Scent Mimicry... the story of the beewolf and the cuckoo wasp

The European beewolf (Philanthus triangulum) hunts worker honey bees (Apis mellifera) almost exclusively as a food source for offspring (Strohm et al, 2008). The female beewolf paralyses the worker bee and stores several of them in an underground nest chamber up to 1m long (Strohm et al, 2008). The beewolf then closes up the nest entrance and creates a side entrance where she enters and creates a chamber for brood where she will store 1-6 of the paralysed bees – on one she will deposit an egg (Strohm et al, 2008). The female beewolf even licks the bees, depositing a secretion from the postpharyngeal glands that prevents fungal growth on the bee before the egg can hatch, ensuring there are provisions for her young (Herzner et al, 2007). The beewolf then closes up the brood chamber carefully and never has any contact with her offspring, but she makes sure to leave the kids a packed lunch (Strohm et al, 2008).

European beewolf (Philanthus triangulum) and paralysed worker  honey bee (Apis mellifera)

The female beewolf leaves little opportunity for her vulnerable young to be predated on as she waits until after she has collected food before depositing an egg, then immediately closes the chamber (Strohm et al, 2008). The biggest threat to the beewolf is brood parasitism, and it is believed the beewolf has adopted behaviours to avoid hunting when the parasite species is most active known as an ‘enemy-free space strategy’ (Polidori et al, 2010).

cuckoo wasp (Hedychrum rutilans) approaches beewolf (Philanthus triangulum) nest

There is a specialised cuckoo wasp (Hedychrum rutilans) that has adapted to parasitise the beewolf by depositing an egg in with the beewolf offspring and provisions, that egg hatches and the larvae eats both the paralysed bees and the beewolf offspring. It is believed the cuckoo wasp adopts a combination of strategies to prevent being detected by the beewolf. The cuckoo wasp remains motionless or runs away when they run into the beewolf in her nest and the cuckoo wasp doesn’t leave much evidence of their deception (Strohm et al, 2008). The most interesting strategy though is that the cuckoo wasp avoids detection when they are confronted by a beewolf inside her nest by producing scents very similar to that of the beewolf and leaves inconspicuous scent marks when they deposit an egg into the paralysed bee – this is believed to be the first known chemical mimicry in a parasite of a solitary wasp (Strohm et al, 2008).

Below is a video showing an interaction between the small parasitic cuckoo wasp and the much larger beewolf.

References:

Strohm,E, Kroiss, J, Herzner,G, Laurien-Kehnen, C, Boland, W, Schreier, P & Schmitt, T 2008, ‘A cuckoo in wolves' clothing? chemical mimicry in a specialized cuckoo wasp of the European beewolf (Hymenoptera, Chrysididae and Crabronidae)’, Frontiers in Zoology, vol. 5.

Herzner, G, Schmitt, T, Peschke, K, Hilpert, A & Strohm, E 2007, ‘Food wrapping with the postpharyngeal gland secretion by females of the European beewolf Philanthus triangulum’, Journal of Chemical Ecology, vol. 33, pp. 849–859.

Polidori, C, Bevacqua, S & Andrietti, F 2010, ‘Do digger wasps time their provisioning activity to avoid cuckoo wasps (Hymenoptera: Crabronidae and Chrysididae)?’, Acta Ethol, vol. 13, pp. 11-21.

Image 1: Schmidt, Y 2005, Sphecidae of Europe - Hymenoptera Information System, viewed 28 May 2015, <http://uae.hymis.eu/images001/337_Philanthus_triangulum_Juergen_Schmidt_600x400.jpg>

Image 2: Naturalis Historia 2011, Naturalis Historia, viewed 28 May 2015, <http://www.naturalis-historia.de/bilder/Hedychrum%20rutilans%20f10.JPG>

Video: Bee Wolf Wasp v.s. Cuckoo Wasp - slow motion test Corel Video Studio x5 2012, youtube, viewed 28 May 2015, <https://www.youtube.com/watch?v=M3ApIC9B5I4>

Coevolution in Hymenoptera... the Honey Bee vs. the Giant Hornet

Just about everyone is aware of honey bees (Apis sp.); the crop pollinators, covered in fur and ever so adorable. Less people will know about the Giant Hornet (Vespa mandarinia japonica) that is found throughout Asia and a fierce hunter of the honey bees being able to decimate an entire hive on European honey bees (Apis mellifera) in only a couple of hours. They have a body size of 4-5cm, can travel at speeds of 40km/hr and has a stinger over 0.5cm that injects potentially lethal venom and leaves a wound similar to a bullet hole – it is responsible for over 40 deaths a year in Japan alone. Both species are social and although a vast size and weaponry difference, the native Asian honey bees (Apis cerana japonica) have adapted to this predation in a very interesting way.

Japanese Giant Hornet (Vespa mandarinia japonica) compared to a honey bee (Apis sp.)

V. mandarinia japonica is the only hornet species that have evolved mass predation on other social hymenoptera (Ono et al, 1995). A solo scout hornet will find a food source (for e.g. a honey bee colony) and will kill individual bees to take back to their nest, after several individual kills are made the scout hornet will mark the site with a secretion of a forging site marking pheromone, other foraging nest mates will detect the pheromone and begin killing individual bees as well (Ono et al, 1995). Then things get a little brutal: once there are three or more individual hunting hornets on one hive the hornets attack as one, with each hornet being able to kill 40 bees in a minute with its mandibles - 10-20 hornets can kill over 30,000 bees in one massacre lasting less than 3 hours (Ono et al, 1995).

V. mandarinia japonica attacking an A. mellifera hive and the pile of bodies left from the massacre.

However, the slaughter is what is expected (and seen) when the hornets encounter the introduced European honeybee (A. mellifera). It has been shown that the Japanese Asian honey bee (A. cerana japonica) is able to defend its hive from a mass attack (Ono et al, 1995). A. cerana japonica can detect the hornets pheromone and lure the first scout hornet into the hive by teasing it from the entrance with 100 tasty worker bees who vibrate their abdomens for further temptation - little does the hornet know, there are a thousand bees that have dropped their hive duties and descended from the honeycomb to lie in wait just inside the hive opening (Ono et al, 1995).  As soon as the hornet attacks a bee inside the hive it is engulfed in a ball (‘hot defensive bee ball formation’) of bees that vibrate their bodies, producing high temperatures (47˚C) in the centre of the ball (Ono et al, 1995). But it is not just the temperature that kills the hornet, oh no it gets better – the bees also produce lethal amounts of Carbon dioxide (CO₂) inside the ball that in combination with the high temperatures kills the hornet within 10 minutes (Sugahara & Sakamoto, 2009). It has been found that mixed-species colonies of A. cerana and A. mellifera are able to form this death ball but not as effectively as a pure A. cerana colony (Tan et al, 2011).

A. cerana japonica in the hot defence bee ball formation around v. mandarinia japonica

It is not known as yet exactly how the A. cerana japonica form the defensive ball so quickly as there is some evidence of both acoustic and chemical communication (Ono et al, 1995). It is believed that the V. mandarinia japonica evolved their mass attack as a coevolutionary strategy to counteract the A. cerana japonica defence tactic – the mass attack often works when the bee colony numbers are low, the hornet can then take over the bee’s home and can provide large amounts of food for reproductives (Ono et al, 1995).

References:

Ono, M, Igarashi, T, Ohno, E & Sasaki, K 1995, ‘Unusual thermal defence by a honeybee against mass attack by hornets’, Nature, vol. 377, pp. 334-336.

Sugahara, M & Sakamoto, F 2009,’ Heat and carbon dioxide generated by honeybees jointly act to kill hornets’, Naturwissenschaften, vol. 96, pp. 1133–1136.

Tan, K, Yang, M, Wang, Z, Li, H, Zhang, Z, Radloff, SE, Hepburn, R 2011, ‘Cooperative wasp-killing by mixed-species colonies of honeybees, Apis cerana and Apis mellifera’, Apidologie, vol. 43, pp. 195–200.

Image 1: Armstrong, WP 2012, Wayne's Word, viewed 25 May 2015, <http://waynesword.palomar.edu/images2/AsianHornet5c.jpg>

Image 2: unknown contributor (Korean site – etorrent.co.kr), viewed 25 May 2015, <http://cdn9.pikicast.com/card/3d9b7f26-f956-4a5f-9180-8613b4b4f880_20150330173643989.jpg>

Image 3: Hypescience 2014, Hypescience, viewed 25 May 2015, <http://hypescience.com/wp-content/uploads/2014/10/abelhas.jpg>

Australian native bees – a possible ‘plan b’ for crop pollination in Australia?

As mentioned in a previous blog, the worlds honey bee (Apis mellifera) population is under threat from disease, parasites and the fatal phenomena known as Colony Collapse Disorder. Many of the most severe issues (CCD and Varroa mite most notably) have not reached Australia - but thankfully we have a large array of native bees that could become literal life savers to the human population should those problems arise.

Rescued Tetragonula sp. colony that was transferred into a wooden hive. Notice the difference in honey storage - stingless bees store honey in 'pots' and Apis sp. store honey in cells.

Australia has about 10 species of stingless bees (from the genera Tetragonula and Austroplebeia) which are reported to be important crop pollinators of macadamia, mango, lychee and watermelon and may benefit strawberry, citrus, avocado and more (Australian Native Bee Research Centre, 2014). There are many traits that stingless bees possess that would make them comparable to A. mellifera, including the following:

• Polylectic and adaptable – they will visit a variety of plants and will adapt to new species
• domestication – some species can be kept in hives and managed
• perennial colonies – year round foraging
• constancy – workers visit one plant species per trip
• forager recruitment – like the bees recruitment dance, workers provide information to others on location of food sources
• storage of food – their need to continuously stock-up on food despite adequate stores can be mutually beneficial to crops and the bee
• resistant to diseases and parasites that kill A. mellifera

(Heard, 1999).

There is research being done into the effectiveness of Tetragonula carbonaria on pollinating capsicum species in greenhouses and they have been found to be very effective pollinators in confined spaces such as glasshouses (Australian Native Bee Research Centre, 2014).

Tetragonula worker shows her adaptability by stealing some free wax from a candle. image courtesy of Peter O. 

Certain crops require buzz-pollination, or sonication pollen-dispensing, which requires a bee to vibrate its wings at a certain frequency while on a flower allowing it to shed its pollen (Moore, 1996). Research has been done on the use of native Blue Banded bee species Amegilla chlorocyanea in buzz pollination of tomatoes in greenhouses and the findings show that they are very effective visiting up to 1200 tomato flowers per day (Hogendoorn et al, 2007). The video below lets you see and hear the process of Amegilla sp. buzz pollinating a backyard tomato plant.

There are multiple native bee species - including Carpenter (Xylocopa sp.), Blue Banded (Amegillia sp.), Teddy Bear (Amegilla (Asaropoda)) - capable of performing this task and so prevent the need to introduce European bumblebees (Bombus terrestris) to mainland Australia (Australian Native Bee Research Centre, 2014).

Great Carpenter Bee (Xylocopa sp.) buzz pollinating a flower. photo courtesy of Corinne Jordan and the Australian Muse. 

References:

Heard, TA 1999, ‘The role of stingless bees in crop pollination’, Annual Review of Entomology, vol. 44, pp. 183-206.

Hogendoorn, K, Coventry, S & Keller, M 2007, 'Foraging behaviour of a blue banded bee, Amegilla chlorocyanea in greenhouses: implications for use as tomato pollinators’, Apidologie, vol. 38, pp. 86-92.

Moore, PD 1996, ‘The buzz about pollination’, Nature, vol. 384, pp. 27.

Aussie Bee, Australian Native Bee Research Centre, North Richmond NSW, viewed 10 May 2015, <http://www.aussiebee.com.au/croppollination.html>

Image 1: ABC Science, Australian Broadcasting Corporation, Ultimo NSW, viewed 10 May 2015, <http://www.abc.net.au/science/scribblygum/may2003/img/hive.jpg>

Image 2: New stingless bee photos by Peter O, Australian Native Bee Research Centre, viewed 10 May 2015, <http://www.aussiebee.com.au/Images/stingless-bee-petero-1.jpg>

Image 3: Great Carpenter Bee sonication - Corinne Jordan, Australian Museum, Sydney, viewed 10 May 2015, <http://australianmuseum.net.au/Uploads/Images/23048/Winner%20open%20215_big.jpg>

Video 1: ‘Australian Blue banded bee. (Amegilla cingulata)’, Youtube, viewed 10 May 2015, <https://www.youtube.com/watch?v=7h0Hm4E6CRk>

Myrmecomorphy: I wish I wish I was an ant... mimicry of ants

Ants; ferocious and efficient predators that can overwhelm prey much larger than themselves through tactical attacks, strong mandibles, a sting or the ability to spray formic acid on their target and the force of sheer numbers. It is no surprise then that ants have had significant impacts on the evolution of other organisms through symbiotic relationships, providing resources and being the subject of mimicry (McIver, 1993). Myrmecomorphy is the term for species that resemble ants morphologically, behavioural, chemically or texturally (McIver, 1993). Over 2000 species of myrmecomorphic arthropods from 54 families have been described so far including spiders, Leaf bugs (Miridae), broad-headed bugs (Alydidae), mantises (Mantidae), and even other Hymenopterans including parasitic wasp species from the Diapriidae family (McIver, 1993).

Parasitic wasp (Bruesopria sp.) inside the nest of its host species, the thief ant (Solenopsis molesta). Young wasps likely feed on the developing ant larvae. Image taken in Kansas, USA courtesy of Alex Wild.

Myrmecomorphic spiders have developed some of the most amazing morphological traits in order to mimic ants considering they are not even in the same taxonomic class. Some species of ant mimic spiders use their extra pair of legs as fake antenna, the cephalothorax has narrowed in the centre used to give the illusion of 3 body segments, some species have enlarged pedipalps/chelicerae used to mimic the ants head, reflective hairs to appear shiny or smooth textured and colour spots to mimic compound eyes are just some of the adaptions made (McIver, 1993).

Aphantochilus rogersi (left) captures a turtle ant (Cephalotes sp.). Image taken in Ecuador courtesy of Alex Wild.

Spiders don’t just use this mimicry in order to prey on the ants, some use batesian mimicry to avoid being eaten themselves. Here in Australia we have an amazing little Green Weaver Ant (Oecophylla smaragdina) mimic - Myrmarachne smaragdina – this species has adopted both morphological and behavioural features of the ants in order to avoid predation and lives near colonies of O. smaragdina without being attacked (Ceccarelli, 2008).

Female Myrmarachne smaragdina – Green weaver ant mimic spider. Photo taken in Darwin courtesy of Dr Greg Anderson.

Male Myrmarachne smaragdina – Green weaver ant mimic spider. Photo taken in Cairns courtesy of Robert Whyte.

References:

McIver, JD 1993, ‘Myrmecomorphy: morphological and behavioural mimicry of ants’, Annual Review of Entomology, vol. 38, pp. 351-379.

Ceccarelli, FS 2008, ‘Behavioral mimicry in Myrmarachne species (Araneae, Salticidae) from North Queensland, Australia’, Journal of Arachnology, vol. 36, no. 2, pp. 344-351.

Image 1: Ant Enemies, Alex Wild: The diversity of insects, viewed 9 May 2015, 2015, <http://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Solenopsis/i-RZcnVdD/1/L/Diapriidae4-L.jpg>  

Image 2: Amazing Arachnids, Alex Wild: The diversity of insects, viewed 9 May 2015, <http://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Cephalotes/i-6WhGGgx/2/XL/Aphantochilus3-XL.jpg>

Image 3 (female): Whyte, R & Anderson, G 2010, Salticidae Jumping spiders, Queensland Museum, viewed 9 May 2015, <http://www.arachne.org.au/_dbase_upl/smaragIMG_0342-resized.jpg>

Image 4 (male): Whyte, R & Anderson, G 2010, Salticidae Jumping spiders, Queensland Museum, viewed 9 May 2015, <http://www.arachne.org.au/_dbase_upl/P1000959Iain__29_Dec_11_Myrm.jpg> 

Symphyta: the First Hymenoptera

So far I have mainly discussed the social insects in the suborder Apocrita (wasps, ants and bees) from which most of Hymenoptera belong to. But there is another suborder of the Hymenoptera – the Symphyta - which contains the sawflies, horntails and parasitic wood wasps. 

Image 1: Paperbark or Melaleuca Sawfly (Lophyrotoma zonalis)

The Symphyta are believed to be the most primitive of the order based on their morphology and being that they are the first hymenopterans found in fossils – the earliest being Xyelidae found in Middle Triassic fossil records from Central Asia (Wang et al, 2014). The Xyelidae are considered to be the basal group from which all other hymenopterans evolved and some of the members of this superfamily have primitive features that have been abandoned by other hymenoptera (Gauld & Bolton, 1988). 

Image 2: Dorsal view of Sawfly (Cathayxyela extensa sp.) fossil found in China (Wang et al, 2014). 

One of the distinctions between Symphyta and Apocrita is the ovipositor – on Symphyta it is saw-like (hence the name sawflies) which allows the female to make slits or borings in the host plant in which to lay her eggs (Gauld & Bolton, 1988). Morphologically the Symphyta also lack the tapered typical wasp-waist and a stinger as seen on the Apocrita and hold their wings flat over the body (The University of Edinburgh, 2001). Although not social, there is evidence of group pupation and some mother Symphyta will provide defence to young and will viciously attack predators (Costa, 2007). 

Image 3: Sawfly (Perga sp.) mother defends her offspring, photo courtesy of Kristi Ellingsen. 

The larvae of Symphyta feed on host plants completely exposed, in leaf rolls/webs or concealed within parts of the plant such as the fruit; however there are some species (from the Orussidae superfamily) that are parasitic (Gauld & Bolton, 1988). Adult sawflies feed from flowers, on parts of the flower and some species are carnivorous (Gauld & Bolton, 1988). The majority of Symphyta larva are caterpillar-like but have at least six pairs of prolegs compared to the caterpillars maximum of five and lack the hooks that caterpillars have on their prolegs (Barnard, 2011). 

Having a similar life to the caterpillar, Symphyta larvae are subject to similar selective pressures as butterfly larva and they have developed similar chemical and communicative defence mechanisms (Costa, 2007). Communication has been observed in Australian species Perga affinis and Perga dorsalis in the form of substrate borne vibrational cues made by a hardened cover on the tip of the abdomen being tapped on surfaces to signal group members to reunite (Costa, 2007). The North American red-headed pine sawfly, Neodiprion lecontei, has been found to use chemical cues to communicate with other members of the group (Costa, 2007). Below is a video showing the “tapping” communication in a Perga sp. in Australia.

The best example of chemical defence in the Symphyta larvae comes from the Australian Steel-blue sawflies (Perga sp.) found around South Eastern Australia - they are commonly known as ‘spit-fires’ as they eject an irritating fluid from their mouths as a defence against predation (Australian Museum, 2015). Below is a video showing the defensive behaviour of spit-fires.

References:

Barnard, P 2011, Royal Entomological Society Book of British Insects, Wiley-Blackwell, Hoboken NJ. pp. 226-267.

Costa, JT 2007, Social Sawflies, Department of Biology Western Carolina University, viewed 19 April 2015, <http://web.cortland.edu/fitzgerald/sawflies.html>

Gould, I & Bolton, B 1988, The hymenoptera, Oxford University Press, Oxford.

Wang, M, Rasnitsyn, AP & Ren, D 2014, ‘Two new fossil sawflies (Hymenoptera, Xyelidae, Xyelinae) from the Middle Jurassic of China’, Acta Geologica Sinica (English Edition), vol. 88, no. 4, pp. 1027-1033.

Steel-blue sawflies, Australian Museum, viewed 19 April 2015, <http://australianmuseum.net.au/steel-blue-sawflies>

Image 1: Melaleuca Sawfly (Lophyrotoma zonalis), viewed 19 April 2015, <http://www.ozanimals.com/image/albums/australia/Insect/Melaleuca-sawfly-1.jpg>

Image 2: Wang, M, Rasnitsyn, AP & Ren, D 2014, ‘Two new fossil sawflies (Hymenoptera, Xyelidae, Xyelinae) from the Middle Jurassic of China’, Acta Geologica Sinica (English Edition), vol. 88, no. 4, pp. 1027-1033.

Image 3: Only a mother could love them - Kristi Ellingsen, Australian Museum, viewed 19 April 2015, <http://australianmuseum.net.au/Uploads/Images/10229/OP105_Only%20a%20mother%20could%20l.jpg>

Video 1: Spitfires, youtube, viewed 19 April 2015 <https://www.youtube.com/watch?v=oNos7PDWjkg>

Video 2: Sawflies and spitfire grubs, youtube, viewed 19 April 2015 <https://www.youtube.com/watch?v=MB_oapTpIQk> 

Asian Honey Bee's and the threat to Australia

In 2007 the first colony of Asian Honey Bee or AHB (Apis cerana javana) was detected in Cairns, Queensland. There were attempts to eradicate this species, but in 2011 all attempts were declared unsuccessful and containment programs have since begun to control the spread of A. cerana (Australian Department of Environment, 2011).

If the world is currently facing a bee crisis of sorts; with Colony Collapse Disorder becoming a serious threat to Apis mellifera colonies throughout the globe, why are we so concerned about another species of bee becoming established here in Australia? Apart from the safety aspect (as many colonies are found close to human habitats), we will look at the other major issues with invasive bees.

Apis cerana javana swarm inside a letterbox in Cairns, Queensland.

We have had introduced European honey bee (A. mellifera) in Australia for 190 years and Bumble bees (Bombus terrestris) in Tasmania since 1992 – both species have created food and habitat competition to native species, with the B. terrestris competition creating displacement of 2 native bee species (Australian Department of Environment, 2011). It has also been found that Bumble bees pollinate invasive species so effectively they increase the seed viability of some of these invasive plants (Australian Department of Environment, 2011). AHB’s are an incredibly versatile species and are able to act as part of a colony (eusocial) and as a solitary individual as well as foraging from many minor sources of food (native and introduced species) rather than one crop – this contributes to the AHB’s highly successful ability to invade a region (Australian Department of Environment, 2011). So the AHB has the ability to be flexible in a range of environments, out-compete native species and contribute to the spread of invasive plants.

Apis mellifera & Bombus terrestris foraging on the same flowers

A. mellifera are established crop pollinators in Australia and are vital to the agricultural industry and food production. In 2008 it was estimated that the pollination services and the production of bee products in Australia was worth between $4 and $6 billion (Australian Department of Environment, 2011). The threat posed to A. mellifera by AHB’s (apart from competition) is that they are a natural host to the mites Varroa destructor and Varroa jacobsoni which are parasitic mites that feed on the larvae of the bee - these are non-natural parasites to A. mellifera (Australian Department of Agriculture, 2015).

Reproductive Varroa mite on a developing pupa (reddish oval) and two immature Varroa (opaque ovals). Credit: Abdullah Ibrahim (arrows added for emphasis)

It is believed that AHB’s have grooming behaviours that A. mellifera do not display and are therefore less likely to remove the parasites from brood (Carr, 2011). Varroa mites are responsible for the destruction and collapse of A. mellifera hives wherever it is present around the world – thankfully it is yet to be recorded in Australia but if it does arrive on our shores it will spread rapidly and is therefore considered the greatest threat to the honey bee industry (Queensland Department of Agriculture and Fisheries, 2015).

Here is a video showing ways that AHB colonies are destroyed here in Australia by Biosecurity Queensland – please do not try to remove colonies yourself, call a professional - these bees can sting, are venomous and will defend themselves if they are threatened.

References:

Invasive Bees, Australian Department of Environment, viewed 12 April 2015, <http://www.environment.gov.au/biodiversity/invasive-species/insects-and-other-invertebrates/invasive-bees>

The Asian Honey Bee in Australia, Australian Department of Agriculture, viewed 12 April 2015, <http://www.agriculture.gov.au/pests-diseases-weeds/bees/the-asian-honey-bee-in-australia>

Carr, AJ 2011, Asian honeybee: possible environmental impacts, Department  of  Sustainability, Environment, Water, Population and Communities,  Sustineo Pty Ltd, Canberra. 

Varroa mites, Queensland Department of Agriculture and Fisheries, viewed 12 April 2015, <https://www.daf.qld.gov.au/animal-industries/bees/diseases-and-pests/asian-honey-bees/general-information-on-varroa-mites>

Image 1 – Asian honey bee (Apis cerana) colony in mailbox, Queensland Department of Agriculture and Fisheries, viewed 12 April 2015, <https://www.daf.qld.gov.au/__data/assets/image/0004/53428/ahb-nest-letterbox.jpg>

Image 2 - Honey Bee Viruses: the Deadly Varroa Mite Associates, extension.org, viewed 12 April 2015, <https://www.extension.org/sites/default/files/pupavarroa.jpg>

Video 1 - Apis mellifera & Bombus terrestris - Sedum 'Matrona', youtube, viewed 12 April 2015 <https://www.youtube.com/watch?v=WiHP17AbQU4>

Video 2 - Asian honey bee destruction techniques for industry use by Biosecurity Queensland, youtube, viewed 12 April 2015 <https://www.youtube.com/watch?v=afrOmz7qXCk>

Mechanisms behind eusocial societies in hymenoptera - part 2

In the last blog, I discussed one of the driving mechanisms behind the evolution of socialism in hymenoptera – kin selection. In this entry I will look at another major driving force of socialism – maternal (or parental) manipulation.

Queens manipulate their offspring via genetic, physiological and behavioural avenues to ensure they remain within the colony to assist with raising their siblings (Gauld & Bolton, 1988). By doing this individuals forfeit their own breeding potential, form worker castes & enhance the queens reproduction potential (Gauld & Bolton, 1988). Much like the kin selection theory – the maternal manipulation theory requires prolonged mother-daughter relationships and overlapping generations (Gauld & Bolton, 1988).

Image 1 - Yellowjacket (Vespula spp.) queen, gyne, and males. 

In order for mothers to be able to manipulate their offspring without driving them away from the colony, the mother needs to move from basic parental care (such as that in pre-social wasps) into controlling the early development of her daughters so they will remain in the colony and assist in brood care (Brian, 1983). This manipulation may be driven by multiple factors including:

• Sex control that ensures a sterile worker caste and an exclusion of males until required (also derived from haplodiploidy)
• Moothers producing more offspring than required – a method which requires large numbers of substandard offspring to develop into a sterile worker caste through domestication – but this does not ensure that females will not leave the colony to create their own. This would require further manipulation through the development of a kin-help allele.
• The establishment of a gene which creates a sensitive phase during early development that can imprint a caste on the individual.

(Brian, 1983)

Image 2 - Red fire ant (Solenopsis invicta) castes and developmental stages.  Worker, male, and queen (top to bottom) adult, pupa, and larva (left to right).

Dawkins (1976) argues that even though the Queen has unchallenged control over her juvenile offspring, there must be some genetic symmetry otherwise the lack of any gain to the worker would allow cheat or non-cooperation genes to spread in offspring (Brian, 1983).

Two other theories have been hypothesised - one being polygyne families where many queens copulate but only the fittest queens are socially selected to produce brood and the least fit individuals are excluded after their brood is found to be inferior (Brian, 1983). 

Image 3 - Multiple queens in a colony of big-headed ants (Pheidole megacephala) in St. Lucia, South Africa. Image courtesy of Alex Wild.

The other is group selection where a population is split into sections (demes) that only come into genetic contact with each other briefly and rarely (Brian, 1983). Within the small population of the demes there is interbreeding which allows for random drift in allele frequency – this may lead to demes with unfavourable alleles dying off and demes with favourable alleles surviving (Brian, 1983). While these alleles may benefit a group they may be a disadvantage for the individual (e.g. sterility) however it has been found that the survival of a group is a direct function of the proportion of kin-help alleles (Brian, 1983). 

It seems that none of the theories surrounding the development of socialism in the hymenoptera are mutually exclusive and both kin selection and maternal manipulation have been a starting points for wasp and bee species to evolve into the complex societies we see today (Brian, 1983).

Video - Life Cycle of a Queen Honey Bee (Apis mellifera)

References:

Gould, I & Bolton, B 1988, The hymenoptera, Oxford University Press, Oxford.

Brian, MV 1983, Social Insects: ecology and behavioural biology, Chapman and Hall, London.

Dawkins, R 1976, The selfish gene, Oxford University Press, Oxford.

Image 1 – Yellowjacket (Vespula spp.) queen, gyne, and males on Goodisman Research Group, viewed 11 April 2015, <http://www.goodismanlab.biology.gatech.edu/Images_for_photos/Vmac%20queen,%20gyne,%20and%20males%20in%20nest.LG.jpg>

Image 2 - Red fire ant, Solenopsis invicta, castes and developmental stages on Goodisman Research Group, viewed 11 April 2015, <http://www.goodismanlab.biology.gatech.edu/Images_for_photos/Fire%20Ant%20Caste%20Development.AA3.Nov%202%202010.LG.jpg>

Image 3 – Multiple queens in a colony of Pheidole megacephala big-headed ants  St. Lucia, South Africa, viewed 11 April 2015 < http://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Pheidole/i-8BHB924/2/XL/megacephala14-XL.jpg> 

Video - Life Cycle of a Queen Honey Bee, youtube, viewed 11 April 2015 <https://www.youtube.com/watch?v=aNoqN-IX5qs>

Mechanisms behind eusocial societies in hymenoptera

What were the mechanisms that drove solitary hymenoptera into taking that first step into social societies and drove further advances into Eusociality? The main mechanisms that have been hypothesised are Kin Selection and Parental Manipulation (Brian, 1983; Gauld & Bolton, 1988). This blog entry will focus on the first mechanism - Kin Selection.

Kin selection relies heavily on genetic asymmetry in haplo-diploid systems – genetic asymmetry means a female has three quarters of her genes in common with her sister but only half in common with her mother and one quarter in common with her brothers (Brian, 1983). A female that assists in the rearing of her sisters will be genetically better off than having her own offspring which would only have half their genes in common (Brian, 1983). This is known as inclusive fitness and is stronger than direct fitness in haplo-diploid animals (Brian, 1983).

Oecophylla smaragdina (green weaver ants) adults caring for young in brood nest. Cairns, Queensland, Australia. Image courtesy of Alex Wild. 

Genetic fitness may also explain why most social hymenoptera produce very few males in comparison with females – males are much larger than workers and require more energy from the colony to produce but they provide very little and are essentially just breeding stock (Brian, 1983). Females however provide protection, brood care and food provisions making them a much wiser investment for the colony as a whole (Brian, 1983).

Apis mellifera (European honey bee) queen being tended to by her colony. Photo courtesy of Kathy Keatley Garvey.

Kin Selection alone cannot entirely answer the question of why socialism developed (Gauld & Bolton, 1988).  If kin selection alone was the driving mechanism then why don't other insects with haplo-diploid sex determination that display groups of adults and juveniles have more complex social structures like that of the Hymenoptera? The only insect species outside hymenoptera that are eusocial are Termites that are in the Blattodea order containing Cockroaches (Gauld & Bolton). Perhaps the answer is in the combination of both kin selection and parental manipulation. 

In the next blog entry I will discuss Parental Manipulation as a driver behind eusocialism in the hymenoptera and reproductive altruism. Here is a video that goes into more details about haplodiploidy in social insects.

References:

Gauld, I & Bolton, B 1988, The hymenoptera, Oxford University Press, Oxford.

Brian, MV 1983, Social Insects: ecology and behavioural biology, Chapman and Hall, London.

Image 1, Oecophylla smaragdina: Alex Wild: The diversity of insects, viewed 29 March 2015, <http://www.alexanderwild.com/Ants/Taxonomic-List-of-Ant-Genera/Oecophylla/i-kxngrZp/2/XL/smaragdina32-XL.jpg >

Image 2, Apis mellifera: Bug Squad: happenings in the insect world, viewed 29 March 2015, <http://ucanr.edu/blogs/bugsquad//blogfiles/14212_original.jpg>

Video: ‘Haplodyploidy in honeybees’, youtube, viewed 29 March 2015,  <https://www.youtube.com/watch?v=pkzTHwWwhQk>

Social Lives of Ants, Bees and Wasps...

Social life history in insects has evolved multiple times over diverse species and so understandably has a few different evolutionary paths and some very broad adaptations (Zablotny, 2009). Many solitary species of bees and wasps have communal nesting, where many females make their burrows within close quarters to each other but do not provide any provisions to each other (Gauld & Bolton, 1988). It is not certain whether communal nesting started to address a need for protection from predators, or due to adults returning to their birthplaces generation after generation or simply members of the same species just being mutually attracted to each other (Gauld & Bolton, 1988). Whatever the reason, this was the first step of socialism in the hymenoptera. 

Image 1: communal nest site of Cactus Bees (Diadasia australis). 

The different stages of socialism in insects can be difficult to grasp, so in 1971 the renowned American biologist E. O. Wilson established a standard vocabulary for describing the degrees of insect sociality from solitary to eusocial (Zablotny, 2009):

•  Solitary species do not have cooperative brood care, reproductive castes or overlapping generations.
• Quasi-social colonies share a nest, cooperate in brood care and also assist each other in providing food, nest building and protection but do not have overlapping generations or reproductive castes.
• Semi-social colonies are those that have some caste structure (a worker caste caring for a reproductive caste) as well as having cooperative brood care.

Image 2: semi-social nest of the stick-nest brown paper wasps (Ropalidia revolutionalis)
 in South East QLD 

• True social colonies are referred to as Eusocial. The generally accepted idea of a eusocial colony in insects is a colony which has cooperative brood care, an overlap of two or more generations & reproductive division of labour or ‘castes’ – in bees the castes are the reproductive queen, the non reproductive female workers and the reproductive male drones. 

Image 3: difference in honey bee (Apis mellifera) castes, from L to R: smaller non reproductive female worker, reproductive male drone and reproductive female queen. Notice the large abdomen on the queen for storage of eggs. The pale green dot on the queens back is common to help ID and spot queens in a hive. 

The haploid-diploid sex determination system assisted the evolution of social hymenoptera - Sex of offspring can be determined by the queen and she readjusts the sex ratio to suit the needs of the colony (Gauld & Bolton, 1988). Large numbers of female workers can be produced until the need for males arises. 

These however are not the only forms of socialism in the hymenoptera. There is social parasitism where a queen will take over an already functioning nest (either by killing or living alongside the original queen of another closely related species, parabiosis where 2 ant species may utilise the same nests and trails but do not share, lestobiosis where a smaller and larger species of ant may co-inhabit a nest and others (Gauld & Bolton, 1988).

I will leave you with a video of Dulosis or ‘slave-making’ which is common form of socialism in ant species - one species kidnaps pupae of another species to function as workers in their own nest.

References:

Gauld, I & Bolton, B 1988, The hymenoptera, Oxford University Press, Oxford.

Zablotny, J 2009, ‘Sociality’, Encyclopedia of insects. Oxford, United Kingdom: Elsevier Science & Technology, viewed 23 March 2015, Retrieved from <http://search.credoreference.com.elibrary.jcu.edu.au/content/entry/estinsects/sociality/0>

Image 1 – Cactus Bee Nests on The Happy Scientist, viewed 22 March 2015, <http://thehappyscientist.com/files/DailySciencePhoto/870c.jpg>

Image 2 – Stick-nest Brown Paper Wasp Ropalidia revolutionalis on Brisbane Insects, viewed 22 March 2015, <http://www.brisbaneinsects.com/brisbane_vespoidwasps/images/DSC_4461.jpg>

Image 3 – Bee Castes, viewed 22 March 2015,<http://www.brisbaneinsects.com/brisbane_vespoidwasps/images/wpe52.jpg>

Video – ‘Slave raid of P.americanus a obligatory social parasitic ant’, Youtube, viewed 22 March 2015, <https://www.youtube.com/watch?v=YdzEpd657RU>

Introducing the Hymenoptera: much more than aggressive stingers and jam jar raiders.

The Hymenoptera are one of the dominant life forms on Earth in both the number of species and in the diversity of life styles; however it is impossible to guess how many individual species there are with any accuracy (Austin & Dowton 2000). The order is so diverse there is no common name for the order like that given to the other insect orders, for example Coleoptera are commonly known as beetles, and Lepidoptera are referred to as butterflies and moths.

Four features are the main factors that separate the Hymenoptera from the rest of the insects and are crucial to the evolution and diversity of the order (Austin & Dowton 2000, Gould & Bolton 1988). These four factors are:




Figure 1: Aphidius ervi - biocontrol wasp attacking pea aphids. A parasitic wasp lays its egg inside a host,
the young feed on the host.
Image courtesy of www.alexanderwild.com.

1. Ovipositor is used for egg laying and venom delivery

 

2. Food is provided to the larvae by adults (bees/wasps create a cell for young and feed until pupation) or egg is laid in food source (such as parasitic wasps).

3. Larvae eat a range of foods – waste is stored in a gut cavity that does not form an intestine until the final stages of development.

 

4. Haplo-diploid sex determination: males are developed from non fertilised eggs therefore only receive mother’s genetics and females develop from fertilised eggs so genes are provided by mother and father.

Figure 2: honey bee feeding larvae inside cell.
Image courtesy of Maryann Frazier/Penn State.

 



These factors, along with environmental pressures have contributed to the amazing diversity of life seen in the order – there are parasites, parasites of parasites, herbivores, seed eaters, gall formers, specialised predators, pollinators and both social and solitary species (Austin & Dowton 2000).

 

 

 

Social Hymenoptera are said to represent the absolute peak of the evolutionary summit of invertebrates – social structures, agriculture and slave-keeping were present in Hymenopteran society well before humans even picked up their first tool (Gould & Bolton 1988). The video below shows how parasitic wasps can turn other insects into their 'slaves' or 'zombies'.

 

It has been suggested that the diversity of Hymenoptera is an example of how environmental pressures and ancestry can influence the evolution of a species and are useful subjects for the studies of how these processes can both play a part in understanding insect evolution (Strand 2000). It could be argued that the Hymenoptera are possibly the most important insects to evolutionary research.

Stay tuned for more from the exciting world of Hymenoptera.  

References:

Austin, AD & Dowton, M 2000, 'The hymenoptera: an introduction’, in AD Austin & M Dowton (ed.), Hymenoptera: evolution, biodiversity and biological control, CSIRO Publishing, Melbourne, pp. 3-7.

Gould, I & Bolton, B 1988, The hymenoptera, Oxford University Press, Oxford.

Strand, MR 2000, 'The effects of life history on development of the hymenoptera’, in AD Austin & M Dowton (ed.), Hymenoptera: evolution, biodiversity and biological control, CSIRO Publishing, Melbourne, pp. 11-16.

Figure 1: Alex Wild: The diversity of insects, viewed 10 March 2015. http://www.alexanderwild.com/Insects/Insect-Orders/Bees-Wasps-and-Sawflies/i-W8t97Kt/2/XL/Aphidius12-XL.jpg
 
Figure 2: Penn State News 2010, Penn State University, Pennsylvania, viewed 10 March 2015. http://news.psu.edu/story/301619/2014/01/27/research/common-crop-pesticides-kill-honeybee-larvae-hive

youtube video "Zombie caterpillar controlled by voodoo wasps": New Scientist 2008, Reed Business Information Ltd, viewed 10 March 2015. http://www.newscientist.com/article/dn14053