Chemical signals and cues have been shown to play an outstanding role in intraspecific and interspecific communication systems within and outside of a bumble bee colony. In the present review we compile and critically assess the literature on the chemical ecology of bumble bees, including cuckoo bumble bees

2. Mogili Ramaiah
IARI, Ph.D Scholar
Division of Entomology
New Delhi-110012
Welcome
CHEMICAL ECOLOGY OF BUMBLE BEES
Credit seminar on
Good
Morn
ing

3. Introduction
Biology of Bumble bee
Social interaction
Foraging and Social parasitism
Case studies and Summary
Conclusions and Future prospects
CONTENTS

4. Bumble bees are of major importance, ecologically
and economically as pollinators
 Model organisms
Used to study ecological principles, social behavior,
foraging strategies, host-parasite interactions and
pollination
 Hydrocarbons, esters, alcohols, ketones, and fatty
acids
Introduction

5. The genus Bombus, the only one extant
genus in the tribe Bombini, comprises over
250 species
(Williams et al., 2008)
Taxonomy
Order: Hymenoptera
Family: Apidae
Eusocial: Highest level of organization of sociality,
Cooperative brood care (including care of offspring
from other individuals)
Overlapping generations within a colony of adults
A division of labor into reproductive and non-
reproductive groups

6. Martin et al., 2010
Nest building bumble bees
Sub-genus Species
Pyrobombus Bombus
lapidarius(Linnaeus)
B. jonellus (Kirby)
B. pratorum (Linnaeus)
B.monticola Smith
B. terrestris (Linnaeus)
B. lucorum (Linnaeus)
B. hortorum (Linnaeus)
B. pascuorum Scopoli
B. Muscorum (Linnaeus)
Bombus
Megabombus
Melanonombus
Thoracobombus

7. Parasitic bumble bees
Sub genus: Psithyrus
Martin et al., 2010
Species Host
B.(Ps.) bohemicus B. lucorum and B. jonellus (Kerby)
B.(Ps.) vestalis B. terrestris (Linnaeus)
B.(Ps.) campestris B. pascuorum Scopoli
B.(Ps.) rupestris B. lapidarius (Linnaeus)

8. Terminology
Cue: Information that is useful to the receiver but that has not been
shaped by natural selection
Signals: Structures or behaviors that have evolved to convey
information to other organisms
Odor trails: Chemical compounds deposited by bumble bee workers
between the nest entrance and the inner part of a nest; used by
cuckoo females to recognize host species
Switch point: Time in colony development at which the queen starts
to lay primarily haploid, (male); later, she again lays diploid eggs
Competition point: Colony phase in which workers show aggressive
behavior and start egg-laying, as well as egg-eating

9. Fertility signal: Signal advertising the presence and/or quality of
the queen; usually made of chemical compounds on the cuticle
surface
Primer pheromone: In social insects, usually a queen pheromone
that affects the physiology of receivers; in bumble bees, it
inhibits ovary development in workers
Electroantennogram: Electrophysiological recording of the
response of an insect’s peripheral sensing system, the antennae,
when stimulated with odor molecules
Gas chromatography coupled with electroantennographic
detection (GC-EAD): Method to separate single compounds in
a chemical blend and simultaneously test whether they are
detected by antennal chemoreceptors

11. Gurel et al., 2008
Summer
Spring
Autumn

12. Eggs
Worker
Fertile eggs
Unfertile eggs
Queen
Drones/males
Manfred and Stefen, 2014
Caste determination in Bumble bees

14.  The pheromone produced in the mandibular glands and spread over the
queen’s body surface by self-grooming.
 The mandibular gland’s secretion is composed mostly of a series of 3-
hydroxy acids accompanied by lesser amounts of alcohols, 2-ketones,
alkenes, alkanes, and fatty acyl esters.
 Queen pheromones delay ovarian development in young and old workers.
 Mouling: physical interaction.
Manfred and Stefen, 2014
Queen pheromones
Control of worker Reproduction

15. Fertility signals
 Fertility signals in bumble bees were found first in B. hypnorum
and more recently in B. terrestris.
Etya et al., 2014
WorkerQueen
wax-type esters
from cuticle

16. In bumble bees both mass provisioning and
progressive provisioning present
Pocket-makers
Ex.
B. pascuorum
B. hortorum
B. diversus
Pollen-storers
Ex.
B. terrestris
B. hypnorum
B. terricola
Den and Duchateau, 2006
Parental care in bumble bee?

17. A larval hunger signal in the bumblebee
Bombus terrestris
Den and Duchateau, 2006
Objective:
To investigate whether the larval cuticular chemicals could
function as a hunger signal.
Case study -1

18.  Ten similar sized normally fed larvae of about 5 days old
were collected
 Larvae were immediately washed in 1 ml n-pentane for 15
min
Extraction of larval cuticular chemicals
Starved larvae
extract
Normally fed
larvae extract
1 ml n-pentane
Den and Duchateau, 2006
A larval hunger signal in the bumble bee Bombus
terrestris

19. Den and Duchateau, 2006
Small broods
Colony with 30-40 workers
 Worker makes a small hole in it with her mandibles.
 The mandibles, antennae, and part of the head are
inserted and after a short period of immobility the
abdomen is lifted and a droplet of food is regurgitated
from the crop onto the larva’s ventral side.
Normally fed
larvae extract
Starved larvae
extract
N-pentane

20. 0.71
1.11
1.77
Den and Duchateau, 2006
Mean number of feedings per larva per hour for the three different
treatments

21. FORAGING

23.  Foraging bumble bees deposit an organic
substance (cuticular materials) on rewarding
flowers by grooming.
Sydney, 1981
How bumble bee differentiate rewarding non
rewarding flower ?

24. Chemical Signals in Bumble Bee Foraging
Sydney, 1981
Bumble bee hive
Case study -2

25. Rewarding (Rwd=98.0±1.1%)
Previously rewarding (N’=54.6±
15.5%)
Previously Rwd flower washed in
water (N‘H2O = 28.8 % ± 14.6%)
Previously rewarding washed in
ethyl alcohol (N‘Alc= 15.5- ± 4.8%)
Previously rewarding washed in
pentane (N'pe.~ =4.1 ± 2.8%)
Frequency of probing by bumble bees on differently treated
flowers
Sydney, 1981

26. Footprints
Bumblebees sense nesting material
Rottler et al., 2013
How bumble bee recognise their nest.... ?

28. Bumble bee Cuckoo bumble bee

30. How cuckoo bumble bee search it’s host nest…

31. Objectives:
 Identifying the foot-print compounds of the host species
 Whether the generalist cuckoo bumblebee B.
bohemicus and the specialist B.vestalis use the same
or different substances to recognize their common
host.
Kreuter et al., 2010
Specialist Bombus vestalis & generalist B. bohemicus use different
odour cues to find their host B. terrestris
Case study -3

34. Kreuter et al., 2010

35. Bombus vestalis Bombus bohemicus
Kreuter et al., 2010

36. What are strategies used by cuckoo bumble
bee to invade the host colony

37. Bombus/Psithyrus sylvestris,
(Forest cuckoo bumblebee)
Bombus/Psithyrus bohemicus,
Gypsy cuckoo bumblebee
Bombus/Psithyrus vestalis,
(Southern cuckoo bumblebee)
Bombus terrestris
Bombus lucorum
Bombus pratorum Bombus jonellus

38. Martin et al., 2010
Chemical mimicry
Repellent produced by cuckoo bumble bee – dodecyl acetate
Host Specific Social Parasites (Psithyrus) Indicate Chemical
Recognition System in Bumblebees
Case study -4

41. -- Alkanes
-- dodecyl acetate
-- Alkenes
0.00E+00
a- cuticular hydrocarbon extracted from the wing
b- cuticular hydrocarbon extracted from the Dufour's gland
Martin et al., 2010

42. Zimma et al.,2003
 Do the substances that are electro-physiologically active
have a repellent effect on host workers?
Australia
Do social parasitic bumble bees use chemical
weapons ????????
Case study -5

43. Bombus norvegicus
B. hypnorum

46. Sugar water
 Pentane
 GC –EAD
blend
 Dodecyl
acetate
 Citral
 Farnesol

47. Zimma et al.,2003

48. Zimma et al., 2003

49. Conquest of cuckoo bumble bee over
Bumble bee

50. Sramkova et al ., 2009
Chemical ecology involved in invasion success of the cuckoo
bumblebee Bombus vestalis and in survival of workers of its
host Bombus terrestris
Case study -6

51. How do cuckoo bumble bee male offspring's escape
from host aggression?

52. Patrick et al., 2012
 Parasite males completely lack the morphological and chemical
adaptations to social parasitism that the females possess.
 Young cuckoo bumblebee males produces repellent odor that
prevents parasite males from being attacked by host workers.

53. Summary
1. Bumble bees are model organisms to study aspects of
regulation of reproduction. In B. terrestris the occurrence
of a queen primer pheromone has been verified, but the
chemicals involved have not been identified.
2. Cuckoo bumble bees evolved remarkable strategies to find
and invade host colonies and to manipulate host worker
behavior. Chemical ecology plays a key role in these
interactions.
3. After invasion of a host colony, female parasites adjust to
the odor profiles of their host queens to maintain the level
of fertility signaling, there by manipulating worker
behavior.

54. 4. Foraging bumble bees distinguish between unvisited and
visited (i.e., depleted) flowers by using hydrocarbon cues left
behind by previous visitors and thus avoid landing on depleted
flowers; the interpretation of the cues by foragers requires
context-dependent learning.
5. Bumble bee foragers can animate nestmate workers to leave
the colony, supposedly for the purpose of food collection, by
means of physical contact and by a pheromone emanating from
dorsal abdominal glands.

56. We are still far away from fully understanding chemical
communication in bumble bees such as male pheromones and
queen pheromones
We know much more about the chemical structures of compounds
that are likely involved in communication than about how these
compounds act.
Learning experiments are needed with respect to host searching
behavior of cuckoo bumble bee.
Diagnostic bioassays are needed to identify behaviorally active
compounds in complex secretions of male bumble bees
Conclusion

57. Future Prospects