Deer Fly

Deer Fly

Deer flies are a small but mighty nuisance for tourists visiting Nepal. These aggressive insects, belonging to the genus Chrysops, are found in many parts of the country and are known to deliver a painfully itchy bite. While deer flies themselves do not carry diseases, their bites can certainly put a damper on enjoying Nepal's natural beauty and trekking its mountain landscapes.

For tourists unfamiliar with these pesky insects, it's important to be aware of deer flies in Nepal so you can avoid them and properly treat their irritating bites should you have the misfortune of being bitten. Deer flies range from just 3-7 mm long but have a painful bite disproportionate to their tiny size. 

Deer flies are tenacious in their pursuit of a blood meal. Once they sense carbon dioxide, heat, and movement from animals or people, they will attack exposed skin aggressively. Their bites often bleed and swell due to the anticoagulant in their saliva. Though not medically dangerous, they inflict a bite that itches intensely, often for multiple days afterward.

By learning how to prevent deer fly bites and treat them should prevention fail, tourists can still fully enjoy Nepal's stunning treks through valleys and hills, rafting trips down rushing rivers, and wildlife safaris hoping to spot tigers, rhinos, elephants, and other exotic animals. A few precautions and some topical creams in your travel med kit will help you steer clear of deer flies so you can revel in Nepal's natural grandeur.

Identifying Deer Flies

Deer flies are relatively small insects, ranging from just 3-7 millimeters in length. Their bodies and wings are typically light brown, dark brown, or black. They have colorful eyes, often brightly patterned greens, purples, reds, and oranges.

Distinguishing features of the deer fly include their dark bands across the wings and the dark veins running through the wings. The wings themselves have a characteristic transparent section near the tip. The antennae are short and pointy. Deer flies have six long legs for clinging to surfaces. The mouthparts of females are designed to pierce skin, while males have large eyes that meet at the top of the head.

The most definable trait of the deer fly is its aggression towards warm-blooded animals like mammals and birds. It zones in on carbon dioxide plumes, heat signatures, movement, and exposed skin as cues to fly in quickly and bite. No other flies or lookalike insects share this unrelenting blood-sucking behavior.

Other flies like horse flies and stable flies come from different genera than deer flies. Horse flies are much larger, around 1-2.5 cm long. Stable flies also pursue blood meals but do not behave as aggressively as the aptly named deer fly. Mosquitoes are considerably smaller than deer flies and have longer mouthparts designed for piercing fabric to access skin. No see ums are tiny gnats just 1 mm in size. So while the deer fly has some lookalikes, its aggressive human-biting behavior makes it simpler to identify.

Areas and Seasons of Prevalence

In Nepal, deer flies thrive in warm, wet environments during the hottest summer months. They are most commonly found in forested areas like jungles and wooded trails. Wetlands and marshy areas also provide ideal breeding grounds. Deer flies start to emerge in late spring and their numbers peak during the summer rainy season from June through August.

Areas at lower elevations tend to have the highest deer fly populations, as they provide warmer weather that allows quicker reproduction cycles. The Terai lowlands in southern Nepal that border India are prime deer fly territory. Chitwan National Park and Bardia National Park, known for their thick forests, wetlands, and grasslands, have notoriously high deer fly populations during summertime.

Mid-hills and foothills areas like the Annapurna Conservation Area and areas in and around the Kathmandu Valley also have deer flies present but generally in lower numbers than the tropical southern plains. They are still problematic near rivers, lakes, or moist woodlands. Summertime trekkers and safari-goers in these areas need to take precautions against deer flies as well.

By autumn, cooler temperatures cause deer fly numbers to rapidly dwindle. Very few deer flies are spotted from September to November. But come the next spring, their populations will begin to surge again, starting the seasonal cycle anew. So while the wet summer months see hordes of aggressive deer flies, other times of the year provide largely deer-fly-free visits.

Health and Safety Concerns

While extremely annoying, deer flies do not spread any known diseases to humans or animals they bite. However, their bites can still pose health issues due to the pain, swelling, and potential infection or allergic reaction.

Typical deer fly bites produce painful, red welts on the skin surrounded by hives or hardened swelling. The welts tend to be slow-healing and itch intensely, often for a week after being bitten. The area may feel hot to the touch due to inflammation brought on by the fly’s saliva. Some bites bleed in the center due to blood vessels rupturing from the piercing mouthparts. Scratching deer fly bites open increases risks of bacterial infection.

In rare cases, some sensitive individuals may have an allergic reaction to compounds in the deer fly’s saliva injected during biting. Reactions can include exaggerated swelling at the bite site extending past the welt. Larger body hives and changes in blood pressure or heartbeat could also occur. 

The most severe allergic reactions progress to anaphylactic shock requiring immediate medical intervention to regain normal breathing and reduce rapid pulse.

Signs of common deer fly allergies include excessive redness/swelling, hives on areas beyond the bite, swollen lips/eyelids, dizziness, shortness of breath, increased heartbeat, stomach cramps, or fainting. Any indications of a widening reaction point to the need for swift medical care to address the allergic response. Carrying allergy medications can help in minor cases when medical care is unavailable. However, anaphylaxis requires professional emergency assistance.

Prevention and Protection

The best way to avoid misery from deer flies is to prevent their painful bites in the first place when visiting Nepal. Protecting exposed skin is key, so wearing long sleeves, long pants tucked into socks, and hats provide a basic barrier. Light colors also attract fewer flies looking to land and bite darkened silhouettes.

Insect repellents containing DEET, picaridin, IR3535, or oil of lemon eucalyptus can be applied to clothing and any exposed skin following product instructions. Reapplication is necessary every few hours. Permethrin-sprayed gear offers longer protection when dried, useful for hiking boots and outer layers.

When outdoors in wet, wooded areas during summer months, vigilant deer fly awareness is a must. Move slowly and avoid directly swatting at landing flies, which further incites attack. The use of netted hats and head coverings provides additional guarding. Taking frequent breaks in sunlit openings where flies are less active can also provide some respite.

Inside accommodations, ensure window screens have no tears where flies could enter. Keep doors closed as much as possible. Ceiling fans and air conditioning also deter fly activity indoors. Screened shelter areas for dining or relaxation are safer than open-air patio seating.

Staying knowledgeable about deer fly habits, seasons, and hotspots allows smart planning of travel dates and destinations to minimize exposure. But during peak summer sightseeing, sufficient precautions are a requirement to foil the bothersome deer fly.

First Aid and Treatment

If bitten by a deer fly, immediately washing the area with antimicrobial soap and water helps reduce the risk of infection. A cold pack or wrapped ice can then be applied to ease swelling and itching. Over-the-counter hydrocortisone cream on the welt also lessens irritation. Ibuprofen or antihistamines manage wider-spread reactions.

Seek prompt medical care if excessive swelling, wounds, symptoms beyond the bite site, or signs of infection develop. Infected bites turn increasingly red, swollen, and warm days later as pus and fever may emerge. Any indications of a severe allergic reaction also require emergency care, like trouble breathing, plummeting blood pressure, or loss of consciousness.

To speed healing, avoid scratching bites even though they itch severely. OTC creams with pramoxine provide relief without scratching. Applying baking soda or milk of magnesia pastes dries oozing blisters too. For swollen itchy hives, calamine lotion cools on contact. Oral antihistamines taken daily, like Claritin or Zyrtec, also calm body-wide reactions for up to a week following bites.

While largely just a nuisance danger, deer flies can still negatively impact travel experiences. Carrying a small first aid kit with anti-itch creams, ice packs, antihistamine tablets, and antibiotic ointment enables properly treating bites to continue enjoying Nepal’s natural splendors undeterred.

Impact on Outdoor Activities

For adventurous travelers hoping to trek and camp through Nepal’s breathtaking landscapes, deer flies present an obnoxious obstacle during the summer months. The insects are attracted to the carbon dioxide, warmth, and perspiration that come with exertion during hiking, climbing, river rafting, and wildlife viewing on safaris. They will bite through lightweight activity clothing to access skin. Their bites can cumulatively ruin an otherwise idyllic experience in nature.

Preparations must be made to protect against deer flies while doing outdoor activities in Nepal. Closely woven, loose lightweight pants and long sleeves treated with permethrin offer a protective barrier. Zip-off leggings converted to sleeves after cooling down from a hike deter bites on warmed limbs. Hats with mesh netting provide vital facial protection.

Camping in open areas away from tree lines and brush reduces deer fly populations that breed in adjacent wooded zones. Quickly moving into tents zipped closed also limits biting flies' access. Wearing insect repellent even under clothing produces an emanating aura of protection while active outside.

While deer flies cannot be fully prevented across the Nepali landscape in summer, smart defenses let outdoor enthusiasts continue to revel in the majesty of the Himalayas relatively unmolested. A few bothersome bites may still find their mark but are a small price to pay for the glories of Nepal.

Myths vs Facts

Several misconceptions exist about the irritating deer fly. Clearing up this inaccurate information with factual clarity allows for properly addressing the summer scourge.

Myth: Deer flies spread disease to humans like mosquitos.

Fact: Unlike mosquitos, there are no identified pathogens or parasites transmitted by deer flies that make humans sick. Their bites just inflict painful swelling and itching.

Myth: Deer flies only reside near deer populations and wooded areas.

Fact: While forests and deer offer prime targets for the blood-feeding flies, they inhabit a variety of environments and bite any warm-blooded animal available, including humans.

Myth: Deer fly bites are just a minor nuisance.

Fact: The undeservedly vicious bites have sent children, pets, and adults into tears or shock from their sheer intensity. The ensuing week of agony and large reactions can be debilitating.

Myth: Insect repellents are fully effective against deer flies.

Fact: Deer flies are so persistent in pursuit of blood meals that most insect repellents are only somewhat effective as a deterrent. Combinations of barriers and chemical repellents are best.

Knowing truths versus tall tales about the tiger-striped pest allows smart preparation for traveling Nepal’s countryside. While deer flies seem intent on spoiling summer adventure, outsmarting them with facts secures the warm season for fun minus the fright.

Useful Contacts and Resources

Should a deer fly bite or other insect sting during travel in Nepal produce concerning symptoms beyond a minor reaction, several resources assist.

For emergencies like anaphylaxis or infections requiring antibiotics, call the national hotline at 102 for police dispatch of an ambulance to the nearest hospital. In remote areas, ranger stations in parks may also have emergency transport and radio/satellite phones to call for urgent help.

Travel clinics at CIWEC Clinic Travel Medicine Center (+977 1 4424111) or Global Doctor (+977 1 42619661) in Kathmandu have expatriate doctors available for non-critical insect bite care. They also provide pre-travel health advice to avoid insect dangers.

For more trip planning details on insect risks like deer flies by region, the US CDC Nepal travel page outlines specific altitude, season, and habitat guidance at The safari outfitter website also lists monthly insect hazards across Nepal’s parks and trekking zones.

Staying informed about medical access paired with advisory deer fly patterns by locality allows proper appreciation of Nepal’s natural beauty with minimal pest interference. Seeking timely care for any escalating reactions permits focusing on the journey, not the nuisance bugs en route.


Deer flies may seem like insignificant pests, but a proper understanding of how to prevent and treat their painful bites allows fuller enjoyment of Nepal’s majestic outdoors. Key protective measures tourists should remember include wearing lightly colored clothing with long sleeves and pants, using insect repellents, staying aware of deer fly habits in forest and wetland areas, and having first aid supplies on hand. Staying at higher elevations and visiting during spring or fall months also reduces risk.

While deer flies pose an annoyance, the natural splendor of Nepal’s soaring peaks, abundant wildlife, and rich cultural traditions promises immense rewards for visitors. With the Himalayas offering some of the most stunning vistas and trekking routes in the world, tolerating a few pesky deer flies is a small concession. Focusing on the journey rather than any temporary insect irritants guarantees to find inspiration amid Nepal’s scenic grandeur. Let respect for the deer fly’s domain give way to reveling in Nepal’s magnificence.