Insecta

Insects – Collembola, Protura, Diplura, Archaeognatha, Thysanura & Pterygota (winged insects).

Retrachydes thoracicus – times four!

/ Ted C. MacRae / 14 Comments

Disclaimer—these are not great photos!

A few days ago I posted this little quip as my status on Facebook: “Cool! Found a Retrachydes thoracicus thoracicus on the sidewalk outside my hotel!” I chuckled a little as I posted it, knowing that only a select few who read it would know what the heck I was talking about (of course, a right click to select “Search with Google” reveals the answer instantly). Of course, it is a species of longhorned beetle (family Cerambycidae) that apparently is found commonly in South America. I wanted to take some photographs of the beetle to show those who didn’t do the Google search just what it looked like. Unfortunately, the beetle was already somewhat moribund when I found it, and no matter how much I coaxed and prodded it on the stick I placed it on, it just looked… well, dumb. Legs out of position, antennae hanging limply, and the beetle itself laying prostrate on the branch, as if it barely had the strength to hang on (which actually was the case). Shame—it sure is an attractive species, with its densely pubescent and transversely gibbous pronotum (obviously the source of its name) and striking orange-banded antennae. C’est la vie!

Lately I’ve been trying to get a better handle on choosing backgrounds when I photograph insects, no longer content with the often busy and distracting backgrounds that show up in photographs taken completely in situ. It’s often a simple matter to hold the object on which the insect is sitting in front of something that gives the desired background effect, and having this perfectly calm yet strikingly attractive beetle to work with seemed to invite experimentation. I’m also trying to get a better feel for how to use higher ISO settings to make it easier to get these various “non-black” backgrounds while still using flash to get acceptable depth of field with the subject itself. Below are four of the better shots that came out of the session (yes—sadly, these are the “better” ones). I’m loathe to go below 1/160 sec exposure because of motion blur and would like to keep aperture settings quite small, so fairly high ISO settings are required to get the background effects I’m looking for. I think I’ve learned that ISO 1000 is about as high as I can go before the background gets unacceptably noisy—at small sizes the photos look fine, but open them up larger size and you’ll see what I mean. Anyway, ignoring the composition and noise issues, which background do you like best?

ISO 1000, 1/160 sec, f/14 - cloudy sky background

ISO 1600, 1/160 sec, f/14 - pavement background (close)

ISO 1600, 1/160 sec, f/14 - pavement background (more distant)

ISO 1600, 1/160 sec, f/14 - pavement background (foliage)

Copyright © Ted C. MacRae 2012

Chicharra que canta, calor adelanta

/ Ted C. MacRae / 5 Comments

Dorisiana drewseni - male singing

There is a species of cicada (“chicharra” in Spanish) that strikes me as quite common in the central Humid Pampas region of Argentina. I saw numerous individuals during March of last year at La Reserva Ecologica Costanera Sur (where these photos were taken), and again during the past week I’ve noted them abundantly in the trees around my base station in western Buenos Aires Province. Thanks to cicada expert Barry University’s Allen Sanborn (apparently himself an endangered species), I now know these to be the species Dorisiana drewseni (Stål, 1854), occurring in Argentina, Uruguay and southern Brazil (Aoli et al. 2010).

Dorisiana drewseni, female resting on thistle

As in North America, the song of the cicada is associated with the dog days of summer and their midday heat. “Chicharra que canta, calor adelanta” is a Spanish idiom that loosely translates to “Cicadas singing, heat follows”. March is late summer in Argentina, and the days can still be quite hot even at temperate latitudes (yesterday was 34°C, or 93°F). Despite being half-a-world away from St. Louis, the droning song of the cicada sounds a bit like home in late August. While I was at the Reserva last March I really wanted to photograph a male in the midst of song, but the above photo was the only shot I managed from several males. Singing males are extremely difficult to approach to within even a long-handled net’s reach—much less a camera lens’ focal distance. I think the only reason I was able to photograph the male above was because I approached him from slightly below and behind (though certainly still within the field of vision of those huge, bulging eyes). One shot was all I got, and off he flew, shrieking noisily as he crashed and thrashed through the foliage before reaching open air and completing his escape.

Females, on the other hand, seemed to be much more approachable (perhaps because they, unlike singing males, never do anything to draw attention to themselves). The female in the photo above was calmly sitting on a thistle-like plant at eye-level, never flinching at my approach (albeit cautious) and calmly staying put while I snapped a few photos. One look at her tattered wings, however, suggests that she had already seen better days and perhaps no longer had the strength to attempt to flee (maybe even expectedly awaiting predation at this point in her life).

A second female rests calmly on a tree branch

Not long after taking the photographs of the first female, I saw another female sitting on a tree branch. As I mentioned, females don’t call attention to themselves the way males do, so finding females is a bit more of a crapshoot—I only happened to see this one because she was on a tree branch at eye level with an unobstructed view hanging right next to the path I was following. Obviously much fresher and in better shape than the previous female, she nevertheless allowed me to get as close as I wanted, with the photographs above and below representing the two that I am happiest with.

That's one heck of a cibarial pump!

I haven’t had quite the same luck during the present trip in securing one of these—probably because my lone attempt so far was during the heat of the day on a day that was already warm enough. Come to think of it, I didn’t manage any of the above photographs last year until quite late in the afternoon when temperatures began to drop off a bit. We’ll see what the next few weeks brings—I am still committed to getting the money shot of a male in the midst of his song. Chicharra que canta, Ted adelanta!

REFERENCE:

Aoki, C., F. Santos Lopes & F. Leandro de Souza. 2010. Insecta, Hemiptera, Cicadidae, Quesada gigas (Olivier, 1790), Fidicina mannifera (Fabricius, 1803), Dorisiana viridis (Olivier, 1790) and Dorisiana drewseni (Stål, 1854): First records for the state of Mato Grosso do Sul, Brazil. Check List 6(1):162–163.

Copyright © Ted C. MacRae 2012

The most common beetle in Argentina

/ Ted C. MacRae / 7 Comments

Astylus atromaculatus | Buenos Aires Province, Argentina

I don’t know if this is truly the case, but Astylus atromaculatus (family Melyridae) is one of only a few beetles in the country that actually has two Spanish common names—”astylus moteado” and “siete de oro” (meaning “spotted astylus” and “seven of gold”, both names referring to black splotches on the elytra). It is also the only beetle that I’ve seen everywhere I’ve been in the country—north and south, soybean fields and cornfields, countryside and city. I have yet to visit a soybean field where I don’t see them, perhaps nibbling on a leaf here and there but mostly just mating, and they can be downright overwhelming in cornfields (see this post with photos of the adults dripping from corn tassels, literally!). For all their ubiquity, however, their economic impact seems more nuisance than substantive. Corn breeders complain about interference during tasseling, and larval feeding on seeds during or just after germination seems to be on the rise due to increased use of conservation tillage, but overall this species seems to be more bark than bite.

Copyright © Ted C. MacRae 2012

Eriopis connexa on soybean in Argentina

/ Ted C. MacRae / 7 Comments

Eriopis connexa adult on soybean | Buenos Aires Province, Argentina

Congratulations to those of you who correctly guessed the identity of the “subject” in ID Challenge #16 as the ladybird beetle Eriopis connexa (family Coccinellidae). This is one of the most common ladybird beetles in Argentina, and during the past few weeks I have seen large numbers of these beetles in the soybean fields that I have been visiting. Coccinellids in Argentina are among the easier the groups to identify to species thanks to the excellent website Coccinellidae of Argentina. Identifying the “meal,” however, proved to be a little more difficult. Most people guessed aphids, a natural choice, but soybean aphids have not yet made it to the soybean fields of South America (thankfully!), so the victims of these predaceous beetles must be something else. There was a clue in the challenge photo that at least one person picked up on (but didn’t make the connection) in the form of small black globs stuck to the hairs of the plant on which the beetle was sitting. These are actually the fecal deposits of the bean thrips, Caliothrips phaseoli (order Thysanoptera, family Thripidae) (which I covered a year ago in A thrips is a thrips…), which for the past two seasons now has built up large populations on soybeans in Argentina. In fact, an adult bean thrips (yes, “thrips” is the correct singular form) can be seen in the above photo (which I did not notice while I was taking the photo). I’ve not yet witnessed these beetles actually feeding on a thrips, but the large numbers of thrips and beetles and near absence of any other suitable prey item makes the association almost a given.

Eriopis connexa larva on soybean | Buenos Aires Province, Argentina

Not only are the adult beetles numerous on the plants, but eggs and larvae as well. Larvae are every bit as brightly colored as the adults, with a color scheme that leaves little doubt regarding their association. In the case of this larva, I watched it roam back and forth across the soybean leaf, pausing momentarily and apparently eating something—thrips eggs I presume.

Congratulations to Mr. Phidippus and Dennis Haines, who tie for the Challenge win with 14 points each, while Gustavo and Dave tie for the final podium spot. Mr. Phidippus, however, easily takes the overall win in BitB Challenge Session #5 with a whopping total of 57 points. Mr. Phidippus—contact me for your loot! Dennis Haines and Tim Eisele take 2nd and 3rd overall honors, and full standings for BitB Challenge Session #5 are shown below.

Commentor IDC#14 SSC#10 IDC#15 Bonus SSC#11 Bonus IDC#16 Total
Mr. Phidippus 11 11 9   12   14 57
Dennis Haines 9 4 2   10 1 14 40
Tim Eisele 8 6 2   13   6 35
Roy 5 6 7   10     28
Mike Baker 7   9       10 26
Dorian Patkus     9   11 4   24
David Winter 3   9       10 22
Gustavo             12 12
HBG Dave             12 12
Marlin 12             12
FlaPack 10             10
Laurie Knight 2       8     10
Doug Yanega         9     9
Brady Richards       4   3   7
John Oliver   6           6
George Sims 2 2 2         6
Richard Waldrep   6         6
Arpad Hervanek 4             4
Roxane Magnus 4             4
dragonflywoman       4     4
Wayne K         4     4
itsybitsybeetle         4     4
fatcatfromvox 2             2
Emily Gooch 1             1
Sean Whipple     1         1
Jon Q             1 1

 

Copyright © Ted C. MacRae 2012

Lord of the flies!

/ Ted C. MacRae / 23 Comments

I happened upon a rather interesting scene last week in a soybean field in northern Argentina (Chaco Province). This assassin bug (family Reduviidae) had captured and was feeding on an adult stink bug of the species Piezodorus guildinii—an important pest of soybean in Argentina and Brazil (where it is known by the common names “chinche de la alfalfa” and “chinche verde pequeño”, respectively). Assassin bug predation is always interesting enough itself, but what made this scene especially fascinating was the large congregation of flies surrounding and even crawling upon the predator and its prey. I had not witnessed something like this before, but it seemed clear to me that the flies were engaging in kleptoparasitism—i.e, stealing food. I’ve gotten into the habit of keeping a full set of extension tubes mounted on the camera with my 100mm macro lens—this not only provides the most useful (for me) range of magnification but also serves as a convenient and easy-to-use field microscope. Through the viewfinder I could see that there were at least two markedly different types of flies involved—more abundant, small, brown flies that I presumed (incorrectly, as it turns out) to be some type of drosophilid (vinegar fly), and a few larger, black flies that were completely unfamiliar to me. The flies were apparently feeding on fluids from the stink bug prey but also crawled all over the assassin bug as it fed. The assassin bug seem unencumbered in its feeding by the presence of the flies, but periodically it would slowly wipe its forelegs over its head to dislodge flies that had settled onto it. Just as quickly as they flew away, however, they crawled back.

The assassin bug, on the other hand, I recognized as very likely a species of Apiomerus—a large, exclusively New World genus known in North America as “bee killers” for their habit of sitting on flowers and ambushing visiting bees for prey. The prey selection behaviors of these insects, however, are more generalist than the name implies, as can be seen by these photographs. To verify my generic ID and possibly obtain a species ID, I sent some of these photos to Dimitri Forero at the Heteropteran Systematics Lab at University of California-Riverside. Dimitri is revising portions of Apiomerus (e.g., Berniker et al. 2011) and working on a general phylogenetic hypotheses for the genus. In the past he has been quite helpful in fielding questions from me about these bugs, and within a few hours Dimitri replied to inform me that the assassin bug was, indeed, a member of the genus Apiomerus, likely representing the common, widespread species A. lanipes (ranging from Panama to Argentina), based on its coloration, locality, and relative size. Update 12 March, 3:07 pm—After seeing the last photo in this post (which I did not send to him initially), Dimitri wrote to say the ventral abdominal pattern was not characteristic of A. lanipes. He asked about its size, to which I replied that it was about the same length but maybe a little less robust than A. crassipes (eastern North America). He later added, “I now think that this is A. flavipennis Herrich-Schaeffer, 1848. It is very similar to A. lanipes, but a lot smaller (lanipes is really robust), and with the abdomen with black and white patches, whereas in lanipes the abdomen is always black. I checked some series of specimens that I have here and, I am pretty sure now of the ID. I have material from Argentina as well. In some specimens that coloration of the corium varies, but the original description says it is yellow with a “hairy” pronotum, which fits very nicely your photos.” Apiomerus flavipennis is known from Argentina and Southern Brazil only.

Quite unexpectedly, Dimitri also noted that at least some of the flies could belong to the family Milichiidae. He first became aware of these flies after seeing a photograph of Apiomerus showing something similar and suggested Milichiidae online as a possible source for more information. This remarkably informative  website by milichiid expert Irina Blake, who dubs species in the family as “freeloader flies”, is a model for how websites dealing with obscure insect taxa should be organized and populated (and features on the home page a great photo of ant-mugging flies taken by our favorite myrmecophile). At any rate, I forwarded my photos to Irina and within minutes received her response that the bigger black flies most probably represent the cosmopolitan Milichiella lacteipennis and the smaller flies a species of the family Chloropidae (of “dog pecker gnat” fame) in the subfamily Oscinellinae, noting that she has seen similar (or the same?) chloropids in other photos as well engaging in kleptoparasitism.

Not long after receiving the first reply from Dimitri, I got another message from him with a link to a very interesting paper by Eisner and colleagues (1991), who recorded freeloader flies in Florida preferentially attracted to stink bugs and leaf-footed bugs (family Coreidae) being preyed upon by the orb-weaving spider Nephila clavipes. Olfactory stimuli were already suspected to be involved in attraction of milichiids and also chloropids (Sivinski 1985); however, Eisner et al. (1991) experimentally demonstrated that milichiid attraction was tied to specific components of defensive sprays in several pentatomid and coreid species (including P. guildenii, the prey species in this series of photographs). The defensive sprays of the bugs were generally ineffective at preventing predation by the spiders (and apparently this is the case for A. lanipes and other reduviids as well), thus serving as a signal to milichiids and chloropids not only of the presence of a food source but perhaps also assisting search for mates in a density dependent fashion (Sivinsky 1985). Milichiid attraction to hymenopteran prey, richly endowed with integumental glands themselves, has also been documented; the Eisner study raises the question whether these types of prey are also detected from chemical cues.

REFERENCES:

Berniker, L., S. Szerlip, D. Forero and C. Weirauch. 2011. Revision of the crassipes and pictipes species groups of Apiomerus Hahn (Hemiptera: Reduviidae: Harpactorinae). Zootaxa 2949:1–113.

Eisner, T., M. Eisner & M. Deyrup. 1991. Chemical attraction of kleptoparasitic flies to heteropteran insects caught by orb-weaving spiders. Proceedings of the National Academy of Sciences of the United States of America 88:8194–8197.

Sivinski, J. 1985. Mating by kleptoparasitic flies (Diptera: Chloropidae) on a spider host. Florida Entomologist 68(1):216–222.

Copyright © Ted C. MacRae 2012

Sharpshooter

/ Ted C. MacRae / 1 Comment

Pawiloma victima | Buenos Aires Province, Argentina

With around 20,000 species worldwide, leafhoppers (family Cicadellidae) are not only the largest family of true bugs (order Hemiptera) but also one of the top ten largest families of all insects. My favorite are “sharpshooters” (subfamily Cicadellinae)—large, distinctive, brightly colored species, and the individual shown in the photo above is no exception. I found it today in a soybean field in western Buenos Aires Province. Leafhoppers do have a reputation for difficult taxonomy due to their diverse numbers and often similar appearance (many can only be distinguished by examination of male genitalia); however, the distinctive color patterns of sharpshooters make many of them relatively easy to identify. The best resource for doing this is Sharpshooter Leafhoppers of the World (Wilson et al. 2009), an excellent website with a searchable photo database of nearly all 2,400 recognized species in the subfamily. According to that site, there are 64 species of sharpshooters recorded from Argentina, with the individual in this photo being a dead ringer for Pawiloma victima.

REFERENCE:

Wilson M. R., J. A. Turner & S. H. McKamey. 2009. Sharpshooter Leafhoppers of the World (Hemiptera: Cicadellidae subfamily Cicadellinae). Amgueddfa Cymru – National Museum Wales. Available online at http://naturalhistory.museumwales.ac.uk/Sharpshooters [accessed:  8 March 2012 ].

Tucuras, langostas, y saltamontes

/ Ted C. MacRae / 10 Comments

Staleochlora viridicata | Cordoba Province, Argentina (March 2011)

Tucuras, langostas, and saltamontes are names in Argentina for what we in North America call grasshoppers (order Orthoptera, superfamily Acridoidea). Argentina certainly has its share of species, some of which can only be described as “gigantes”! During my first week out in the field at my home base here in western Buenos Aires Province, I encountered the hefty-bodied female in the photo below and was immediately reminded of a similar-looking individual I had photographed in neighboring Córodoba Province during my March 2011 visit. Both had short but well-developed wing pads that at first suggested they might be mature nymphs of an incredibly large species. However, when I noted both were females I decided they likely represented adults of some type of lubber grasshopper (family Romaleidae), many of which—especially the females—are brachypterous (short-winged) and heavy-bodied as adults. A little searching revealed that both belong to the genus Elaeochlora, each looking very much like the species pictured on an Argentine postal stamp and identified as E. viridis (update 9 Mar 2012 – Sam Heads has identified these as Staleochlora viridicata).

Staleochlora viridicata| Buenos Aires Province, Argentina (March 2012)

Getting at least a genus name for these individuals then prompted me to go back to photographs I had taken last year of other types of grasshoppers. One of these, Eutropidacris cristata, is truly one of the largest grasshoppers I have ever seen (update 9 Mar 12 – Sam Heads notes that Eutropidacris is now a synonym of Tropidacris). This individual was seen in a soybean field in the northern Argentina province of Chaco. These insects, known in Argentina as “La tucura quebrachera,” apparently occur in outbreak numbers periodically and, understandably owing to their monstrous size, generate a lot of attention. In Brazil the sepcies is known as “gafanhoto-do-coqueiro” (coconut tree grasshopper),

Tropidacris cristata | Chaco Province, Argentina (March 2011)

One of the more colorful grasshoppers I have seen in Argentina is Chromacris speciosa. The individual below was photographed last March in eastern Córdoba Province, also on soybean. It’s tempting to presume that the green and yellow coloration has a cryptic function, but apparently the nymphs of this species are brightly colored red and black and have the habit of aggregating on foliage. This is classic aposematism (warning coloration) to indicate chemical protection from predation, so perhaps there is a similar function to the adult coloration as well.

Chromacris speciosa | Cordoba Province, Argentina (March 2011)

Copyright © Ted C. MacRae 2012

Crazy Eyes 2

/ Ted C. MacRae / 4 Comments

Buenos Aires Province, Argentina | March 2012

While the eyes of this female horse fly (family Tabanidae) aren’t quite as striking as those of Tabanus lineolus (the wonderfully dimorphic males and females of which were made famous by Thomas Shahan and Ralph Holzehthal), they still managed to catch my eye as I was scouting for more pedestrian types of insect in a soybean field in central Argentina this past week. We know this is a female due to the separated eyes (males have larger eyes that meet at the middle of the head—supposedly the better to see females with); and by the obvious, blade-like mouthparts, which the females use to slice mammal skin so they can lap the blood that their eggs need for development prior to being laid while males forego specialized mouthparts and concentrate on using their huge eyes to look for females.

Female horse flies have well-separated eyes and distinct, blade-like mouthparts.

 

I suspect this individual had recently emerged from the soil (where many horse flies pupate) and was still hardening off, as she was very calm sitting on the leaf and allowed me to steady the leaf with one hand as I snapped a few photos with the other. I would have loved to have switched out the 100mm lens I was using and put on my 65mm 1-5X lens to really zoom in on those striking eyes. Unfortunately, I don’t think my field companions shared or understood my fascination with this little insect. If anybody has a clue about the identity of this species please let me know.

Copyright © Ted C. MacRae 2012