Since stingless bees lack stinging apparatus, their defense behaviors have been a topic of curiosity. Hence, this presentation focus on those defensive strategies and mechanisms used by stingless bees to protect themselves.
7.
Tetragonisca angustula
11 colonies
Predators
1 colony- Lestrimelitta limao/4 T. angustula
Live insects- Melipona, Trigona, asilid fly
Flight of T. angustula
I. Aerial defence
(Wittamann, 1985)
Ta
Ll
Ta
Ta
Ta
Ta
Ta
Ta
Ta
Ta
Ta
Ta
7
8. (Wittamann, 1985)
Nest entrance of T. angustula
The entrance tube
guarded by group of
hovering bees
The groups of > 40
workers.
The flanking flight
corridor to the nest
entrance from both
sides.
They rapidly attack
flying insect invaders
and force them to the
ground
Contd....
8
9.
1. Males waiting for females
They were workers (♀)
Flight behaviour
Males - zig zag
Hovers - right angle to nest entrance
Hypothesis on the hovering guards…
Contd....
(Wittamann, 1985)
2. Young workers at orientation flight
3. Defensive bees
9
10.
Hovering
Stable positions without
inspecting the surroundings of
the nest site
Nest entrance at 1cm slight
below the opening
Never observed facing in any
other direction
Stable at position even if hive
moved
Orientation flight
Characterized by wide loops
flown at rather low speed
after the bees had hovered
Facing the nest entrance at 30-
40 cm from it.
After about 3-4 min the bees
extended the range of loops
Finally flew away on foraging
trips
Contd....
2. Young workers at orientation flight
(Wittamann, 1985)
10
11.
3. Defensive bees
Dummy invaders passed in front of nest,
Darted towards the invader repeatedly
The bee attacked invaders vigorously.
Landed on it, trying to grasp the wings or legs with its mandibles.
L. limao stopped in the same way
emits citral from mandibular gland
Dead L. limao infront of nest with citral smell
• Hovering bees are defensive guards
• Aerial defense against flying predator
• Citral is a alarm kairomone
Contd....
(Wittamann, 1985)
11
12.
2 types of entrance guards
1. Hovering guards
Main groups & Side groups
Within 20cm of entrance
Faces flight path
2. Standing guards
20-25cm from entrance
To the right or left of entrance
II. Nest defence
(Gruter et al., 2011)
12
13. (Gruter et al., 2011)
Tetragonisca angustula
15 colonies
For 60 seconds
Every 2hr
8.00 – 20. 00 hours
3 days
Contd....
Number of standing & hovering guards
• Standing guards (14.3) = 2 Hovering guards (4.64)
• Standing - during day time & Hovering - intense during late afternoon
• No guarding after 8pm
13
14. (Gruter et al., 2011)
Will they close the door ????
Proportions of nest entrance tubes that are open at different
times of the day and night
Contd....
14
15. (Gruter et al., 2011)
Standing v/s hovering guard
• Max. guarding duration – 20 days
• Standing guard (91%)
• Hovering by sub-groups of guards (9%)
• 33% - both
Contd....
15
16. Low task switching between both
Standing guards hovering guards
Hovering guards- nest immunity against L. limao
allospecific defence
Standing guards- discriminate nestmate from conspecifics
conspecific defence
Long guarding duration of 20 days (LC- 21 days)--- guarding
is specialized task
Larger colony – more guards
The study concludes….
allospecific
intruder
(Gruter et al., 2011)
Contd....
16
17. Tetragonula carbonaria Smith
III. Fighting swarms
(Gloag et al., 2008)
10m radius
10workers/colony
DNA extraction
Kinship analysis- max. likelihood ratios
17
18.
1. Artificial introduction of worker
– at midday
2. Exchange of nests
-proxy of natural condition
To induce fighting swarm…
Control–
6 colonies
Source –
6 colonies
Receiver–
6 colonies
(Gloag et al., 2008)
Ho: Swarmrec. ǂ Swarmcntrl
Contd....
18
19.
Black - proportion of workers from the nest closest to the fighting
White & grey - % of workers from additional colony (identified in the collection)
N - Sample sizes for each fighting swarm collection ( given to right of each bar)
Number of colonies participating in 8 fighting swarm collections
(Gloag et al., 2008)
19
20.
(Cunningham et al., 2014)
Who wins the fight then ????
Bees at war !!!
• Tetragonula carbonaria v/s Tetragonula hockingsi
• 5 year period
• 260 stingless bee hive
20
21.
(Cunningham et al., 2014)
Behaviours observed during fights
Fighting bees on ground near the hive
Clusters of drones on nearby foliage
Attacking worker dragging a callow
21
23.
Callows ejected- 163
For 7 days
T. hockingsi ejecting
T. carbonaria
Callows ejected- 1389
For 2-4 days
All callows - T. carbonaria
takenover
(Cunningham et al., 2014)
Fighting pairs, ejected callow bees collected
outside focal T. carbonaria hive
Contd....
23
24. (Cunningham et al., 2014)
Changes in resident species of stingless bee hive
Year
Hive species
changes
% change
Tc to Th Th to Tc Tc Th X2
2008 10(253) 1(10) 4 10 ns
2009 8(268) 0(21) 3 0 ns
2010 9(252) 2(21) 4 10 ns
2011 8(253) 1(26) 3 4 ns
2012 6(274) 1(29) 2 3 ns
Total 41 5
Hive change occupancy of 46 colonies
Inter-colony battles in Tetragonula bees results in usurpation of
the defeated hive by the winning colony
Contd....
24
25. Secured nest entrance
Plant derived resins to form propolis
T. carbonaria ----> propolis + Corymbia tree resin
Entrance propolis : against Iridomyrmix mayri
Nonpolar solvent - hexane
Polar solvent - ethanol
IV. Chemical defence
Centre (brine)
Barrier ( treatment)
Outer
25
26.
(Wang et al., 2018)
• Nest entrance propolis deter ants
• Nonpolar, nonvolatile chemicals of propolis acts as deterrent
• Chemical composition varies wrt plant source
• Sesqui & di –terpenoids, phlorogilcinols, flavonoids
26
27.
Soldiers- rare in bees & absent in wasps
Worker differentiation in 28 stingless bee species
Captured workers
Measured size, Head weight[
𝐺𝑢𝑎𝑟𝑑𝑠 −𝐹𝑜𝑟𝑎𝑔𝑒𝑟
𝑆𝐷. 𝑜𝑓 𝑐𝑜𝑙𝑜𝑛𝑦
]
Quantified melanization, 𝑚 = 1 −
𝑔
r
• g- average grey scale of specimen
• r- reference grey scale
Cuticle thickness - TEM
V. Defense by soldiers
Gruter et al. (2017)
27
31.
Attack bioassay
(Shackleton et al., 2014)
Aggression =
𝑃𝑁𝐷
𝐿
P – probability of attack
N – number of attack
D – log10 attack duration
L – log10 latency
Suicidal bioassay: flag test - 20 m from the nest
brushed for 5 s using 5mm brush - no physical harm
wings clamped using forceps – physical damage
Choice btw
disengage/
self sacrifice
31
32.
(Shackleton et al., 2014)
All 3 species of Trigona- highly aggressive & suicidal
Most suicidal - Tr. hyalinata (83 %)
Contd....
32
34.
Conclusion
Fighting individuals - sterile workers benefits by indirect
fitness of protecting the colony
Improved defence - outweigh the costs of dead workers
Basic aerial defense to suicidal biting --- evolved defense
Meliponinae are stingless, not defenceless
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