6.1 Arthropods 1 Flashcards
Arthropods ‐ General Characteristics
jointed appendages
chitinous exoskeleton
body segmented
separate sexes
Classes of Arthropods (that we cover in this course)
- Insecta - insects
- Arachnida ‐ mites, ticks, spiders
Characteristics of Insects
- 3 body divisions
‐ head, thorax and abdomen - 3 pairs of legs
- sometimes wings (usually 2 pairs)
Diptera - what are they
Two Winged Flies
* Mosquitoes, gnats, midges, blackflies
* horse flies, deer flies
* house flies, stable flies
* blue‐ and green‐bottle flies
* bot flies
* warbles
Diptera ‐ Life Cycle Strategies
Complex metamorphosis
Egg > Larva 1 > Larva n > Pupa > Adults
suborders of diptera
-Nematocera
-Brachycera
-Cyclorrhapha
Suborder Nematocera physical characteristics
*long, segmented antennae
*piercing‐sucking mouthparts
*females only blood‐feed
Suborder Brachycera physical characteristics
*stylate antennae
*slicing mouthparts, feed by telmophagy
*females only of most genera blood-feed
Suborder Cyclorrhapha physical characteristics
*aristate antennae
*variable mouthparts
Diptera ‐ Nematocera; what species in this suborder are we concerned about? how do they feed? why are they a problem?
*Mosquitoes, gnats, midges, blackflies
*females blood‐feed
*annoying ‐ causes “worry”
*may cause anemia
*may transmit pathogens
Diptera ‐ Brachycera; what species in thes suborder are we concerned about? how do they feed? why are they a problem?
*Horse flies and deer flies
*females blood‐feed
*painful bites
*loud fliers
* persistent
*annoying ‐ causes “worry”
Diptera ‐ Cyclorrhapha; what species in thes suborder are we concerned about?
*Various robust flies including house flies, stable flies, face flies, flesh flies, warble flies, and bot flies
*aristate antennae
*various mouthparts
Musca domestica
the uncommonly filthy house fly
Musca domestica physical characteristics
Musca domestica ‐ House Fly
*robust, hairy body
*aristate antennae
* sponging‐lapping mouthparts
*strong flier
Musca domestica ‐ House Fly; Life Cycle
- complex metamorphosis
- eggs laid in undisturbed cattle feces or other rotting organic matter (not too selective)
- maggots eat organic debris
- pupation in soil
- extremely prolific
Musca domestica ‐ House Fly; significance
*annoyance, nuisance
*efficient mechanical vector for pathogens
*feeding habits promote transmission
*biological vector of Habronema and Draschia of horses
Musca autumnalis ‐ Face Fly; physical characteristics
*morphologically similar to M. domestica (house fly)
* sponging‐lapping mouthparts
Musca autumnalis ‐ Face Fly; life cycle, feeding habits
*complex metamorphosis
*eggs laid in undisturbed cattle feces
*pupation in soil
*adults overwinter in buildings
*adults on horses and cattle outdoors only
*adults feed on eye, nose and mouth secretions
Musca autumnalis ‐ Face Fly; significance
*annoyance, irritation, worry
*mechanical vector for pathogens
e.g. infectious keratoconjunctivitis (Moraxella bovis)
*biological vector for eyeworms (Thelazia spp.)
Haematobia irritans
Horn Fly
Haematobia irritans ‐ Horn Fly; physical characteristics
*aristate antennae
*piercing‐sucking mouthparts
*about 1⁄2 of the size of a house fly
*almost constantly on hosts both inside and out
Haematobia irritans ‐ Horn Fly; life cycle
- eggs laid in undisturbed cattle feces
- maggots in feces
- pupation in soil
- pupae overwinter in soil
- adults on backs of cattle indoors or out
- adults pierce skin for blood
- adults leave cattle only to lay eggs
Haematobia irritans ‐ Horn Fly; significance
- annoyance, irritation, worry
- reduces milk production and weight gains
- significant blood loss in heavy infections
- biological vector for filarial nematode of cattle (Stephanofilaria stilesi)
Stomoxys calcitrans
Stable Fly
Stomoxys calcitrans ‐ Stable Fly; physical characteristics
*body similar to that of Musca spp. (often called a “biting house fly”)
*aristate antennae
* bayonet‐shaped mouthparts
(NOT ‐ sponging‐lapping mouthparts)
Stomoxys calcitrans ‐ Stable Fly; life cycle
*complex metamorphosis
*eggs laid in decaying vegetation
*maggots develop in damp straw, etc.
*pupation in soil ‐ overwinter as pupae
*adults attack mammals during midday
*adults pierce the skin for blood
*adults are persistent annoying pests
Stomoxys calcitrans ‐ Stable Fly; Significance
*painful bite
*persistent feeders that are easily disturbed
*therefore, annoyance and worry
*reduced milk production and weight gains
*significant pest of humans as well
*intermediate host for Habronema sp. (nematode of horses)
Biting and Non‐biting Muscid Flies Control Summary
1) Sanitation Measures
*timely removal of manure to reduce the number of breeding sites locally
*general cleanliness to remove sites with rotting vegetation (particularly wet decomposition)
*where feasible and desirable, ensure proper drainage to remove areas of standing water or muck
2) Insecticides
*ear tags impregnated with topical organophosphates or botanicals (e.g. rotenone, pyrethrins ) against face and horn flies
*spray‐on or pour‐on formulations of insecticides
*back rubbers may be useful on pasture
*chitin inhibitors in feed of cattle to make manure unsuitable for larval development
Melophagus ovinus
Sheep Keds
Sheep Keds – Melophagus ovinus; physical characteristics and life cycle
*Wingless fly
*Flattened dorso‐ventrally
*Leathery, hairy
*Complex metamorphosis
*Mature larvae laid by females spin cocoons immediately
Sheep Keds – Melophagus ovinus; significance
- Irritation
*Blood loss
*Wool damage through rubbing and staining
Sheep Keds – Melophagus ovinus; control
*Topical insecticides
*Usually a winter issue
Myiasis
*Invasion of healthy or damaged flesh by the larvae of dipteran flies
*both obligate (e.g. cattle grubs, Cuterebra, sheep nasal bots) and facultative myiasis (e.g. wool strike, blow flies)
*facultative myiasis generally start with a wound of some kind that attracts flies
Sarcophagids and Calliphorids; physical characteristics
*larger than a housefly
*brilliant metallic colouring (calliphorids) or grey checkerboard appearance (sarcophagids)
Sarcophagids and Calliphorids; larvae
Myiasis
*maggot, “screw‐worms”, up to 15 mm long
*typical, robust dipteran larva
Sarcophagids and Calliphorids; life cycle
*complex metamorphosis
*eggs usually laid in or around wounds, soiled
skin/wool, or in decaying carcasses
*species‐specific level of decomposition preferred
*larvae develop at or near site of oviposition
*mature larvae leave host to pupate
Sarcophagids and Calliphorids;
Predisposing causes for fly attack ‐ “wool strike”
*open wounds from any cause
‐ especially attracted to putrefying flesh
*decomposing wool on soiled/wet sheep
‐ may result from heavy rain, urine, uterine discharge, diarrhea, sweat, etc.
*locally, intestinal parasitoses resulting in diarrhea are a significant cause of wool decay and subsequent fly attack
Sarcophagids and Calliphorids; Pathogenesis
*maggots develop in wound or wool, feeding on dead tissues ‐ foul odour and brownish staining
*some may invade adjacent normal tissue
*decay of flesh may cause toxemia
*maggots may migrate under the skin for a significant distance and into underlying muscle
*sheep may kick or bite the “struck” area
Sarcophagids and Calliphorids; Treatment
*shear away wool from affected area
*physically remove all visible maggots, probing under flaps of skin to remove maggots and to debride decomposing flesh
*apply insecticides locally by spray or spread manually
*management of secondary bacterial infections may be necessary depending on severity of lesions
Bot Flies – Major Types and hosts
*Warble Fly (cattle grubs) – cattle, rarely horses
*Nasal Bot Fly (Oestrus ovis) ‐ sheep
*Rodent or Rabbit Bot Fly – small animals
*Stomach Bot Fly ‐ horses
Bot Flies – General Features
- Often large bee‐like adults – do not feed
- Large larvae must store energy for metamorphosis and egg‐laying
- Usually well‐prescribed sites of development
Hypoderma species; what are they? cause obligate what?
Hypoderma bovis
*Northern cattle grub
*Larvae overwinter in spinal canal or epidural fat
Hypoderma lineatum
*Southern or common cattle grub
*Larvae overwinter in esophageal connective tissue
Causes Obligate Myiasis
Hypoderma species; Life Cycle
*Complex life cycle
*Eggs laid on legs of cattle by non‐feeding adult flies
*Larvae penetrate skin – migrate to overwintering sites by December for about 3 months
* Late February through April – migrate to back
*Produce “warble” there – subcutaneous cyst
*Larvae mature, drop out of wound and pupate
* One cycle per year in Ontario
Hypoderma species; Pathogenesis/Lesions
- “gadding” results from oviposition – reduced production through energy expenditure
- holes in hides reduce value and lesions may require trimming in packing plant
- horse, loss of use if warble in saddle area
Cuterebra species; Morphology
*adults ‐ robust and bee‐like flies with vestigial mouthparts
*larvae ‐ large with prominent spines found within subcutaneous cysts of host
Cuterebra species; Life Cycle
*complex metamorphosis
*eggs found near burrow openings
*larvae enter host via nose or mouth
*migrates to skin and cuts breathing hole
*larva emerges from hole when mature
*pupation on ground (over‐wintering)
*adults mate and lay eggs the following year
Cuterebra species; Pathogenesis/Lesions/Clinical Signs
- subcutaneous fibrotic cyst
- wet coat in neck region
- small hole
- rarely, larvae enter the CNS
Cuterebra species; treatment
*surgical removal of the bot
*debride contents of cyst, if necessary
*local anti‐inflammatory/antibiotic
*systemic treatment if severe
Gasterophilus species
Stomach Bots
Gasterophilus intestinalis
* Most common >95%
Gasterophilus nasalis
* Uncommon locally
Gasterophilus species; life cycle
*Complex life cycle
*Most eggs on forelegs
(Gasterophilus intestinalis)
*Oral migration
*2nd stage larvae swallowed
*Larvae overwinter in stomach
*Larvae pass out with feces
Gasterophilus species; Pathogenesis/Lesions
- Usually asymptomatic but gastric lesion can be significant
*Rarely perforations can occur giving abscesses and peritonitis
Gasterophilus species; Control
- Many registered compounds available including insecticides and endectocides (macrocyclic lactones)
Causes Obligate Myiasis; which ones?
Gasterophilus species
Cuterebra species
Hypoderma species
=>all the bot flies
Anoplura
Sucking Lice
Anoplura ‐ Sucking Lice; general characteristics
*highly host‐specific
*feed on secretions, blood
*wingless, flattened (dorso‐ventrally)
head is narrower than the thorax
Anoplura ‐ Sucking Lice; life cycle, where are they found on the host
- simple metamorphosis
- eggs (nits) cemented to hairs or feathers
- life cycle about 2 ‐ 4 weeks
- entire life cycle on the host ‐ generally short survival off of the host
- sucking lice are usually found in groups attached to the host by their mouthparts ‐ often in protected areas
Mallophaga
Chewing or Biting Lice
Mallophaga ‐ Chewing or Biting Lice; General Characteristics, feeding habits
- highly host‐specific
- feed on skin, hair, secretions, feathers
- wingless, flattened (dorso‐ ventrally), head as broad as or broader than the thorax
Mallophaga ‐ Chewing or Biting Lice; Life Cycle
*simple metamorphosis
*eggs (nits) cemented to hairs or feathers
*life cycle about 2 ‐ 4 weeks
*entire life cycle on the host ‐ generally short survival off of the host
*chewing lice are usually active or highly active
Lice – Epidemiology; how do populations change over time, transmission
*Populations often increase in winter months
*Transmission is usually via direct contact but fomites can be involved
Lice – Control
*Many insecticidal products for control, spray, dips, dust bags, etc.
*Most kill only larvae and adults – re‐treatment is usually required
*May require vacating premises for short periods
