Month: May 2014

Turbo Testudine

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gopher tortoise (Gopherus polyphemus)

Gopher tortoise (Gopherus polyphemus) | Tattnall Co., Georgia

Last weekend I traveled to Georgia with two field companions to look for insects associated with sand scrub habitats in the southeastern part of the state. Of course, while I am an entomologist with beetles as a focus, I am also a naturalist who keeps an eye out for all manner of critters, plants, and other natural features. Thus, when we saw an enormous tortoise about to cross the road while driving through sand scrub habitat south of Riedsville, there was no debating whether we should stop and take a look. We immediately recognized him as a gopher tortoise (Gopherus polyphemus), even though none of us had actually ever seen a gopher tortoise in person. (I say “him” because the of the fairly long gular projection, which is generally longer in males than in females.)

gopher tortoise (Gopherus polyphemus)

Contrary to popular perception, this tortoise walked rather urgently.

We pulled over about 50 yards further up the road and began hiking back towards the tortoise. As we got closer, he immediately turned and started running (yes, running!) towards us. Seriously. He reminded me of a puppy that had gotten lost and just seen his master! I don’t think I have ever seen something quite like that, and I don’t think I can really explain it, either.

gopher tortoise (Gopherus polyphemus)

He definitely had somewhere in mind that he wanted to go…

Once we got quite close, he turned away and crawled back up onto the road in an attempt to cross to the other side. I had grabbed my big camera, as I did not want to record this encounter with just my iPhone. I also did not want to photograph him on the road surface, so one of my companions picked him up (with gloves on) and brought him back over to the roadside where I began taking photographs on a more natural substrate.

gopher tortoise (Gopherus polyphemus)

…and he wanted to get there quickly.

This was one enormous tortoise—the carapace easily measured 12 inches in length, which I later read is at the upper end of the range for adults of this species. We marveled at his old-man head and thick, powerfully clawed front legs—an obvious adaptation for a digging lifestyle. I almost wish I had borrowed my companion’s gloves and taken advantage of the opportunity to pick him up myself and see how much he weighed. No matter—he was easily the largest testudine that I have ever seen!

gopher tortoise (Gopherus polyphemus)

Who would think a tortoise could be so hard to photograph!

I don’t know where this tortoise was going or why, but I do know that it was, surprisingly, one of the most difficult to photograph subjects I have ever encountered. He was quite capable of moving along at a rather quick pace (tortoise-and-hare fables notwithstanding) and never stopped urgently trying to cross the road. It was difficult to stay low to avoid a “top-down” perspective and still keep in front of him. We moved him to the other side of the road, thinking that might make him happy, but he would then just turn around and try to get back on the road and cross back to where he came from. I decided to just set the camera on autofocus and, with abundance natural light, starting snapping away to play a numbers game. Out of the few dozen or so exposures I got, the ones shown here are all that I kept (the others mostly showing a “bum” leg or two). The first photo at top is my favorite of the bunch.

© Ted C. MacRae 2014

Mrs. Monday Jumper

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Phidippus princeps female | Howell Co., Missouri

Phidippus princeps female | Howell Co., Missouri

In my previous post, Monday Jumper, I featured a photo of a strikingly colored jumping spider (family Salticidae) that apparently represents an adult male Phidippus princeps. Far too skittish to attempt photographing in the field, I placed him in a vial and photographed him later in the hotel room but still only got one photo that was good enough to post. Shortly after gathering him up, I came across another jumping spider that proved far more cooperative for field shots. This was no doubt due in large part to the fact that she had just captured a fat, juicy caterpillar. I find predaceous insects to be far less skittish when they are involved in the act of consuming prey. This not only makes them easier to approach and photograph, but also adds a desirable natural history element to photos that is sometimes missing in “portrait-only” photographs.

Somber coloration, large abdomen, and small carapace contrast distinctly with the male

Somber coloration, large abdomen, and small carapace contrast distinctly with the male

I say “she” because of the classic female characters exhibited—relatively large and rounded abdomen (males tend to have a smaller and more tapered abdomen), smaller carapace, somber coloration, and absence of a “boxing glove” aspect to the pedipalps. Like the male I had just collected, she was on the foliage of an oak sapling, and as I began taking photographs I noticed in the preview screen the brilliant, metallic blue chelicerae that are a hallmark of the large salticid genus Phidippus. I had also presumed the male I had just collected belonged to this same genus based on gestalt, but I could have never imagined that the two individuals actually represented male and female of the very same species. Such appears to be the case, however, as a thorough perusal of the salticid galleries at BugGuide leads me to believe that the individual featured here is the adult female of Phidippus princeps.

Check out those metallic blue chelicerae!

Check out those metallic blue chelicerae!

These photos still may not approach the technical and aesthetic perfection exhibited by master salticid portraitist Thomas Shahan, but I think they do represent an improvement over my first attempt at photographing a feeding female. The first two photos are fine, but the third suffers from the focus being a little too “deep”, which seems to be my most frequent macrophotography mistake on higher mag shots. If you have any tips on how to overcome this particular problem I am all ears!

© Ted C. MacRae 2014

Monday Jumper

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Phidippus pinceps, adult male | Howell Co., Missouri (studio shot).

Phidippus princeps, adult male | Howell Co., Missouri (studio shot).

A couple of weeks ago, shortly after my friend Rich and I began hiking a 9-mile stretch of the North Fork Section of the Ozark Trail in the far southern reaches of Missouri, we encountered this colorful jumping spider (family Salticidae) on the foliage of an oak sapling. He was not at all in the mood to be photographed—dashing persistently from one side of the leaf to the other and finally dropping to the ground as I tried to close in for some shots. So active was the little guy, that even had I managed to get him within the camera’s field of view it would have been nearly impossible to get him properly focused, much less achieve a nice composition. Hoping he would be a little easier to work with in the confines of a hotel “studio”, we coaxed him into a vial with a sprig of foliage and then got him out and placed him on a branch of dogwood flowers (Cornus florida) that evening once we were in our room. Yes—he was easier to work with, but only by the fact that being in a hotel room made it more difficult for him to escape! He was just as active as in the field, darting from flower to flower in his persistent efforts to elude the large glass eye that kept trying to look at him. For many subjects, I would have given up rather than spend an inordinate amount of time trying to get photographs that likely would not turn out to be what I wanted. But this spider was just so attractive—red and black and white with flashy blue chelicerae! I persisted in my efforts, got about two dozen shots off before he finally did escape, then promptly deleted all but five immediately after seeing them on the computer. The photo shown here is the only “keeper” that I can actually bring myself to post—the focus is a bit too deep, but not so much that it detracts greatly from what is otherwise a fairly decent composition. The more I shoot jumping spiders, the more I am amazed at the portraits that Thomas Shahan achieves with these delightful little arachnids.

After browsing through the salticid galleries at BugGuide, I am inclined to believe this is the species Phidippus princeps, with the coloration and white-stripes on the pedipalps suggesting it is an adult male. ID correction welcome.

© Ted C. MacRae 2014

One-shot Wednesday: pale green assassin bug

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Zelus luridus (pale green assassin bug) | Howell Co., Missouri.

Zelus luridus (pale green assassin bug) | Howell Co., Missouri.

As my friend Rich and I set out a week ago Sunday on the final stretch in our quest to hike the 350-mile Ozark Trail in its entirety, I saw this slender, green assassin bug (family Reduviidae) sitting on a tender young leaf of an oak sapling. I already had my camera out but had outfitted with the 65-mm, 1–5× macro lens in anticipation of small beetles that I wanted to photograph on dogwood flowers. Nevertheless, it was still a bit on the cool side, making me think I might yet succeed in getting off some super-closeup shots of this delicate predator. I managed to carefully snip the leaf from the sapling and move the bug up close to the camera for a nice, blue-sky background shot, but one shot is all I got—as soon as the shutter clicked the bug took flight and left me with this single photo. As I have observed to usually be the case, the body of this individual is thickly covered with debris, which I take to be pollen from the abundant oaks at the height of their flowering period.

I’ve seen this species regularly over the years during my springtime forays in upland, oak-hickory Ozark forests. I presume the species is Zelus luridus, based on an online synopsis of the genus Zelus in eastern North America. As true bugs go, assassin bugs are undeniably cool—sometimes large, often colorful, and pure predators! Interestingly, these bugs have adopted a rather diverse array of strategies to assist their predaceous habits, mostly involving modifications of the front legs. Some involve a more typical raptorial design (similar to mantids) with chelate surfaces or even spines on the femora and tibiae, while others have developed flexible, cushion-like structures on the tips of the tibiae to aid in prey handling (Weirauch 2006). Gross morphological modifications, however, are not the only strategy employed by assassin bugs—some groups use secretions either to paralyze or immobilize their prey. Species in the genus Zelus employ the latter strategy—essentially using their front legs as “sticky traps”. The sticky substance is derived from glands on the front legs and is used to coat numerous, microscopically branched setae on the legs called “sundew setae” in reference to the similarity of appearance and function with insectivorous sundew plants. Interestingly, sundew setae have also been found on other parts of the body, at least in first-instar Z. luridus nymphs, leading to speculation that they may also serve some other function besides prey capture. Perhaps these setae explain why most individuals I see are so debris-covered, as with the pollen-laden individual above.

REFERENCE:

Weirauch, C. 2006. Observations on the sticky trap predator Zelus luridus Stål (Heteroptera, Reduviidae, Harpactorinae), with the description of a novel gland associated with the female genitalia. Denisia 19, zugleich Kataloge der OÖ. Landesmuseen
Neue Serie 50:1169–1180 [pdf].

© Ted C. MacRae 2014

Baby box turtle on white

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Box turtles of the genus Terrapene are extraordinarily common in Missouri, especially in the eastern and southern forested regions of the state where the three-toed box turtle (T. carolina triunguis)—Missouri’s state reptile—is the most commonly encountered form. Despite this abundance and the author’s more than a half-century spent scrabbling through the sticks of Missouri, I have never encountered a youngster as tiny as the one shown in this post (shell length about 2 inches). In fact, I didn’t even find it—my daughter rescued it from our dog, who had found it crossing the gravel driveway at our family’s cabin west of St. Louis. Such overwhelming cuteness demanded a photo session, and rather than deal with the active little hatchling’s persistent efforts to duck into the leaf litter I decided to photograph it on a clean, white background and arrange some of the photos in a “Naskreckian” collage. My daughter wanted to keep the little guy, but eventually she agreed that it would be better off released back into the forest. While it may lead a more perilous life in the forest, the opportunity to dine on fresh earthworms and strawberries should make up for it, and from these photos my daughter can always remember it for the little pup it once was.

Box-turtle-collage_1080x1407

Copyright © Ted C. MacRae 2014

“Picudo negro” (black weevil) on soybean in Argentina

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During my recent tour of soybean fields in Argentina, I traveled north to Tucumán Province and met with entomologists at the Estación Experimental Agroindustrial Obispo Columbre (“Obispo Columbre Agricultural Experiment Station”). This provincial station, established more than 100 years ago (1909), conducts research on agricultural and production technology for the Tucumán agricultural region. Focus crops include sugarcane, citrus, and grain—primarily soybean, corn, wheat, and dry beans, with research activities ranging from basic biological studies on emerging pests (such as Rhyssomatus subtilis, featured here) and Helicoverpa armigera (recently discovered in Brazil and now in northern Argentina) to resistance monitoring for transgenic crop target pests such as Spodoptera frugiperda, Helicoverpa zea, and Diatraea saccharalis.

Rhysommatus subtilis is a significant regional pest of soybean in Tucumán Province.

Figure 1. Rhysommatus subtilis is a significant regional pest of soybean in Tucumán Province.

In recent years the laboratory has had a dedicated effort to characterize the biology and economic impact of R. subtilis on soybean (Fig. 1). Although practically limited to soybean growing regions in Tucumán Province, this insect has increased greatly in importance within that area in recent years along with two other weevils: Sternechus subsignatus (picudo grande, or “big weevil”) and Promecops carinicollis (picudo chico, or “little weevil”) (Casmús et al. 2010). Of the three species, S. subsignatus is perhaps the most serious because of its stem boring habit that can result in stand loss, while P. carinicollis is the least because its feeding is largely limited to leaves. Rhyssomatus subtilis is intermediate in importance, primarily due to larval feeding within developing pods.

Adults feed by clipping leaf petioles. The impact is minor, but it is a characteristic sign of adult presence.

Figure 2. Adults feed by clipping leaf petioles. The impact is minor but signals adult presence.

I have not yet seen S. subsignatus in soybean fields in the area, but I saw P. carinicollis during last year’s tour (see this post) and encountered R. subtilis at several locations during this year’s tour. Rhyssomatus subtilis presence in soybean can be detected even before the adults are noticed by the occurrence of clipped leaflets (Fig. 2), which is caused by adults feeding on leaf petioles.

Adult females chew a small hole into the wall of the developing pod, not to feed but for oviposition

Figure 3. Adult females chew small holes into developing pods, not to feed but for oviposition.

Leaf feeding has little if any impact on the crop; however, as the crop enters pod development stages of growth adult females begin chewing small holes in the pod walls (Fig. 3), not for feeding but for oviposition. Eggs are laid singly in the pod (Fig. 4), with larvae (Fig. 5) feeding on the developing seeds within.

Eggs are laid singly inside the pod.

Figure 4. Eggs are laid singly inside the pod.

This manner of feeding by the larva not only directly impacts yield but also hampers efforts to control active infestations by preventing contact with foliar-applied insecticides. Eventually the larvae mature, exit the pod, and drop to the soil where they burrow, pupate, and emerge as adults during the next cropping season while plants are still in early to mid-vegetative stages of growth.

This neonate larva has just hatched and will feed within the pod on developing seeds.

Figure 5. This neonate larva has just hatched and will feed within the pod on developing seeds.

Management techniques include rotation with grass crops to reduce populations (the weevil is oligophagous on soybean and dry beans), use of insecticide seed treatments to control adults during early vegetative stages of growth, and subsequent use of foliar insecticide applications if adults remain after the effect of seed treatments begins to diminish.

REFERENCE:

Casmús, A., M. G. Socías, L. Cazado, G. Gastaminza, C. Prado, E. Escobar, A. Rovati, E. Willink, M. Devani & R. Avila. 2010. El picudo negro de la vaina de soja en el NOA. Estación Experimental Agroindustrial Obispo Columbre, Tucumán, Argentina, 8 pp.

Copyright © Ted C. MacRae 2014

An arboreal fishing spider

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Last week was my birthday, and as is my usual custom I took the day off in favor of the season’s first “official” bug collecting trip. Falling in late April as it does, my birthday usually coincides nicely with insect activity beginning in earnest here in Missouri, and for this year’s edition I decided to look for Cicindela scutellaris lecontei (Leconte’s Tiger Beetle) on sand prairies in the extreme northeastern corner of the state. Sadly, this year’s unusually protracted spring had resulted in a mostly still-sleeping landscape, and whatever hopes I had of seeing the earliest emerging adults were dashed as thick, gray clouds hung stubbornly in the sky and temperatures refused to edge much above 60°F. Still, a bad day of collecting is better than a good day of just about anything else, and in such situations there are still wintertime collecting methods—peeling bark, cutting wood, breaking stems, etc.—at my disposal.

The "W"-shaped markings on the abdomen with interrupted white borders distinguish this species from the otherwise similar D. scriptus (xxx fishing spider).

Dolomedes tenebrosus (dark fishing spider) | Frost Island Conservation Area, Clark Co., Missouri.

While exploring a sand prairie at Frost Island Conservation Area (Clark Co.), I found a large, dead willow in one of the draws that had apparently been killed by recent prescribed burning activities, and when I peeled back a section of the trunk bark I found this medium-sized spider (leg spread ~40 mm) sitting underneath. Based on general appearance I first thought it was some type of wolf spider, although it struck me odd that it would be under the bark of a tree rather than on the ground where wolf spiders are normally encountered. However, after consulting BugGuide and not finding it among the wolfies, I decided to widen the net and quickly stumbled onto the fishing spiders (genus Dolomedes, family Pisauridae). I’ve seen fishing spiders before—normally they are found at water’s edge and periodically demonstrate a remarkable ability to dash across the surface of the water to grab an errant insect, using the same surface tension for support that had trapped its hapless prey. As odd as it would have been to find a wolf spider high up in a tree, it seemed even more unlikely that I would find a fishing spider in such a dry, arboreal habitat. Things became clearer, however, after I settled on the species D. tenebrosus (dark fishing spider)—distinguished from other fishing spiders by the interrupted white borders behind the “W”-shaped markings on the abdomen (see BugGuide). According to Jacobs (2002) this species is frequently found far away from water, usually in wooded settings, and hibernates as an immature adult (penultimate instar) under—you guessed it—loose bark (also stones). Barnes (2003) also provides a good discussion of this spider along with diagnostic photos and references for further reading.

Dolomedes tenebrosus (dark fishing spider) | Clark Co., Missouri

The “W”-shaped markings on the abdomen with interrupted white borders distinguish this species.

Based on this information, I’m guessing this individual is a still hibernating subadult, presumably a female based on the small pedipalps (the little “legs” next to the mouth). The spider moved slowly across the exposed wood as I took these photographs, wandering onto sections of different color as she did. I like the two photos for different reasons—the first (light background) seems to better show the shape and silhouette of the spider, while the second (dark background) highlights the spider’s beautifully intricate markings.

REFERENCES:

Barnes, J. K. 2003. Dark fishing spider. University of Arkansas Arthropod Museum Notes 15 [full text].

Jacobs, S. 2002. Fishing spider, Dolomedes tenebrosus. PennState College of Agricultural Sciences Insect Fact Sheet [full text].

Copyright © Ted C. MacRae 2014