"sand flies" / biting midges

Introduction

Australian tiny “sand flies” (biting midges) can cause delayed onset intense itching and inflamed skin can be problematic in certain coastal areas, especially where there are large areas of tidal sand flats, estuaries, lagoons or mangrove swamps
these are of the family Ceratopogonidae, better known in America as “no-see-ums” - hence the camping mesh sizings for tents are now usually small enough to exclude these insects hence no-see-um mesh
- most belong to the genus Culicoides
  - the dominant pest in NSW is Culicoides subimmaculatus
  - elsewhere in Australia, it may be Culicoides ornatus and C. molestus
- a biting midge belonging to the genus Leptoconops appears in the sandstone gulleys of the Berowra-Bobbin in NSW in Oct/Nov and tends to bite aroud the hairline and even near the eyes during the daytime
they are very small flies (0.5mm–4mm long)
- until they move, they could be mistaken for a speck of dirt on your skin
they are one of the most difficult groups of insects to control
most people are unaware they are being bitten at the time
they are not known to transmit any disease-causing pathogens to humans but do transmit disease to animals
there are over 5000 species of Ceratopogonidae distributed throughout the world except in polar regions

New Zealand have very different “sandflies” which are actually “blackflies” and these are extremely troublesome in some areas
- the New Zealand blackfly (Austrosimulium australense), found in the North Island and coastal areas of the South Island
- the West Coast blackfly (A. ungulatum), found in the South Island only, mainly the west coast around Jackson Bay / Queenstown / Fiordland and Milford Sound area as well as Nelson
  - they bite anywhere there is skin including scalp, making tiny slashes and their bite results in pain which is short, sharp and surprising and then about 12-18 hours later, intense itching due to histamine applied by the fly and you can get dozens of bites per minute if you have exposed skin
  - they are only active when relative humidity exceeds 60% and are especially abundant at edges of the forests near streams or near beaches
  - they seem to be attracted to dark clothing, especially black, blue and red so wear very light colored clothing
- A. tillyardianum, found on both islands between Auckland to just north of Dunedin, although not in great numbers.
in the USA in addition to No-See-Ums found in Florida and other areas, sandfly may refer to certain horse flies that are also known as “greenheads” (family Tabanidae)
NB. true sand flies are a DIFFERENT, more dangerous group of tiny biting insects in the subfamily Phlebotominae but are NOT found in New Zealand or the Pacific islands despite these being within their latitude range of 40°S to 50°N¹⁾
- in Australia, the Australophlebotomus, Idiophlebotomus and genus Sergentomyia exist especially in caves in Queensland and although they are also found elsewhere in Australia, they are not known to transmit the dangerous disease Leishmaniasis but are mainly adapted to breed with bats and reptiles²⁾.

Symptoms of bites

only the female midge will bite and has piercing and sucking mouth parts, which suck blood and cause the classic allergic response as saliva is injected to prevent blood clotting
- the allergic response tends to be worse for tourists as the locals tend to develop allergic tolerance
the bites will initially cause small red or pink dots
itchiness usually begins 12-24hrs after the bite and may last several days
these may then develop into very itchy allergic reactions which can include blisters and raised wheals
- the delayed reaction pa-pule may subside within two to four days with only mild irritation, or may develop into a more persistent vesicle capped by a scab

Life cycle

Ceratopogonidae are holometabolous, meaning their development includes four life stages: egg, larva, pupa, and imago or adult.
females lay their eggs en masse on the edge of water bodies (usually in tidal areas but above the level of the neap tide, but can be in freshwater creeks) - in the sand flats, moist decaying leaf material, damp dirt or mud in estuaries, lagoons, mangrove swamps and creek beds
- coastal developments such as canal estates provide favourable conditions for biting midges
lifecycle includes a worm-like (larval) and cocoon-like (pupal) stage (lasts 3-7 days) before the adult emerges in 3 to 10 weeks and this requires a high moisture content in the surrounding area
- Larvae need moisture to develop, but also air and food.
emergence of adult biting midge is associated with the new and full moon phases when tidal range is greatest, especially for midge species breeding in intertidal coastal areas.
- mass attacks may occur no more frequently than fortnightly (in NSW, in summer and autumn)
- mass emergences will not occur at every neap tide even when the weather is warm
adults can live for several days to months depending on the species.
They can be trapped by luring them with carbon dioxide.
when they leave the ground they settle in vegetation waiting for some exposed skin to come by and generally only fly low to the ground
biting activity of midges is mainly limited to periods of dawn and dusk and they are attracted to shady humid areas
similar to female bush flies getting protein from tears, the female sand flies use the blood they obtain from sucking as protein for developing a batch of eggs
their activity significantly increasing when humid temperatures are between 27-32 degrees Celsius
may continue to bite through the night and during overcast days
often remain inactive through windy weather, finding shelter amongst shady vegetation
they usually disperse only short distances (usually 500m but may be 5km blown inland along with winds) from their breeding sites

Prevention of bites

avoid known sandfly areas especially at dusk and dawn
wear protective clothing including long sleeves, pants, shirt with collar and closed-in shoes
apply or picaridin or 15-25% DEET for adults (up to 10% on children aged over 12 months) to any exposed skin - especially neck, scalp and ankles
when indoors use ceiling fans to create wind
use no-see-um mesh for windows/doors

Treatment of bites

there is a suggestion from some that at the early period after a bite, heating the skin to 51degC with a device such as a “bite away pen” will denature the saliva proteins and reduce the inflammatory response but this temperature could easily burn the skin too!
cold compresses
antihistamines
avoid scratching as this may cause secondary infection
calamine lotion and Aloe Vera gels are also popular

¹⁾

https://resjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2915.2012.01034.x

²⁾

https://pubmed.ncbi.nlm.nih.gov/1841207/

Table of Contents

"sand flies" / biting midges

Introduction

Symptoms of bites

Life cycle

Prevention of bites

Treatment of bites