Lecture 6 - Insects: Diptera part 2

Question 1

Within the order of Diptera, there are the suborders ____, ____ and ____. The last of these, the ‘true flies’ can be distinguished primarily based on presence of ____ protruding from their antennae.

Answer 1

Within the order of Diptera, there are the suborders Nematocera, Brachycera and Cyclorrhapha. The last of these, the ‘true flies’ can be distinguished primarily based on presence of arista protruding from their antennae.

Question 2

List the four families within Cyclorrhapha and the ‘common’ name for their flies.

Answer 2

Oestridae (bot flies)

Muscidae (flies)

Hippoboscidae (louse flies)

Calliphoridae (blow flies)

Question 3

What are the three important genera of the family Oestridae we have learned about?

Answer 3

Gastrophilus

Oestris

Hypoderma

Question 4

What are the three species of Gastrophilus we have learned about? Which is least common?

Answer 4

G. intestinalis
G. nasalis
G. haemorrhoidalis (rare)

Question 5

Outline the basic life cycle of Gastrophilus spp.

Answer 5

Adult fly hatches in summer, has a few days to lay eggs
Lays eggs or live young at specific site on horse host
Larvae hatch (immediately, or when licked) and first instar migrates through oral cavity and gums to stomach
Larvae go through 3 instars in stomach or duodenum (depending on species) over the next 9 - 12 months

Are passed in faeces and pupate in soil

Question 6

What is the Family and Genus of this fly? How did you know?

Answer 6

Oestridae
Gastrophilus

> redundant mouthparts

> fuzzy, yellow, like a bumblebee

> long ovipositor

Question 7

Which image represents G. intestinalis larvae? What species does the other represent?

Answer 7

The top image

The bottom is G. nasalis

Question 8

Where in the stomach would you find G. nasalis larvae?

What about G. intestinalis?

Answer 8

Fundus and body - G. intestinalis

Duodenum - G. nasalis

Question 9

Which drugs (with an example of each) are effective against Gastrophilus spp? When is the best time of year to treat and why?

Answer 9

OP’s e.g trichlorphon
ML’s e.g ivermectin

Tx in winter because there are no female flies around, so won’t get immediate re-infection

Question 10

Name and briefly describe the life cycle of the nasal bot of sheep.

Answer 10

Oestris ovis

Live young laid by female fly on external nares of sheep host in summer

First instar migrates into nasal cavity where it undergoes two subsequent moults

Third instar sneezed out when becomes too large, and pupates in soil

Question 11

What are the three consequences of O. ovis infection in sheep?

Answer 11

Irritation

Chronic nasal discharge

Predisposition to pneumonia

Question 12

What feature does this image show prominently? Which parasite do they belong to?

Answer 12

Oral hooks of an Oestris ovis larval stage

Question 13

What are your treatment options for O. ovis?

Answer 13

OPs

MLs

Trematocides e.g closantel

Question 14

What are these organisms? How can you differentiate them?* What economically important disease are they responsible for?

Answer 14

Cattle warble flies Hypoderma bovis (left) and Hypoderma lineatum (right). Differentiate them body colour(?) - H. bovis is more grey. (check). Cause warbles in cattle.

Question 15

What are the two sub-families of the Family Muscidae we are interested in?

Answer 15

Muscinae and Stomoxinae

Question 16

What major morphological feature allows differentiation of Muscinae from Stomoxinae?

Answer 16

The mouthparts - Stomoxinae have long, sharp projection

Question 17

What are the two important species in the sub-family Muscinae we are concerned with? Which image here represents which one?

Answer 17

Musca domestica (left for each pair)

Musca vetustissima (right for each pair)

Question 18

What structures do the letters represent? What Family and sub-family does this fly belong to? How do you know?

Answer 18

A = antenna

B = Palpi

C = labium

D = labella

Muscidae; Muscinae = has stout mouthparts, looks like conventional fly

Question 19

What Family and Subfamily is this likely to be? How do you know?

Answer 19

Muscidae, Stomoxinae - looks like conventional fly + long, piercing mouthparts

Question 20

Name the ‘stable fly’ that feeds of horses’ blood. Is it host-specific?

Answer 20

Stomoxys calcitrans

Nope, both males and females will bite any mammal.

Question 21

Give the Order, Family, Sub-family and Species of this creature. Describe its life cycle briefly.

Answer 21

Order: Diptera
Family: Muscidae
Subfamily: Stomoxinae

Species: Haematobia exigua

Lays eggs in cow dung, larval stages in dung (4-5d), pupa in dung (5-7d), adults emerge and have 2h to find a host, need bloodmeal to breed, stay on host for most of time except to lay eggs.

Question 23

What diseases can Haematobia exigua transmit between cattle?

Answer 23

Trypanosoma evansi

Stephanofilaria spp.

Question 24

List four possible control mechanisms for Haematobia exigua

Answer 24

Any of:
Tunnel fly trap

Dung collection/beetles

Ear tags impregnated with insecticides (rotate OP and SP)

OP topical spray

Oral ivermectin that persists in dung

Question 25

What is the Order and Family of this creature?

Which wingless species in this family are we interested in?

Answer 25

Diptera, Hippoboscidae

Melophagus ovinus - the sheep ked

Question 27

You pull these parasites from the wool of some Merino sheep.

a) What Order, Family and Species are they?
b) What is the common name?
c) What other parasites do they need to be distinguished from?
d) Are they obligate?
e) What effects do they have on their host?

Answer 27

a) Order: Diptera, Family: Hippoboscidae, Species: Melophagus ovinus
b) Sheep ked
c) Need to differentiate from Phthiraptera (Anoplura and Mallophaga) - lice!
d) Yes - feed on blood exclusively
e) Cause anaemia, can transmit Trypanosoma