Bug Eric

Carnivorous katydids? That might come as a shock, but in reality, many members of the order Orthoptera, which includes katydids, grasshoppers, and crickets, are omnivorous to at least some degree. This broad diet is one reason these insects are so successful. Let’s take a closer look at one subset of katydids in particular.

A female Orchelimum sp. meadow katydid.

Katydids are also known as longhorned grasshoppers, for their exceptionally long, thread-like antennae, in contrast to true grasshoppers that have shorter, thicker antennae. Katydids are in the family Tettigoniidae. Most katydids are green, brown, or gray in color, though tropical species can be stunningly colorful.

Meadow katydids and conehead katydids form the subfamily Conocephalinae. They are among the most abundant of orthopterans in the eastern United States and adjacent Canada. At this time of year they have reached maturity and are seeking mates. Taking a stroll through tall grass, especially in wetlands, lush meadows, or prairies will flush countless individuals.

A female conehead katdid, Neoconocephalus sp.

A substantial portion of the diet for these katydids is grass seeds, and they have mandibles (jaws) powerful enough to crack them. Conehead katydids are the largest, some members of the gens Neoconocephalus exceeding seven centimeters (nearly three inches). I can tell you from personal experience that you do not want to get bitten by one of them.

A male conehead katydid peers from dense grass.

Meadow katydids and coneheads also feed on forbs, defined as any flowering herbaceous plant that is not a grass, sedge, or rush. The insects feed on the leaves and flowers of those plants.

The impact of katydids on plant communities is not negligible. One study revealed that a population of three meadow katydid species turned nearly 16% of the biomass of a rush species (Juncus) into katydid biomass (Parsons and de la Cruz, 1980).. Damage to seeds developing in flowers resulted in a 30-50% decrease in in seed production of rushes and grasses, too.

A female lesser meadow katydid, Conocephalus sp., feeds herself a grass seed.

Watching a katydid eat is a delightful experience. They are surprisingly nimble, and will use their front tarsi (the “feet” on their front legs) like hands to direct the morsel into their mouths. It is very much like any mammal feeding itself, using its paws.

A male Orchelimum eating an acanoloniid planthopper.

Plant matter has relatively little protein and fat, so those compounds need to come from elsewhere for a katydid to prosper. Consequently, some species, especially the meadow katydids, have evolved to become opportunistic predators on other insects, especially if those insects are injured.

The insects usually encountered by katydids are other species that are herbivorous in the same habitats occupied by the katydids. This includes leafhoppers, planthoppers, and even smaller katydids.

A female Orchelimum feeding on a female smaller meadow katydid, Conocephalus sp. The victim had just mated.

Female katydids need extra protein to nourish the development of eggs, and they get a surprising assist from males. During copulation, the male delivers a sperm packet called a spermatophore. The spermatophore consists of the sperm container (ampulla) and a gelatinous mass called a spermatophylax. This is an expensive gift for the male to produce, but it is less likely that a female will mate again once she is provided this nutritious investment. This is especially true for larger meadow katydids, genus Orchelimum.

The spermatophylax consists of protein, water, some carbohydrates, but few lipids (fatty acids). The female consumes this after mating occurs, along with the rest of the spermatorphore, which protrudes from her genital tract after its insertion by the male.

A pair of meadow katydids, Orchelimum sp., just beginning to mate.

The spermatophore is perhaps one step away from sacrificing yourself entirely to your mate. Science weighs the concrete costs and benefits of such transactions, but perhaps something more meaningful is lost in the translation. The more we learn about the insect nervous system, the shorter the distance between “them” and “us.”

The jelly-like spermatophore forming where the pair are joined.

Sources:Gwynne, Darryl T. 2001. Katydids and Bush-Crickets: Reproductive Behavior and Evolution of the Tettigoniidae. Ithaca: Cornell University Press (Comstock Publishing Associates). 317 pp.
Parsons, K.A., and A.A. de la Cruz. 1980. “Energy flow and grazing behavior of conocephaline grasshoppers in a Juncus roemerianus marsh,” Ecology 61: 1045-1050.
Thornhill, Randy and John Alcock. 1983. The Evolution of Insect Mating Systems. Cambridge: Harvard University Press. 547 pp.

As is the case at least fifty percent of the time, we owe this post to my sharp-eyed partner, Heidi Eaton, who noticed a clutch of eggs laid by a true bug. Upon further inspection, she saw a tiny wasp meandering through the ova. The micro-wasp was indeed an egg parasitoid, in the family Eupelmidae, probably genus Anastatus. The drama took place in a glade habitat at Graham Cave State Park in north-central Missouri, USA, yesterday.

Measuring a host egg with her antennae.

Among the unique features of eupelmids in the subfamily Eupelminae are drastic sexual dimorphism, and stupendous leaping ability, as described in this edited passage by Gary Gibson on Bugguide:

Because of modifications to increase jumping ability the flight apparatus and consequently the ability of female eupelmines to fly has apparently been reduced. …One common name that was suggested for the group was "back-rolling wonders" because the jumps are so powerful [that the insects] tend to tumble on landing. Females prefer not to fly and will simply walk around until disturbed. Males, however, fly as readily as any other chalcidoid. It is possible that females were modified for jumping to enhance [their] ability to escape rapidly from predators such as ants and spiders….The jumping mechanism of females is….unlike other insects which use muscles inserted directly onto the legs to power jumping, Instead, very large dorso-longitudinal muscles in the thorax are used. When these muscles contract the thorax contorts, which changes a longitudinal force of action into a vertical force of action to power the middle legs for jumping. A result of this is that females often die in a U-like posture.

Dead female eupelmid in U-shaped posture after contraction of the jumping muscles

The energy for this instant athleticism is stored in large blacks of resilin, an elastic, rubber-like protein found in many jumping insects. What triggers the flood of energy is unknown, but it causes the muscles to contract, making the thorax suddenly shorter, which in turn pulls the basal segment of the middle leg inwards along a tendon-like muscle. A large spur on the tip of the tibia of the middle leg gives it purchase as it kicks off of the substrate (leaf, twig, or other surface).

There are approximately eighteen known species in the genus Anastatus in North America north of Mexico, and about 160 species globally. All have females with a distinct pattern of bands on the forewing, thought to enhance their mimicry of ants. The wings adhere close to the body when the insect is not flying, to the degree that at first glance the tiny wasps look to be wingless. The ovipositor is almost entirely concealed, which helps separate this genus from similar-looking genera.

Laying her egg inside the host egg.

At least two species have been introduced to this continent, one purposefully, the other accidentally. A. disparis was imported to aid in the control of the Spongy Moth (formerly known as the Gypsy Moth). A. tenuipes apparently arrived with its host, the Brown-banded Cockroach. The species we observed at Graham Cave was clearly one hosted by a true bug, likely in the family Coreidae (leaf-footed bugs). The female wasp inserts a single egg into the host egg, and her larval offspring will be an internal parasitoid of the developing host, ultimately killing it.

Wheel Bug eggs and newly-emerged nymphs.

Interestingly, earlier in the month, while at Fountain Creek Nature Center in Fountain, Colorado, I happened to notice an Anastatus female suspiciously close to a batch of hatching Wheel Bug eggs discovered by another member of our party. There is a eupelmid, Anastatus reduvii, that is a known parasite of Wheel Bug ova, so perhaps that was the unknown suspect.

Fleeing the scene of the crime? Female eupelmid suspiciously close to the Wheel Bug eggs.

Encountering parasitoid behavior in the field is a rather rare occurrence. Rearing the eggs of insects, especially those you can associate with an adult female insect, can add to our collective understanding of host-parasitoid relationships, and even result in the discovery of species new to science. In the case of Anastatus, many species are known only from females. In other cases, males are rare, and/or have not yet been associated with the conspecific females. We clearly have a lot to learn.

Sources: Burks, B.D. 1967. “The North American Species of Anastatus Motschulsky (Hymenoptera, Eupelmidae),” Trans. Amer. Ent. Soc. 93(4):423-432.
Universal Chalcidoidea Database
Eaton, Eric R. 2021. Wasps: The Astonishing Diversity of a Misunderstood Insect. Princeton, New Jersey: Princeton University Press. 256 pp.
Goulet, Henri and John T. Huber, editors. 1993. Hymenoptera of the World: An identification guide to families. Ottawa: Agriculture Canada. 668 pp.

It has been difficult to build-up enthusiasm this summer because insect abundance is way down here in Colorado Springs, but when I get to witness an event like I did yesterday, it makes me glad I went out and made an effort.

Female Ammophila sp. with heavy load

I happened to glimpse a very odd, fairly large insect out of the corner of my eye. It took me a minute to realize it was not a single insect, but two: a female Ammophila sp. thread-waisted wasp toting a caterpillar she had paralyzed. She was trying to locate the concealed nest burrow she had excavated before going hunting, and was wandering around rather aimlessly, but at high speed.

At one point she cached the caterpillar so she could orient herself without such a burden. It worked. She found her burrow, then went back and got the caterpillar. I was lucky to get any images of the transport because she moved so speedily and kept going in and out of focus. Even an attempt at video may have been almost useless. Her agility, with such a heavy load, was impressive. It would be like you or me running at full speed carrying a sofa between our legs.

Removing the "door" to her burrow

She abruptly dropped the caterpillar, and in a matter of seconds uncorked the stone plugging her nest burrow. She quickly entered her burrow, turned around inside, and re-emerged to grab the caterpillar and pull it in. She has to be this fast to avoid tiny parasites known as "satellite flies" that will lay tiny maggots on the caterpillar before the wasp can get it secured underground. Indeed, there was at least one miltogrammine fly flitting at the entrance to the burrow.

Pulling the caterpillar into her burrow

About a minute or so passed with both the wasp and her caterpillar underground. Finally, she emerged topside and quickly retrieved the stone that had plugged the burrow opening previously. She replaced the stone and began kicking sand on top of it. Notice how she curls her front "feet" to maximize the tarsal rake of spines that aid her in digging and filling. At one point she was startled by a curious ant and took to the air for a spit second. Ants can raid wasp burrows and cart off the caterpillar and wasp egg as food for their own young back at the colony.

Replacing the "door" to her burrow

By now I was getting a bit stiff from having stood in the same place for a long while. When I left the wasp, she was apparently unsatisfied with the nest closure and was actively chewing down to the rock plug. I left her in peace to finish what she had started.

Kicking sand to conceal the entrance

The whole sequence of events involved in the provisioning of a nest by a solitary wasp is truly remarkable. She has to dig her burrow and, load after load, flies off with armfuls of soil to fling across the landscape, lest some predator or parasite recognize her nest from piles of "tumulous" around the opening. Next, she fills in the burrow entrance, obliterating all evidence of any cavity whatsoever. She may make a brief orientation flight and then go off to hunt. How does she ever find the burrow again? We cannot even remember where we parked our car, or left our cell phone, and we reportedly have much larger brains than wasps do.

Startled by an ant

Once she has completed her mission of providing one paralyzed caterpillar for a single offspring, she goes off to start the process all over again, somewhere else. Does the wasp immediately forget about the burrow she just completed? How does that instinct work? It has to be plastic enough to address unique situations and overcome obstacles.

Up and away for good?

Over the coming months, in that underground cell, a wasp larva will hatch from the egg and begin consuming its still-living but inactive larder. Scientists believe that insects have no pain receptors, so that must be a blessing to the caterpillar. Were it deceased, though, the caterpillar would quickly rot under the assault of bacteria and fungi. After consuming the caterpillar, the wasp larva enters the pupa stage, as equally inert as the caterpillar on the outside, but inside the pupa there is a massive reorganization of cells converting the grub-like larva in to a sleek, winged adult wasp. Some genes are turned on, others are turned off. It is amazing to contemplate that a wasp larva, or caterpillar, has inside it the latent ability to execute all the behaviors of the adult. It somehow "knows" it cannot fly, does not need flower nectar, and cannot reproduce as a larva. It understands at some fundamental level that its only job is to eat and grow.

Some finishing touches

The next time you are out hiking, and a wasp flies up from under your feet, stop for a second. Back up a little. Does the wasp return to the vicinity? If so, keep watching. She is probably in the process of working on a nest burrow and will resume her activities if you stand still. It takes a little practice just to think about this possibility, but the rewards can be astonishing.

The insect world is full of drama, one of the major attractions for entomologists and naturalists and wildlife photographers. Among the more rarely-witnessed phenomena are raids by slave-making ants in the genus Polyergus, known as "Amazon ants."

Raiding party of Polyergus montivagus

I have had the privilege of seeing three separate slave raids while living here in Colorado Springs, Colorado. All have taken place in late afternoon or early evening. The latest was on July 1 of this year when my wife and I were hiking a trail in Cheyenne Mountain State Park. She happened to pause at what I initially dismissed as yet another harvester ant trail, worker ants bustling about with grass seeds.

Amazon ant workers carrying pupae of their "slaves"

The ants were actually carrying the pupae of their host, ants in the genus Formica. We traced their apparent destination to a Formica colony, but I have learned that this makes sense. The adult slaves on the receiving end of this raid represent members of a colony taken over by an Amazon queen that managed to dupe the workers of an existing Formica colony before killing its queen. Those workers will now set about rearing these most recent arrivals, "adopted" larvae and pupae.

Those jaws are ready for battle

The anatomy of Amazon ant females is such that they are obligatory warriors. Their bodies are sleek and shiny, their slick exoskeletons deflecting the attempted bites of their victims. The jaws of Amazon ants are sickle-shaped and designed to do only one thing well: pierce the heads of the worker Formica ants. Amazons cannot feed themselves, let alone excavate a nest, so they must depend on existing subterranean nests of their Formica hosts. The Formica workers at the receiving end of the Polyergus raid were already enslaved!

The efficiency of a Polyergus slave raid is stunning. One wonders if the victimized colony, pilfered of most of its juvenile workers, ever recovers from such devastation. These ant pirates show now mercy, except for the kidnapped larval and pupa offspring, the majority of which they somehow manage to transport without injury. Not that some of these soft-bodied juveniles will not end up as food instead of slaves, mind you.

Worker Amazon, Polyergus mexicanus

How this specialized lifestyle came to be is open to conjecture, though a reasonable theory comes from studies of ant evolution and genetic relationships. There are slave-making species in the genus Formica, some of them obligatory slave-makers, and others facultative. Facultative social parasites are species capable of existing and prospering in the conventional sense, but are also opportunistic slave-makers. It is surmised that Polyergus Amazon ants evolved from the obligatory slave-making Formica species. Indeed, they appear closely related.

An average colony of Polyergus is between 300-500 workers, surrounded by many hundreds of their slaves. Such a colony can include a mix of different Formica species. Raids on Formica colonies are frequent, and so Amazons need a robust population of host colonies that they can draw from.

Carting off the "booty"

The genus Polyergus is holarctic (found throughout the northern hemisphere), but reaches its zenith of diversity in the United States. There are fourteen species in the world, eleven of which are found only in the U.S. Polyergus mexicanus is likely the one I have been seeing here along the Front Range of the Rockies. Ant diversity in general is surprisingly great here in Colorado, so it is easy to assume you are only seeing a few species when in fact there are several.

Keep an eye out for interesting ant behaviors, and try and document them as best as you can. You could shed new light on our collective knowledge of these amazing social insects.

Sources: Anonymous. 2017. "Polyergus,"Antwiki
Holldobler, Bert and E.O. Wilson. 1990. The Ants. Cambridge, Massachusetts: The Belknap Press of Harvard University Press.732 pp.

My neighborhood walk in Colorado Springs the other day, March 25, was like strolling through living confetti at some points. All the local termite colonies were launching swarms of winged males and potential queens (alates as scientists call them). The frail creatures were not ignored by other animals, either, especially ants. Closer inspection of the swarms revealed three species of ants preying on them.

Alate subterranean termites (Reticulitermes sp.) swarming

Termite swarms are not an indication of the impending collapse of your home or any other wooden structure. Yet, that is the first thought that enters the mind of the average person witnessing the spectacle. Such is the power of advertising for pest control companies. Now, a termite swarm inside your home should probably be cause for alarm. Outdoors, subterranean termites like these Reticulitermes sp. are vital to the recycling of decaying wood. They nest in the soil, as their common name suggests, and forage for wood and other dry cellulose in contact with the soil.

The synchronous nature of termite swarms is a marvel. All colonies in a given area need to liberate their reproductive castes at the same time in order to prevent inbreeding, but I have no idea how they "decide" when to do this. The day before we had snow and high winds. The alates issue from the tiniest of cracks in the soil, like toothpaste from the tube, the better to avoid easy detection. Eventually, enough of the insects appear that their gauzy wings reflect the sun and give away their presence. Soldier termites, and workers, too, escort them out and see them off.

Alate termites with workers and soldier (center) escorts

Hundreds, if not thousands, of winged termites begin filling the air. Few will survive the alert eyes and hungry mouths of birds, lizards, and other predators. The early season timing of swarms may in fact be tuned to precede the emergence of reptiles and the arrival of migrant birds. Ants, on the other hand, are already on the prowl.

Worker Formica sp. ant carrying termite prey

Both ants and termites are social insects, so it is fitting they would be deadly enemies and, one would think, well-matched foes. Watching one swarm happen on the edge of a driveway, I began noticing the appearance of worker ants, Formica sp., crossing the driveway. Eventually I saw one toting a winged termite back to the nest. The ant's nest. More ants followed suit.

Pavement ants (Tetramorium caespitum) killing alate termite (bottom) and worker termite (top)

Turning my attention back to where the termites were emerging, I noticed something even more frightening. Tiny "pavement ants," Tetramorium sp., were killing both alates and worker termites right at the termite nest opening. Whereas Formica ants are a bit larger than the termites, the pavement ants were smaller than their prey. How they avoided the menacing jaws of the soldier termites confounds me.

Formica ants near the entrance to their nest, with prey

Just up the street I noticed heavy ant activity originating at the base of a brick-and-mortar mailbox pillar. These were Formica pallidefulva ants, but appeared larger than the other ones I saw previously. It soon became apparent that they were also taking part in the Great Termite Massacre of 2017. Most of them were carrying wingless alates, though.

Ants (Formica pallidefulva) with termite prey

Alate termites, once paired, shed their wings easily. Both pairs of wings have a weak spot that allows the termites to break them off so they can quickly seek cover. The male ("king") termite follows on the heels of his mate (queen) as they form a two-car train in search of a potential nest site. They must do so quickly if they are to avoid the marauding ants.

Dealate queen with her mate trailing her in a "train"

Whether the honey pot ants were taking dealate (wingless reproductives) termites, or just seizing winged individuals and breaking off their wings, remains a mystery. They are certainly easier to transport without those cumbersome wings.

Worker Formica sp. ant carrying termite prey

As I turned the corner to go home, I caught sight of yet another ant, possibly Formica podzolica. It, too, was carrying a defeated termite. The ant seemed at least somewhat disoriented, and I eventually lost track of it in the thick grass at the edge of the curb.

So, termites are both integral to keeping soils fertile with their decomposition activities, and also a bounty for many other organisms that depend on them for food when other insect life is less plentiful. Ants are the lion kings and wolf packs of the macroscopic landscape, keeping termites and other insects from overrunning the planet. The ants are not immune, though, and in my next post we see them on the other end of the predator-prey equation.

Note: Special thanks to James C. Trager for identification of the ant species.

At some point in their career, every entomologist will be asked the question "do insects feel pain?" A surprising amount of research has gone into answering that question or, in some instances, unrelated research has provided insight into that query. My answer to that question has more to do with the person asking it, and as far as I know, that is a unique response.

Questioning the capacity for insects to feel pain says more about the one who intends to inflict it.

As one who interacts with the public more than many entomologists, it has become evident that while some people have no qualms about ending the life of an insect, even advocating extremely inhumane techniques ("Kill it with fire!" is a common reply to someone else's social media request to identify a household insect), there is an increasing tolerance for insects, even in the home. If the creature is unwelcome, there is now often a plea for a non-lethal means of dealing with the uninvited arthropod.

The flipside of this more empathetic response to "bugs" is the question of whether insects feel pain. The obvious, hoped-for answer is "no, they don't." The person asking is then relieved of guilt for harming or killing any insect in the past, present, and future. So, while the new trend is for more people, especially women, to seek humane methods of insect control, many people still look for examples of how insects do not deserve empathy and compassion as a way to vindicate their own behavior towards other organisms.

The bottom line in the question of whether insects feel pain is thus the unspoken question of whether killing insects and spiders falls into the category of cruelty to animals. Legally, it would be difficult to argue that insects, being animals, are exempt from that crime. Obviously, this is not the case, and I do not see that implied public consensus changing anytime soon. Swatting a mosquito could be an act of "self-defense," though, considering the atrocious diseases that those biting flies can transmit.

Ok, so you want a scientific answer? Most entomologists I know resort to the short answer that insects do not have "pain receptors" like higher animals. This means they have no nerve cells devoted to the perception of pain. Insects can sense heat and cold, for example, and various chemical and tactile stimuli, but not pain as we would define it.

Is the wasp feeling no pain while being killed by the spider?

The fact that many insects, and other arthropods, willingly sacrifice limbs and other body parts in order to survive predator attacks is a testament to how apparently immune to pain they can be. A missing leg hardly slows down a grasshopper. Tattered wings rarely encumber a butterfly finishing its mission of mating and procreation.

As a colleague and fellow blogger noted in his own treatment of this question, another important aspect of physical pain is the emotional distress that comes with it. Ascribing human emotions to non-human organisms is known in the scientific community as "anthropomorphism," and is considered a big no-no when attempting to conduct unbiased research and observations. So ingrained is the concept of avoiding anthropomorphism that we now have to question whether the unemotional conclusions we draw in animal behavior studies are really the correct ones. The truth probably lies somewhere in the middle.

The fact that people are asking questions like this that leave open the possibility that insects and other arthropods are sentient beings is a hopeful sign, regardless if that belief is based in reality. We could certainly stand a little more empathy for other living things. Then again, look how we treat other members of our own species.

Source: Ballenger, Joe, 2016. "Do insects feel pain?," Ask an Entomologist.

During the heat of summer, we all perspire. Some insects find that bodily function irresistible. Among them are sweat bees, various flies, and even butterflies. It is believed that the salts, minerals, and other compounds in our sweat are necessary for these insects, and difficult to find elsewhere. While you might assume that any insect landing on you intends to bite or sting, rest assured these insects are harmless.

Female sweat bee, Halictus rubicundus

Solitary and semi-social bees in the family Halictidae are collectively known as "sweat bees" because of their habit of lapping up human sweat with their short "tongues." They may tickle at most, but if you smack one absent-mindedly, it may indeed sting if it is a female bee. Male bees lack stingers.

Two different sweat bees, both Lasioglossum species

Sweat bees come in a variety of sizes and colors, from miniscule brassy Lasioglossum species to brilliant metallic Agapostemon species (and related genera). Members of the genus Halictus are medium-sized and brown or blackish with white bands across the abdomen. Nearly all species nest in the soil, each female excavating her own burrow.

Female sweat bee, Agapostemon sp.

Compounding the problem of recognizing the different insects that seek out your sweat is the fact that many flies in the family Syrphidae are wrongly called "sweat bees" in casual and regional language. Syrphid flies are more properly called "flower flies" here in the U.S. and Canada, and "hover flies" in Europe.

Tiny Toxomerus syrphid flies are often mistaken for sweat bees

Like bees, they can be important pollinators of flowers, but it is in their youth that they are most beneficial. The larvae of many flower flies prey on aphids, which are major crop and garden pests. Thus, the more syrphid flies, the better, even if they do want to drink your perspiration.

Unidentified syrphid fly on my arm, lapping sweat

Plenty of other flies, mostly blow flies (family Calliphoridae), and flesh flies (family Sarcophagidae), will land on us, too. Even some tachinid flies (Tachinidae) will wander around on bare hands and arms. They may not all be there for moisture or salts.

Tachinid fly using me as a lookout post

Some of these flies may be males that are simply using us as convenient perches from which to defend their territory. They will periodically fly off to chase away competing males, or pursue passing females.

Some butterflies are well-known for requiring certain minerals to complete their life cycle. Usually, male butterflies congregate around mud puddles, puddles of urine or piles of scat left by mammals, or even rotting carcasses, where they obtain nutrients that they will pass to females during mating.

Hackberry Emperor butterfly getting salts from animal dung instead of sweat

Males with a higher mineral content are more desirable to females, though how this is determined remains something of a mystery. She puts the transferred chemicals to good use in producing her eggs.

Occasionally, some butterflies will use us as substitutes for their usual mineral resources. I once had a Hackberry Emperor butterfly land on my toe while I was sunbathing in a park in Cincinnati. I had another land right on my sunglasses in a different location in Ohio, but he viewed me as a convenient perch from which to defend his territory.

Female Lasioglossum sweat bee with tongue extended, lapping sweat

Most research into the attractiveness of human sweat to insects has been directed at blood-feeding insects such as mosquitoes and other biting flies. Consequently, there is relatively little known, and much assumed, about the fascination non-biting "bugs" have with our skin pore excretions. One thing scientists can agree on? Don't sweat the sweat bees.

Tiny female Lasioglossum sweat bee on my fingernail

Source: Gibb, Timothy. 2015. "Do Not Confuse Hover Flies with Sweat Bees," Purdue Plant & Pest Diagnostic Laboratory, Purdue Extension, Purdue University.

Unidentified tachinid fly grooming itself on my arm

The other day (Monday, June 6 to be exact) I was exploring Adams Open Space behind the public library in Fountain, Colorado with my wife. I happened to notice a small ichneumon wasp on the underside of a leaf and snapped a couple of images. This was the best one, and I was shocked to see a cluster of eggs beneath the wasp's abdomen. What was going on?

It had been my previous understanding that female ichneumon wasps deposited their eggs on or in their host, as they are parasitic on other kinds of insects (and spiders in some cases). Why was this one laying her eggs in a mass on the surface of foliage?

I posted the picture and posed that question to a Facebook group of world authorities on Hymenoptera, the order of insects to which ichneumons belong. The next morning I got an answer, courtesy of one Sasha Varga, a doctoral student in the Ukraine. First, he offered the genus identification of Polyblastus. That was surprise enough because the overwhelming majority of ichneumon wasps can barely be identified to subfamily from images alone. Thank you, Sasha!

Varga went on to explain that "as I understand, egg remains on the ovipositor after unsuccessful oviposition, but only one and why Polyblastus accumulates several eggs I really don't know." I was simply impressed with Sasha's command of the English language at this point. Ok, so now I at least have some clarified information I can run with.

Wait, Jitte Groothuis added a link to an article that might shed a little additional light. Jitte is likewise a PhD student, at Wageningen University in the Netherlands. Wow, this little observation of mine is circling the globe....

The article cited is entitled "Eggs and Egg Loads of Field-collected Ctenoplematinae (Hymenoptera: Ichneumonidae): Evidence for Phylogenetic Constraints and Life-History Trade-Offs." It is authored by Heather M. Cummins, Robert A. Wharton, and Aubrey M. Colvin, all of Texas A & M University. It was published in 2011 in the Annals of the Entomological Society of America, vol. 104, no. 3, pages 465-475. This sounds like it is over my head, too, so let's investigate together.

Apparently, an understanding of this paper hinges on an understanding of the differences in life histories between various groups of ichneumon wasps. Some ichneumons are "idiobionts," which means that further development of the host insect is arrested at the time it is parasitized by the idiobiont. Typically, a pupa stage is targeted, but sometimes a larva host, and the ichneumon wasp larva is invariably an external parasite. Idiobiont ichneumon wasps are also much more likely to be "generalists" with a wider range of host insects they can expolit.

Other ichneumon wasps are "koinobionts," meaning that the host organism continues its development at least until the wasp larva completes its development, at which time the host often (usually?) dies. Koinobionts can be either external or internal parasites, though the wasp larva is usually attached to the host, never straying to another host or otherwise moving freely away from the host. Koinobionts are also much more likely to be specialized on a narrow range of host species, in contrast to the generalist idiobionts.

Our Polyblastus here is a koinobiont. In its larval stage it is an ectoparasite (external parasite) of sawfly larvae. The adult wasp emerges from the cocoon spun by the host sawfly larva. This makes sense. We even found a female Elm Sawfly, Cimbex americana at the same location on the same day, so we know potential hosts are present.

According to the abstract of the article, the egg loads of female koinobionts like our Polyblastus are "significantly larger" than the egg loads of idiobiont ichneumons, though the eggs themselves are smaller in koinobionts. Unfortunately, an abstract is all I could find online. I will amend this post should I secure a copy of the entire paper. Maybe having so many eggs, our female wasp is forced to carry some of them externally? How does she keep from losing some simply in the course of searching for a host? How does she manage to attach her eggs to the host one at a time (assuming she deposits ova singly)?

Once again, an innocent observation turns into a convoluted and puzzling mystery. That is exactly what I love about entomology, though. It is a science that keeps you in a constant state of awe, forces you to think imaginatively, and challenges your research skills to the maximum.

Sources: Carlson, Bob. 2010. "Tribe Tryphonini," Bugguide.net.
Cummins, Heather M., Robert A. Wharton, and Aubrey M. Colvin. 2011. "Eggs and Egg Loads of Field-collected Ctenoplematinae (Hymenoptera: Ichneumonidae): Evidence for Phylogenetic Constraints and Life-History Trade-Offs," Ann. Entomol. Soc. Am. 104(3): 465-475.
Goulet, Henri and John T. Huber, eds. 1993. Hymenoptera of the World: An identification guide to families. Ottawa, Ontario: Agriculture Canada. 668 pp.