entomology

Black is beautiful!

/ Ted C. MacRae / Leave a comment

Most species in the genus Crossidius exhibit varying amounts of yellow/red/orange coloration on the body. However, one species—Crossidius ater—dispenses with such adornments and remains all-black throughout its expansive range across the Great Basin and surrounding areas. Despite this, they are no less pretty than their more gaudily colored relatives. The adults in these photos were seen on flowers of yellow rabbitbrush (Chrysothamnus viscidiflorus) at two locations in White Pine County, Nevada on 30 August 2013 (all photos w/ natural sky background).

Crossidius ater | 7.2 mi SW NV318 on US6, White Pine Co., Nevada.

Crossidius ater | 7.2 mi SW NV318 on US6, White Pine Co., Nevada.

Crossidius ater | Ely, 1.2 mi S Jct US6/50/93, White Pine Co., Nevada.

Crossidius ater | Ely, 1.2 mi S Jct US6/50/93, White Pine Co., Nevada.

Crossidius ater | Ely, 1.2 mi S Jct US6/50/93, White Pine Co., Nevada.

Crossidius ater | Ely, 1.2 mi S Jct US6/50/93, White Pine Co., Nevada.

© Ted C. MacRae 2014

Why I went to Georgia

/ Ted C. MacRae / 4 Comments

Call me biased, but for my money few groups of beetles can match the maddening combination of beauty and difficult taxonomy of jewel beetles (family Buprestidae) (I can already hear the protestations of weevil and scarab workers). In the case of jewel beetles, much of the difficulty is due to a propensity for hyperdiverse genera. For example, in North and Central America more than half of the nearly 2,000 described species belong to just three genera—Acmaeodera, Chrysobothris, and Agrilus. It’s enough to make many a casual coleopterist throw their hands in the air and ship their specimens off to “specialists” for identification. This is, strangely, for me part of their attraction. Any reasonably serious effort to study jewel beetles over a period of time is sure to uncover a wealth of new data, from previously unknown hosts associations and distributions to the alpha taxonomist’s raison d’être—new species!

Chrysobothris seminole

Chrysobothris seminole on its host, Chrysoma pauciflosculosa.

One of the more problematic jewel beetle groups is the “Chrysobothris femorata species-group”. For many years, these abundant and conspicuous members of forest and landscape ecosystems have confounded collectors, foresters, and extension entomologists alike. A recent revision of the group by Stan Wellso and Gary Manley (Wellso & Manley 2007) has done much to improve the situation through the description of several new species and clarification of the hosts, distributions, and identifying characters of previously known species. I have benefited more than many from their work, since during the 25 years leading up to that work I had collected large numbers of specimens assignable to this group and was fortunate to have this material examined by Stan and Gary and included in the type series of most of the new species they described. Having in my collection series of nearly all of the known species in this group greatly facilitates identification of specimens received for identification and the recognition of any new species that might come my way. Notice, however, that I said “nearly” all of the known species—there were two species described in that work that I did not have examples of; C. seminole from Georgia and Florida and C. mescalero from New Mexico and west Texas. Happily, I can now say that only C. mescalero is still missing from my collection.

Chrysomoa pausiflosculosa

Chrysomoa pausiflosculosa (woody goldenrod) | Emanuel Co., Georgia.

Chrysobothris seminole is unique in the group by its association not with deciduous hardwood trees, but rather the stems and root crowns of living woody goldenrod (Chrysomoa pauciflosculosa), a member of the aster family (Asteraceae). This plant is not a true goldenrod (genus Solidago), although they are in the same family, but is named such for the profusion of yellow inflorescences that appear during fall and resemble those of goldenrod. However, unlike goldenrod, woody goldenrod is a perennial plant with a woody root crown and stems from which new growth emerges each year. Woody goldenrod is restricted to coastal dunes and sand scrub habitats in the U.S. southeastern coastal plain, although the beetle itself has only been found in a few locations in Florida and southeastern Georgia. The beetle was first collected in numbers by Roy Morris and Edwin Donaldson, who reared adults from woody goldenrod root crowns they had collected in an effort to rear adults of another wood-boring beetle; this one in the family Cerambycidae and also undescribed and restricted to woody goldenrod. That beetle was recently described as Crossidius grahami Morris & Wappes, 2013.

Chrysobothris seminole

Adults are found primarily on lower stems of living plants.

In late May of this year, I made the 13½-hour drive from St. Louis to Emanuel Co., Georgia to visit the type locality of C. seminole and try my hand at finding this species. Along the way I met up with two excellent beetle collectors in Tennessee; Joshua Basham and Nadeer Youssef. Josh and Nadeer are among the few people who have succeeded in collecting this species, having visited the type locality during the previous two years and managing to collect a small series of adults. Their experience proved to be invaluable, as we saw only three individuals during our two days in the area. Josh saw the first soon after we arrived at the type locality and was kind enough to let me see it in situ on its host plant and make the collection, and Nadeer was equally kind to give me the third individual we saw. Our consensus was that a combination of early timing and lack of rain was the reason for their scarcity, and to hedge our bets we collected a number of plants that showed evidence of buprestid (as well as cerambycid) larval workings in the lower stems and root crowns to attempt rearing additional specimens. Because of their scarcity, I kept the adults alive and photographed them later that night in a more secure “studio” setting, and while this species has been photographed before I do believe that the photographs presented here are the only photos of live individuals.

Sand scrub habitat | Emanuel Co., Georgia.

Sand scrub habitat | Emanuel Co., Georgia.

In addition to its unique host plant association and restricted distribution, C. seminole can be distinguished from other members of the C. femorata species-group by both sexes having the frons and clypeus uniformly brown (in most other species of the group the frons and clypeus are variously colored, often brightly so in males of the species). The one other species with both males and females also exhbiting a uniformly brown frons and clypeus is C. mescalero (now the only species still lacking in my collection), which Wellso & Manley (2007) distinguished from C. seminole by having three distinct elytral costae (C. seminole has two indistinct costae), its indistinct elytral foveae (in C. seminole the foveae are distinct), and its southwestern distribution and association with oaks. I suppose now I’ll have to start making plans for a June/July visit to sand dune habitats in New Mexico and west Texas sometime in the near future.

REFERENCES:

Morris, R. F., II & J. E. Wappes. 2013. Description of a new Crossidius LeConte (Coleoptera: Cerambycidae: Cerambycinae: Trachyderini) from southern Georgia with comments on its biology and unusual distribution. Insecta Mundi 0304:1–7 [pdf].

Wellso, S. G. & G. V. Manley. 2007. A revision of the Chrysobothris femorata (Olivier, 1790) species group from North America, north of Mexico (Coleoptera: Buprestidae). Zootaxa 1652:1–26 [abstract].

© Ted C. MacRae 2014

Who likes mole crickets?

/ Ted C. MacRae / 7 Comments
Who likes mole crickets?

Who likes mole crickets?

Scapteriscus borellii

I do!

On a recent collecting trip to southeastern Georgia, we spent the night in Swainsboro. We found a hotel and went to the restaurant across the street for dinner. It was dark by the time we got back to the hotel, and since it was a rather warm, muggy night we did what any entomologist worth his salt would do on such a night—creep around the parking lot and building perimeter checking the lights for insects. Late May is still a tad early for checking lights, but among the small assortment of insects we did find were these slim, active insects known as mole crickets (family Gryllotalpidae). Not true crickets, though related, and certainly not moles, these odd-looking critters are immediately distinguishable by their mole-like, fossorial (digging) front legs—a remarkable example of convergence between members of two completely separate animal phyla.

Scapteriscus borellii (southern mole cricket) | Emanuel Co., Georgia.

Scapteriscus borellii (southern mole cricket) | Emanuel Co., Georgia.

Rather than fiddle with them out in the parking lot, I decided to bring them inside for studio photographs on a clean, white background. The widely separated tibial dactyls (literally, “shin fingers”) of the digging feet identify them as Scapteriscus borellii, or southern mole cricket. Despite their name they are an exotic insect, having originally come from much further south (southern South America) and arriving in the U.S. early in the 20th century. While true crickets jump, mole crickets run—and fast! They also, however, have the comical tendency to play dead for a moment when disturbed before bolting to safety. I was able to use this behavior to my advantage while taking photographs—every time he began running, all I had to do was cover him up with a bottle cap. After only a few seconds I was able to remove the cap and take a shot or two before he got the nerve to try to bolt again.

© Ted C. MacRae 2014

Mrs. Monday Jumper

/ Ted C. MacRae / 4 Comments
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

/ Ted C. MacRae / 1 Comment
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

/ Ted C. MacRae / 2 Comments
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

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

/ Ted C. MacRae / 1 Comment

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

/ Ted C. MacRae / 4 Comments

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