Why look like a spider?

"Why did the fly fly? Because the spider spied'er." - Anon.

Not every resemblance is a case of mimicry. An image of the Tephritid fly Goniurellia tridens with spider-like or ant-like patterns on its wing went viral in recent times and some have pointed out that this might be a case of wishful thinking. A little more than a week ago, I was observing a tiny day-flying moth in the Western Ghats of India and its behaviours. It seemed to make quick movements after landing and before coming to rest and then it would wave its hind legs slowly. It also made slight shifts of the forewings giving it the distinct impression of a jumping spider (Salticidae). 

Here are some not so brilliantly captured videos:

I cannot find a matching Salticid model but the posture and appearance make the mimicry seem perfectly plausible. Unlike the ants, which are dreaded by most of the smaller majority it is harder to think of a jumping spider as being recognized and avoided.

Here is a Salticid as seen from the side

Salticus scenicus from California by Kaldari (Wikimedia Commons)

Roger Kendrick has kindly identified this as belonging to the family Glyphipterigidae

Now there are ways to test if the resemblance is just accidental or if it really enhances the survival of the mimic. When I posted this on Facebook, I was pleasantly surprised to know that the Tephritid pattern which is quite widespread has actually been put to some test by an old friend, Dinesh Rao and his colleagues. Some of the earlier studies on the Tephritids with experiments involving wing transplantation suggests that the behavioural part is vital and that this seems to be specifically to avoid predation by Salticids. It seems like much more work is needed and we may well find many more cases of Salticid mimicry. But why only Salticids, is it because they are the most active on vegetation? And then we have some Salticids themselves being mimics of ants.

Brenthia sp. (from Rota & Wagner, 2006)

 

Here are some more suspects -
http://bugguide.net/node/view/433093 (another moth)
http://www.flickr.com/photos/orionmystery/8266380277/ (Amphientomidae, Psocoptera)

See also the excellent and interesting videos on http://naturedocumentaries.org/4450/predator-mimic-fly/

Rear end of Amycle sp. (from Zolnerowich 1992)

PS:  Have just examined the history and it seems that Tom Eisner was the first to suggest spider mimicry in Zonosemata.


Many other "microlepidoptera" have the habit of raising or waving their hindlegs. Given that salticids are considered masters of taking indirect routes to their prey, it seems like waving legs from the blind hind end might have a benefit not unlike that of the false heads of lycaenids. Perhaps salticids choose to circumvent this false head and come into the visible zone of the potential prey's zone of vision, thereby making them less liable to fall prey.


PS: In July 2015, during the monsoons, I noticed this common tetrigid with prominent white (maxillary?) palps making these jumping-spider-like motions. The grasshopper itself moves in jerks and it seems that the resemblance might have a value in escaping predators.

Acknowledgements

Dinesh Rao for pointing out the work he is doing and allowing me to post without fear of sounding like a complete crank.

A salticid peers from the cover of a fern (Wynaad)

References

• Dinesh Rao, Francisco Diaz-Fleischer (2012) Characterisation of Predator-Directed Displays in Tephritid Flies. Ethology 118(12):1165–1172.
• Rota J, Wagner DL (2006) Predator Mimicry: Metalmark Moths Mimic Their Jumping Spider Predators. PLoS ONE 1(1): e45. doi:10.1371/journal.pone.0000045
• Jin-Nan Huang, Ren-Chung Cheng, Daiqin Li, and I-Min Tso (2010) Salticid predation as one potential driving force of ant mimicry in jumping spiders. Proc Biol Sci. 2011 May 7; 278(1710): 1356–1364.
• Gregory Zolnerowich (1992) A Unique Amycle Nymph (Homoptera: Fulgoridae) That Mimics Jumping Spiders (Araneae: Salticidae). Journal of the New York Entomological Society 100(3):498-502.
• Whitman, D.W, Orsak L & Greene E. (1988) Spider mimicry in fruit flies (Diptera: Tephritidae): Further experiments on the deterrence of jumping spiders (Araneae: Salticidae) by Zonosemata vittigera (Coquillett). Ann. ent. Soc. Am. 81:532-536.
• David B. Richman and Robert R. Jackson (1992) A review of the ethology of jumping spiders (Araneae, Salticidae). Bull. Br. arachnol. Soc. 9(2):33-37.
• Eisner, T. (1985) A fly that mimics jumping spiders. Psyche 92:103-104.
• Greene E, Orsak LJ, Whitman DW. (1987) A tephritid fly mimics the territorial displays of its jumping spider predators. Science. 236(4799):310-2.
• O'Brien, L.B. (1967) Caliscelis bonellii (Laterille), a European genus of Issidae new to the United States (Homoptera:Fulgoroidea). Pan-Pacific Entomologist 43:130-133 [Again male-limited resemblance to a jumping spider! Compare this]

Be like a bee

I have written in the past about ant-mimicry (Why look like an ant?), and last week I was reminded how good their relatives, the bees and wasps, are as models for Batesian mimicry. It was just by chance that I noticed this yellow spot on a rock beside a stream running through the forest. 

It was evident that this was a moth, a hawk-moth for sure, confirmed by looking at the hooked tip to the antennae. The remarkable similarity in pattern and size to carpenter bees of the genus Xylocopa is readily evident. As kids we used to play a trick with Xylocopa males that would perch atop wooden posts. Toss a pebble in the direction of the male and it would set off and pursue the pebble. Handling a dead carpenter bee was a painful lesson on how spiny and hard they are. Females can sting but they rarely need to use it. There is probably no predator of adult Xylocopa bees. Little wonder then that several species in the day-flying hawk-moth genus Sataspes have been selected to appear like carpenter bees (other day-fliers like Cephonodes look like clear-winged bees). The genus Sataspes does not seem to be well known in southern India and this observation may be among the few reports from southern India.

Species in the genus appear to show considerable variation within populations in the distribution of blue and yellow on their body and wings. Several of these variants have been described in the past as species and the exact determination of species may be reliably established only by dissecting out their genitalia (which show species-specific lock-and-key patterns). In 1900, a year before he died of malaria, Lionel de Niceville described a species from Burma:

S. tagalica (=S. hauxwelli) and model

"I have named this handsome moth (which is unique) after Mr. T. A. Hauxwell, Deputy Conservator of Forests, who is an enthusiastic collector of birds and Lepidoptera. It is a beautiful mimic of the very common large blue carpenter bee, Xylocopa auripennis, Lepeletier, a male of which I have figured-for the first time-for comparison ..." JBNHS 13:173

Some people find the evolution of mimetic forms too implausible to occur by random processes and those that question evolution pose the question as to how the "exact" same pattern could arise. Interestingly enough there is considerable variation within the mimics and it is actually not an exact imitation. Here are a couple of Xylocopas (unidentified) from southern India just for a sampling.

A Xylocopa from the W. Ghats

A Xylocopa from Bangalore

Looking at the variations in Sataspes it is clear that a series of characters are being mixed in various forms and species.Yellow bands, thorax, tufts, bluish wing shine and so on.

Sataspes xylocoparis described by A G Butler in 1875

Writing about Xylocopa aureipennis in 1922, Cedric Dover notes incredulously:

In addition to the localities noticed by Bingham, the Indian Museum also possesses specimens from the Parjiling District, the Naga Hills and Sibsagar in Assam, South India and Nepal. The species is supposed to be mimicked by a Sphingid moth (Sataspes hauxwelli), which according to De Niceville (Journ. Bomb. Nat. Hist. Soc. XIII, p. 174) was "a beautiful mimic of the very common large blue carpenter-bee Xylocopa auripennis, Lepeletier." The wings of the moth are a deep indigo-blue with bronze markings, which scarcely resembles the wings of the bee, and in the cabinet the whole insect seems entirely different.
De Niceville does not say that the bee and the moth were taken together, and in the absence of definite field-observations, the moth has little claims to being a mimic of the Xylocopa.

My own impression was that the moth above was the right size, shape and colour to give the impression of a carpenter bee.

Although carpenter bees are free from predators, they are not free from parasites and their immature stages probably have predators. A peculiar feature of carpenter bee females is a cavity on the first abdominal segment, known as the acarinarium, which is home to mites of the genus Dinogamassus. Nobody quite knows what the role of these symbiotic(?) mites are. Dr B. Mallik, an acarologist (and one of my teachers) at the entomology department in the University of Agricultural Sciences (Bangalore) showed me some of these mites under a microscope a few years ago pointing out that they stack up in a toroidal pattern.

The fact that so few records of these amazing day-flying moths exist is either due to their rarity or the fact that we have so few people keeping an eye on life around them.

References

• Butler, AG (1875) Descriptions of new Species of Sphingidae. Proceedings of the general meetings for scientific business of the Zoological Society of London 238-261 
• De Niceville, Lionel (1900). On new and little-known Lepidoptera from the Oriental region. J. Bombay Nat. Hist. Soc. 13:157-175.
• Dover, Cedric (1922) A note on the bees of the genera Xylocopa and Bombus in the Indian Museum. Records of the Indian Museum 24:85-89
• Sataspes tagalica, Sataspes xylocoparis, Sataspes infernalis 

Postscript
1-May-2013: Ian J. Kitching of the Natural History Museum notes:

... all the evidence now points towards it being the first representative of infernalis from SW India. All other specimens I have seen from the Western Ghats are the relatively non-metallic forms as shown on SEP. None have the strong blue sheen on the wings of your specimen. ..., the moth does look a bit more like S. tagalica but this usually has a greenish metallic sheen and the females (which your moth is) never have a yellow thorax, only the males. That said, there is a definitive feature that could settle the matter BUT it is on the underside of the abdomen. This is a long shot but do you have a photo in which the colour of the underside of the terminal segments of the abdomen is visible, even slightly. These are yellow in infernalis/xylocoparis and black in tagalica.

All that said, no Sataspes in our collection of any species has the subdorsal rows of yellow spots; they either have more extensive yellow bands (see xylocoparis on SEP) or broad central patches (see tagalica on SEP). So I am minded to think that this may be a new species, or at least a distinctive subspecies of infernalis.