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Sweat the small stuff

Ground beetle (Anthia fornasinii) carrying a dead cicada. In South Africa these beetles are known under the charming name "oogpister" ("eye pisser") on the account of their ability to squirt defensive chemicals from their abdomen straight into the eyes of potential predators.

Ground beetle (Anthia fornasinii) carrying a dead cicada. In South Africa these beetles are known under the charming name “oogpister” (“eye pisser”) on the account of their ability to squirt defensive chemicals from their abdomen straight into the eyes of potential predators.

Recently I have been processing some of the 18,000+ photos I took during a recent trip to Mozambique, and yesterday one image caught my eye. It shows a large ground beetle carrying a dead cicada. I shot it rather casually one night in front of my tent in Gorongosa, and immediately forgot about it. But now, looking at it closely, I realized that I was guilty of the very same thing that I often preach against – I did not pay enough attention to the small things, and missed an interesting detail. Zooming in on the photo I noticed several ants milling around the beetle’s feet. More interestingly, one of the tarsi had a dead driver ant (Dorylus) permanently attached to it – the beetle had survived an attack by these notoriously vicious insects, which was quite impressive. But what were the other ants doing? I guess I will never know. I have made the same mistake in the past, where I would notice something interesting about the scene that I had shot, but only when it was much too late to go back and photograph it again.

A female Harlequin beetle (Acrocinus longimanus) from Guyana. The body of these insects is a vibrant ecosystem for several species of arachnids.

A female Harlequin beetle (Acrocinus longimanus) from Guyana. The body of this insect is a vibrant ecosystem for several species of arachnids.

But there is one thing that greatly helps in preventing this from happening – as Louis Pasteur succinctly put it, “In the field of observation, chance favors the prepared mind.” In the field of nature photography, the more you know about your subject, the more likely you are to notice something interesting or unusual, and refocus on that. My best example comes from Guyana, where a few years ago I found a gorgeous Harlequin beetle (Acrocinus longimanus). After taking a few photos of the animal I was about ready to let it go when suddenly some microscopically tiny  object ran across its body. I felt a spark in my brain reignite some old, long unused synapses, and recollections started flooding in – “That looked like a small scorpion. No, a pseudoscorpion. They are phoretic. One species is found only on Harlequin beetles. Cordylochernes scorpioides, that’s it!”

Large fig trees in South American rainforests serve as hosts to the spectacular Harlequin beetle, which completes its larval development in the wood of these plants. The body of this giant insect is in itself a vibrant ecosystem for several species of smaller animals. Hundreds of mites hide under the wings and in crevices of the beetle’s body, using the insect as a convenient way to move from place to place. The mites also serve as food for another passenger, the pseudoscorpion. But the mites are not the main reason why pseudoscorpions embark on the beetle’s back.

A phoretic pseudoscorpion (Cordylochernes scorpioides) uses the body of the Harlequin beetle to move from one fig tree to another, and to find mating partners and food.

A phoretic pseudoscorpion (Cordylochernes scorpioides) uses the body of the Harlequin beetle to move from one fig tree to another, and to find mating partners and food.

These arachnids spend their lives on the same fig trees that the beetles need to develop and where they seek mating partners, and thus the pseudoscorpions can be assured that by hitching a ride on a harlequin beetle they will end up on another tree of the same species. This also means that the beetle’s back is a great place to meet new partners who hopped on it to look for new fig trees to colonize, and a lot of sexual activity takes place among pseudoscorpions under the covers of the beetle’s wings. Some male pseudoscorpions never leave the beetle because they know that with each landing on a fig tree new females will embark, giving them more chances to pass on their genes. And because some time ago I had read a study that described all this, I did not miss the opportunity to photograph this fascinating symbiosis. Now, if only somebody wrote something about beetles and ants…

Unidentified phoretic mites on the body of a Harlequin beetle serve as food to pseudoscorpions.

Phoretic mites on the body of a Harlequin beetle serve as food to pseudoscorpions.

I missed this one – an African assassin bug from Guinea also has phoretic mites and pseudoscorpions, but I only noticed them while processing this photo. It is possible that their natural history parallels that of the Neotropical Harlequin beetle and its passengers.

I missed this one – an African assassin bug from Guinea also has phoretic mites and pseudoscorpions, but I only noticed them while processing this photo. It is possible that their natural history parallels that of the Neotropical Harlequin beetle and its passengers.

Mozambique Diary: Somebody has to clean this mess

The Green dung beetle (Garreta nitens)is a pretty, diurnal species.

The Green dung beetle (Garreta nitens) is a pretty, diurnal species.

A friend of mine once compared holding a dung beetle in your hand to kissing a dog on the snout – both feel kind of good, until you think of the last thing they have probably been rubbing against. At least with dogs there is some room for other options, but there is no such ambiguity with the beetles. Still, it is difficult not to be impressed with the incredible forms and colors of these insects, and I had to constantly remind myself to be careful while handling the gorgeous dung beetle specimens that Bruno de Medeiros, a Harvard coleopterist participating in our Cheringoma biodiversity survey, kept bringing for me to photograph. For you see, the best and most effective way to collect these beetles is to lure them with a tasty bait. And there is no better bait than dung of an omnivorous mammal, and none is more omnivorous than a human. Dung beetle specialists have long been searching for the Holy Grail of Scarabaeology – a synthetic bait that attracts a wide variety of species – but, alas, they have not yet found it. And so, Bruno, like an expectant mother, was forced to eat for two (or rather several hundred) in order to produce enough bait to fill the dozens of pitfall traps needed to sample dung beetles at each of our survey’s sites.

Bruno de Medeiros with one of the largest dung beetles found in Gorongosa, Pachylomerus femoralis.

Bruno de Medeiros with one of the largest dung beetles found in Gorongosa, Pachylomerus femoralis.

We still don’t know how many species of dung beetles came to Bruno’s carefully baited pitfalls – identifying tiny aphodiines and other cryptic forms will take some time – but in his estimation at least 100 species, perhaps more, are to be expected. This is really good news for the Gorongosa ecosystem. Although the park lost a large proportion of its mammal population during the civil war of 1975-1992 and, consequently, its dung beetles surely must have suffered from the sudden decline in availability of their food resources, all original elements of their fauna are probably still in place. This means that as the large mammals return, and populations of most herbivores already show quickly accelerating growth rates, dung beetles will be able to build up quickly and resume their thankless but invaluable services.

Female Heliocopris sp. taking off, apparently not satisfied with the quality of the dung she found.

Female Heliocopris sp. taking off, apparently not satisfied with the quality of the dung she found.

Dung beetles are critically important members of savanna communities that dominate Gorongosa, and without them and their waste removal labor the place would quickly sink under layers of dung produced by thousands of mammalian grazers and browsers. Their ability to return nutrients trapped in dung into the soil also supports the positive feedback loop between rapid vegetation growth and herbivory. The ecosystem services provided by dung beetles thus carry actual, calculable monetary value – I am not sure what that value is in Gorongosa, but in the United States the dung removal services by beetles is estimated to save the cattle industry $380 million per year. In Australia dung beetles imported from Africa and other places saved the cattle industry from a total collapse after it became apparent that local insects were not adapted to processing manure of non-native mammal species; New Zealand is also considering a similar move to save itself from an ocean of cattle and sheep dung that threatens to engulf the islands.

Male Heliocopris andersoni, one of the largest and most impressive dung beetles in Africa.

Male Heliocopris andersoni, one of the largest and most impressive dung beetles in Africa.

But dung beetles are not only useful and pretty, they are also supremely cool – a recent study demonstrated that they are the only insects known to navigate using the position of the Milky Way and other galaxies. Only humans (and possibly a few other animals, but it has never been conclusively proven) use the position of celestial bodies to find their way around.

And although I quickly learned that I should hold my breath and discreetly reach for a bottle of hand sanitizer every time Bruno brought me a new specimen, it was always a thrill to see a new animal. The high dung beetle richness we found on the Cheringoma Plateau shows that Gorongosa is well on its way to full recovery, and its cleanup crew is alive and well.

A time lapse movie spanning 10 hours of dung beetle activity, showing what happens to warthog dung in Gorongosa. (Click here for a high quality version of the movie.)

Plum dung beetles (Anachalcos convexus) do not display sexual dimorphism, and both males and females form dung balls; this species is also often seen feeding on dead insects.

Plum dung beetles (Anachalcos convexus) do not display sexual dimorphism, and both males and females form dung balls; this species is also often seen feeding on dead insects.

Mozambique Diary: Manticora redux

The head of a Manticora larva blocking the entrance to its burrow.

The head of a Manticora larva blocking the entrance to its burrow.

Some weeks ago I wrote about the Monster Tiger Beetle (Manticora) that I had found in the savanna of Gorongosa. These insects are powerful predators, hunting grasshoppers and other small invertebrates using their enormous mandibles. The larvae of Manticora are similarly carnivorous, but rather than actively pursuing their prey the way their parents do, they are sit-and-wait predators. At that time I had not been able to see or collect Manticora larvae, but tonight I finally managed to snag one.

Like other tiger beetles, the larvae of Manticora hunt from the safety of their narrow, nearly vertical burrows in the sand. Their soft body is safely tucked inside the tunnel, and the only thing that is visible on the surface is a large, heavily sclerotized head and pronotum, both of which form a shield that blocks the access to the burrow. The mandibles of a Manticora larva are pointing upwards so that any insect unlucky enough to step on the head is instantly grabbed by its leg and pulled underground. Imagine walking down the street and stepping on one of those round metal plates that cover sewer manholes, only the plate turns out to be the head of monster, and you are instantly sucked underground – this is what it must feel to a cricket or an antlion as it is being dragged by Manticora.

Only the head and pronotum of a larva of Manticora is heavily sclerotized, while the rest of the body is soft and safely tucked inside the burrow. Notice the anchor-like structure on the 5th abdominal segment.

Only the head and pronotum of a Manticora larva are heavily sclerotized, while the rest of the body is soft and safely tucked inside the burrow. Notice the anchor-like structure on the 5th abdominal segment.

I found a small aggregation of Manticora larvae on one of the sandy paths in the Chitengo camp and watched them for a little while. The aggregation consisted of 10 larvae of different ages, the smallest ones with the head diameter of about 5 mm, the largest 10-12 mm wide. A nearby lamp was attracting a lot of insects, and every 20-30 seconds an insect would invariably land near one of the Manticora burrows. The larvae clearly used their eyes to locate the prey and stretched out as far as they could out of the burrow to be ready when an insect gets really close. If the insect got within a couple of millimeters of the head, the mandibles snapped around the insect’s leg and the victim was instantly pulled underground. Interestingly, the larvae were clearly able to assess their chances of success: if the potential victim appeared to be too large to be pulled inside the burrow, rather than catching the insect’s leg the larva would flick its head and toss the insect away.

This cricket is done for – a Manticora larva grabbed its front leg and is dragging it down the burrow.

This cricket is done for – a Manticora larva grabbed its front leg and is dragging it down the burrow.

It took me a while to figure out how to extract one of the larvae out of its burrow. At first I tried digging, but the tunnels turned out to be very long, and the hard, caked soil made digging very difficult. Eventually, I used the insect’s own voracity to catch it – I gently touched the head with the forceps, and when the mandibles snapped around it I grabbed the head and pulled the larva out. It was not easy as the 5th abdominal tergite of the larva is modified into a large, spiny structure that effectively anchors the animal in its burrow. The larva’s morphology reminded me of marine polychaete worms that use a similar tactic for catching prey from the confines of their burrows.

A Manticora larva, just like its parents, is a voracious killing machine.

A Manticora larva, just like its parents, is a voracious killing machine.