Monday, July 18, 2016

Cicada Killers or Cicada Hawks

A female Cicada Killer attempts to carry off her prey.

     Eastern Cicada Killers (Sphecius speciosus) are large, solitary wasps that go by several other common names: Cicada Hawks, Sand Hornets, and Giant Digger Wasps for example. They are in the family Crabronidae, which has 4 species in North America and 22 world wide, all specializing in preying on cicadas. Their scientific name translates to "Wasp" and "showy" respectively.
     They certainly do stand out. They're big, up to 2 inches for females around here. Though solitary, males will form territories around good nesting habitat, guarding what are called leks, or breeding grounds. Since they buzz loudly and fly up to investigate anything flying through their territories, they can be quite intimidating. They grapple mid air, sometimes crashing to the ground while engaged with one another, scaring people in the vicinity in the process. Here's a short video of a male guarding a hole, waiting for an available female to stop by:


     Recall however that stingers on bees, ants, and wasps are modified ovipositors, used for egg laying. Since males do not lay eggs, they cannot sting. They do have what amounts to hard tip on the end of their bodies though, a pseudo stinger that can poke, but again, this is all bluff.
     Here's a look at some cicada killers mating: 

     Females Cicada Killers can sting, but almost never do. Researchers have had to hold them in place to illicit stings, and supposedly the stings are no worse than a pin prick. They would only sting if caught by hand, stepped on barefoot, or got trapped in clothing. Walking or mowing over them will not aggravate them into stinging.
     Many people confuse Cicada Killers with the large, introduced European Hornet. These large yellowjacket-like wasps are capable of nasty stings. Since they also hunt large insects, seeming to like to eat cicadas as well, they are often called cicada killers when indeed they're not.

A European (German) Hornet attacks a Cicada. They're often confused with Cicada Killers. A smaller Yellowjacket hovers overhead.

     Female Cicada Killers require a cicada for their young to develop. They hunt for them, stinging them until they're paralyzed. Although you'd think they catch more male cicadas who are singing and advertising their presence than females, they seem to get an equal number of each. They go after the various species of "annual cicadas" (those that come out every year, but whose individuals may spend several years feeding underground). The Periodical 13 and 17 year cicadas have evolved to emerge earlier and are done breeding by the time Cicada Killers usually emerge. After stinging a cicada, they carry their prey back to their burrows. Since the weight of a cicada, especially the larger females, is 2-3 times the weight of a female Cicada Killer, that is no easy task. Here's a short video from the Capital Naturalist YouTube Channel showing one attempting to do so:


     Cicada Killer burrows average about 6 inches deep, but can go deeper than 2 feet. The females excavate them using their jaws to loosen the soil and then pushing the dirt back out the holes using modified spines on their legs. This means that they are very picky about where they build their nests. They like to choose bare, loose, well drained (often sandy) soil, sunny if possible. Sometimes 2-3 females will share an entrance, but each then digs burrows away from the main tunnel to use as their own chambers.

     Each female has a cell she provisions with the paralyzed cicadas. She leaves one cicada if she decides to lay an unfertilized egg which results in a smaller male Cicada Killer. She will leave 2-3 cicadas if she decides to leave a fertilized egg, resulting in a larger female wasp. Thus the males are smaller, much smaller if they were provisioned with a small male cicada. Eggs are placed under the second pair of legs of the paralyzed cicada. Females sleep in the burrows at night.

A lek, or breeding area, full of Cicada Killer burrows.

     After a couple of days, the eggs hatch. The larvae feed for about 2 weeks, feeding on the cicada, leaving its vital organs for last so it can stay fresh longer. The young pupate and overwinter in a cocoon, emerging in late June or July of the following year.  All adults die after breeding, none making it past the Fall. Adults nectar at flowers and feed on sap flows, being very minor pollinators.

     Though these huge wasps, among the largest in North America, can be intimidating, they are harmless to people. It is unfortunate that they sometimes choose our lawns, garden beds, window boxes, and playing fields to sometimes build their burrows, but these are beneficial insects. They can be discouraged by mulching or heavily planting the areas they favor, but should just be left alone otherwise. 

Wednesday, July 13, 2016

Eastern (Black) Ratsnakes

     The Eastern Ratsnake (Pantherophis alleghaniensis) is our longest and one of our most commonly seen snakes. Formerly called the Black Ratsnake (Elaphe obsoleta), both it's common and scientific names have been changed and formalized. But many people still refer to it as a Black Rat Snake or simply Black Snake. It is the longest snake in the region, the only one that regularly grows to over 6' in length. The world record is one that measured 101 inches from its snout to its vent. The Virginia record is a 67.3 inch one. Its large size along with ability and tendency to climb trees makes this snakes among the most visible in our area.
     Although the large size of Eastern Ratsnakes may make them seem intimidating, they are harmless to people. They will only bite if threatened or handled, and then only about half the time anyways. They prefer to slither away quickly, sometimes musking the perceived threat with a foul smelling liquid if handled. Eastern Ratsnakes will sometime curl up is an S-shape, hissing, vibrating their tail tips, and striking in an attempt to intimidate the potential predator into leaving it alone. The teeth are relatively small for such a large snake, leaving little pin pricks marks and not really causing any great harm. 
     This is a beneficial creature to have around. As the name suggests, they are superb at controlling rodents, being able to get into their burrows and tackling even large rats, killing their prey by constriction. They are however also opportunists, feeding on whatever is available and small enough for them to eat, including birds, eggs, salamanders, shrews, chipmunks, and sometimes larger prey. Because they are such good climbers, they sometimes get themselves in trouble with people who put up bird boxes that haven't been protected sufficiently, eating the occupants. 

Eastern (Black) Ratsnakes are excellent climbers and are often seen basking in trees.

     But overall, they are great allies and find plenty of rodents in urban areas to satisfy their appetites. They can really gorge themselves when food is plentiful. I once was feeding a large 6'+ ratsnake in a nature center I worked at. I was curious as to how many mice it could eat at one sitting. After 23 mice, I had nothing left to feed it, and it was still looking for more. 

     But ratsnakes can also go long times between meals. They can go months without eating if need be, their cold blooded metabolism being very efficient at not burning up energy reserves. This makes them arguably better at rodent control than other predators such as foxes, owls, hawks, and cats, who not only can't get into the rodent burrows, but also cannot go such long times with out eating, having to either move away or die. Not so with ratsnakes. When the rodents do return, they can resume eating with no real harm to the snakes.
     Luckily many people realize the benefits of having ratsnakes around. Sometimes they're referred to as the "Farmer's Friend" and purposely released into barns and out buildings. Their shiny black coloration, with a bit of white on their chin/neck and partial checkerboard pattern on their bellies helps to distinguish them from some of the other black snakes around. 
     But the young are sometimes confused with other snakes because they differ so much in coloration. They have a blotched pattern along their backs that turns all black as they age. Some people confuse them for other snakes such as copperheads or rattlesnakes (especially since these snakes, like many others, will shake their tails in the leaves and thus sometimes sound like a rattle). One of the best identification features for juvenile ratsnakes is a dark line that crosses the eyes to the mouth, almost like a unibrow. 

A juvenile Eastern (Black) Ratsnake, note the line connecting the eyes and blotched pattern.

     That the young sometimes put on a good show by pretending to be big and bad to scare away dangers sometimes backfires when they encounter people. This use to be a good defense against a predator that wasn't sure if it was dangerous. But now of course this can cause people to be frightened and often ends up with them killing the juvenile snakes. 

     Here's a short video from the Capital Naturalist YouTube Channel that shows you one such display: 

     Eastern Ratsnakes take at least 4 years to reach maturity and breeding age. They lay their eggs (from 5-44 of them depending on the size of the snake) in late June or July around here. They often seek a rotting log or compost pile, the site helping to keep the eggs warm. If the site is a good one, they may use it year after year. The eggs hatch 60-75 days later, with the parents showing no parental care other than finding a good place to hide the eggs and the young are capable of catching their own prey at birth. If nothing eats them, they can live up to 22 years and 11 months, the record so far in captivity. 

     Eastern Ratsnakes overwinter in a dormant state referred to as brumation. Brumation sites (hibernacula) are often used year after year, with some sites containing several snakes. Occasionally they will share the hibernaculum site with other snake species, including venomous ones such as copperheads and rattlesnakes. This has led to the mistaken belief that they can mate with venomous snakes and thus produce the patterned young. This of course is completely false.
     I always am thrilled when I find an Eastern Ratsnake, often still calling it a Black Rat Snake in my excitement. I always try and tell folks about how beneficial they are, try to allay people's fears. I hope that these great and adaptable snakes can live in harmony with us well into the future. This will benefit people, but I also want our younger generations to be thrilled to find a really big snake, like I always am, and be able to talk about them to their kids in the future.

Thursday, July 7, 2016

Hercules Beetles - Rhinos, Unicorns, Oxen and Elephants

     The Eastern Hercules Beetle (Dynstes tityus) is the heaviest beetle in North America. This huge creature (up to almost 3 inches) goes by several other names as well: Rhinoceros Beetle, Unicorn Beetle, Ox Beetle, Horned Beetle, and Elephant Beetle for example, though other beetles are often better known by these names. The scientific Genus name is derived from the Greek for "lord" or "ruler" while the specific epithet refers to a Greek mythological giant Tityus. They certainly are impressive beetles. Members of the same family are also large and have all sorts of horns and projections. I've been lucky enough to come across a particularly large Elephant Beetle (Megasoma elephas) male, a close cousin, among the palm logs in El Salvador.

An Elephant Beetle we found among the fallen palm trunks in El Salvador.

     As large and heavy as they are, these beasts can fly. I remember one evening when I was manning a black light set up to attract moths and other insects. Everything at night seems a bit louder and more ominous, and I was actually a bit startled when I heard a Hercules Beetle come crashing through the bushes and crash into the hanging white bed sheet. It was as though someone had tossed a rock into the cloth.
     Male Hercules Beetles are larger and heavier than the the females. They have impressive horn-like pincers that they use to combat other males. Males often setup their territories on a rotting log (preferring ash trees) near the females which have attracted them using pheromones. They take on all challengers in their pursuit of a mate. They try to push, grab and shove each other off the log, holding on tight with their powerful legs. Whenever I find one, it always surprises me how strong a grip they can have. The largest and strongest males gain the opportunity to mate with any females who choose their logs to lay their eggs in their logs.

An Eastern Hercules Beetle grub and a females adult (note the lack of horns).

     Females lack horns. They lay their eggs into the rotting wood. The grubs that are born get to be huge in the two (sometime three) years it takes them to mature and then pupate. They feed on decaying wood, causing no harm to living trees. Despite the fearsome look of the beetles or grubs, and especially the huge pincers of the males, they are harmless to people.

A male Eastern Hercules Beetle, dark from being well hydrated and freshly emerged from the moist soil. 

     Adult beetles live for several weeks to a few months. They can vary quite a bit in coloration, with fresher and better hydrated beetles often appearing darker than older and more dehydrated ones. When buried in the soil, their shells seem to absorb moisture and darken. They typically have an almost velvety appearance. Adults feed on rotting fruits and sap. I've had fair success feeding them fruits with a bit of molasses on them. They seem to love the molasses and maple syrup that's been watered down just a bit.
     These beetles are always a thrill to find, and we use to have people bring them to the nature center I worked at every year, worried about these insects, and always happy to learn they are harmless and not garden pests. With the loss of mature forests and because they are negatively affected by light pollution that disorients them, they're not as common to find anymore. Their strength and size has resulted in their various common names, but regardless of what people call them, they're always impressed when they do find them.