on the wall
• Present of unpleasant smell

Prevention and Control

• Eliminate cracks and crevices in furniture, walls and floor
• Cleanse the premises including vacuum cleaning regularly
• Avoid using second-hand furniture
• Thorough laundering of bedding and clothing regularly
• Treat furniture, cracks and crevices in floors and walls by using residual insecticides
• Apply hot air / steam or Diatomaceous Earth (DE) directly to the cracks and crevices where the bed bug is found
• Put on proper personal protection when applying insecticides and DE

Flies

Feed on liquid food. Some species, e.g. Stable fly and Horse fly are blood sucking

Common Local Species

Prevention and Control

Environmental Sanitation

• Elimination of breeding places
• Proper collection , storage and disposal of refuse
• Proper protection of animal remains
• Screening of building and protection of food

Related Leaflets

• Effective use of insect electrocuting device
• Advice on Prevention on Fly for Hospitals / Home for elderly

Biting Midges

Biting midges are flies belonging to the family Ceratopogonidae. There are around 6000 species in 125 genera worldwide and more than 1000 known species in China. Four genera, Austroconops, Lasiohelea, Leptoconops and most importantly Culicoides, feed on blood of vertebrates including human.

Insect Biology

The insect undergoes complete metamorphosis. Vicious daytime biting ceratopogonids (such as Lasiohelea taiwana) lay eggs on surface of mud or wet soil, especially those with plenty of decaying plant materials. Biting midge larvae are aquatic or semi-aquatic. Other breeding sites include tree holes, semi-rotting vegetation and the cut stumps of plants.

Adults are about 1-4 mm long with dark body colour. The female feed on blood of mammals. Biting activity varies among species but they are most active in day time or near sunrise and sunset. With short mouthparts, biting midges are unable to bite through clothing and so exposed body parts such as hands, arms and legs are most frequently attacked.

Adults have very short flight ranges, usually less than 100 meters from their breeding grounds. They are most active in shade and in dense vegetation. Despite having a short flight range, dispersal by wind is possible.

Local Situation

In Hong Kong, a total of 33 species of blood sucking ceratopogonids are recorded. Lasiohelea taiwana and Culicoides circumscriptus are examples of common species found in Hong Kong.

Public Health Importance

To most people, the bites of biting midges cause acute discomfort and irritation. The irritation can last for days. Scratching aggravates the pruritus and may lead to bacterial infection. In general, biting midges are not considered as important human disease vectors.

Prevention and Control

Adult midges can be controlled by space spraying of knockdown insecticide to the scrubby and shady area. Regular trimming of densely grown vegetation can reduce resting places for the adults.

Breeding places for biting midges can be extensive and so complete disinfestations of larvae is difficult. Reduction of breeding could be achieved by:

1. keeping the moisture content of soil surface low by techniques like plough or draining.
2. removing refuse, fallen leaves and other decaying vegetation on slopes or on the flower beds as well as choking matters (e.g. muddy soil) in sand-traps/surface drainage channels.
3. trimming, on a regular basis, densely grown vegetation to increase the exposure of soil surface to sunlight and air.
4. applying insecticide at breeding places.

Personal protection measures should be employed, including installation of screens (mesh size <0.75 mm), wearing long-sleeved clothing and applying insect repellents.

Cockroach

Common Local Species

Guidelines on cockroach prevention and control in domestic premises

Fleas

• Wingless blood sucking insect
• Body bilaterally compressed to facilitate movement between hairs and feathers of their hosts
• Powerful hind legs for jumping, can jump 25cm high and 35cm horizontally

Common Local Species

Rat flea (Xenopyslla cheopis) : transmits plague and murine typhus

Cat flea (Ctenocephalides felis) : also attacks human

Prevention and Control

• Control of host animals
• Vacuum cleaning of floor, carpets, etc to clear away all eggs, larvae and pupae
• Spraying of insecticides with residual effect

Tick

• Host animals includes mammals, birds, reptiles and amphibians
• Most of them are blood sucking

Common Local Species

Dog Tick (Rhipicephalus sanguineous)

• Host on dog and other domestic animals, also attacks man
• Transmits Q-fever and Boutonneuse fever

Cattle Tick (Boophilus microplus)

• Host on cattle and other domestic animals, sometime attacks man
• Transmits Q-fever

Prevention and control

• Clearing of bushes along paths, clearing weeds and cutting grass in recreation areas
• Dusting on animals with insecticide dust (e.g. carbaryl dust)
• Residual spraying at infested house

Mites

Dust Mites (Dermatophagoidinae)

• Found in dust
• Free living
• Mainly feeds on human skin detritus.
• Causes bronchitis and dermatitis

Chigger Mites (Trombiculindae)

• Breeds in soil or ground vegetation
• Vector of scrub typhus
• The disease is transmitted by the bite of infected larvae
• Major vectors are Leptotrombidium akamushi and Leptotrombidium deliense
• Guidelines on the Prevention of Scrub Typhus
  (text only version)

Prevention and control

• Maintain the indoor relative humidity below 60%
• Clearing of weeds and ground vegetation
• Use of insect repellent
• Avoid direct contact with bushes

Chironomid

• The adults are mosquito like in appearance, they do not have piercing and sucking mouthparts and therefore non-biting. (Photo)
• Adult chironomids are short-lived, reported to be about a few days.
• Their flight ability is generally weak and they disperse mainly by passive means like wind, vehicles, etc
• Most of the chironomid larvae are aquatic and red in colour. Hence, the larvae are called "blood worms". (Photo) However, a few species are green or yellow.
• Polluted water apparently favours their multiplication and emergence but relatively clean water can also support their breeding. Most of them are detritus feeders.
• Members of this family are quite common in Hong Kong.

Prevention and Control

• Adult midges resting in vegetation, shaded sand traps, indoor environment, etc. can be knocked down by insecticidal aerosol.
• Larvae cannot be suffocated by means of malarial oil.
• Insecticides and larvicides such as B.t.i. can provide better control against the larvae.
• Source reduction and water management are regarded as the fundamental control measures. Drains should be checked regularly to prevent accumulation of water.
• Larvicidal fish is a possible biological agent when the water bodies cannot be removed.
• The nuisance caused by the adult midges can be abated, to a certain extent, by avoiding the use of unnecessary lights at dusk.
• Installation of protective nets and screens of small mesh can ward off intrusion of adult midges into indoor environment.

Guidelines on Prevention of Breeding of Blood Worms in Swimming Pools

List of specimen collection by Pest Control Advisory Section