Tarantula Hawks

Tarantula Hawk, Pepsis spp.

Tarantulas are the heaviest spider by weight, but that doesn't deter one of its main predators: tarantula hawks. These large wasps, most often referring to the genus Pepsis, look similar with iridescent blue-black bodies and orange or red wings. They are best known for hunting tarantulas, sometimes even seeking them within their burrows, although the technique can differ per species. A tarantula that is caught is paralyze, dragged to a burrow dug earlier by the wasp, and drop in. A tarantula hawk egg is laid on the still paralyzed tarantula which is now destined to become the first meal of the larvae, unless the egg never hatches and the tarantula can recover from the venom. Tarantula hawks are otherwise known to be docile, similar to tarantulas, with a diet primarily of nectar. While their sting is reported to be "traumatically painful" and debilitating, tarantula hawks are not known to show unprovoked aggression towards humans.

Technical Difficulties

A Minnesota summer sunrise.

Unfortunately, some technical difficulties will prevent a post for today, but there should be one on Thursday. Sorry for any inconvenience!

Land of 10,000 Lakes

One of the many lakes of Minnesota. (Click to enlarge)

Minnesota is known as the Land of 10,000 lakes, but truly consists of more: approximately 11,842 lakes. The largest lake, discounting border lakes such as Lake Superior, is Red Lake which is 1,168.7 km² (288,800 acres). The actual geography of Minnesota is largely a result of  glaciation, especially during the Quaternary period from 2 million years ago to the present.

The Laurentian Ice Sheet, where now lies the Hudson Bay, had glaciations named for each geographic region: Nebraskan, Kansan, Illinoisan, and Wisconsin. Markings of these glacial events can still be seen in parts of Minnesota today in the form of striations and grooves within the ground, the irregular hilly deposits from end moraine, the high terrace created by ancient rivers, exposed bedrock, and the finely textured silt of loess found in the prairie soils. It is the geographic history that helps create the beauty and unique lands within the state of Minnesota.

Sweet White Clover

Sweet White Clover, Melilotus alba

Sweet White Clover was originally brought from Eurasia to North America as a forage crop, but it escaped cultivation and quickly spread across the continent. While it is most common in disturbed sites, it can also be found in high grade habitats. In addition, fire disturbances can result in explosive growth of sweet white clover, not only by creating good growing conditions, but by also scarifying and stimulating germination. It can efficiently degrade grassland communities by shading native species as it can grow up to 1.5 m (5 ft) tall. Each plant can produce up to 350,000 seeds which are viable for up to 81 years after storage, but it is unknown with environmental conditions, and of those in storage, only 0.6% were viable. While sweet white clover is visited by honeybees, native solitary bees, wasps, and flies, it can self-pollinate. The tap root may reach depths of 1.2 m (4 ft) within the first year and up to 1.7 m (5.5 ft) within the second year. Many species do consume sweet white clover including deer, elk, livestock,  cottontails, waterfowl, and song birds but grassland bird species richness in nonnative grasslands was lower than native grasslands. Prevention of spreading, establishment of perennial vegetation, herbicides within the first year, and frequent mowing are all methods of controlling sweet white clover with relative success.

Pipevine Swallowtail

Pipevine Swallowtail, Battus philenor 

Pipevine Swallowtails are a species of butterfly found within the southern states and into southern Mexico. They prefer open woodlands and meadows, flying primarily in late spring into summer, but may be found in fall or year round in its far southern range. The adults feed solely on nectar including thistles, azaleas, buckeye, lantana, and lupines.

Eggs of a Pipevine Swallowtail on White-veined Dutchman's Pipe.

The common name comes from the host plant for the caterpillar: pipevines of the Aristolochia family which include wooly pipevine, white veined Dutchman's Pipe, Virginia snakeroot, and California pipevine. The toxic aristolochic acids within the plant are sequestered resulting in both caterpillars and adults to be poisonous. Up to 20 red, circular eggs may be laid on the young, tender shoots of pipevine.

Black phenotype caterpillar of Pipevine Swallowtail in 28°C (82°F).

While the caterpillars may initially feed in groups, they scatter as they grow to feed on the more mature leaves of the pipevine. When they are ready to pupate, they find somewhere a ways away from their host plant. The caterpillars are black with red projections and spots along the back, but they are affected by temperatures resulting in shading from black to red as it warms.

Red phenotype caterpillar of Pipevine Swallowtail in 40°C (104°F) weather.

Typically, black caterpillars are found in the southeast and California while red caterpillars are more common in western Texas and Arizona. The presence of the red phenotype increases in other areas as the growing season progress and daily temperatures increase, especially at temperatures above 30°C (86°F). Caterpillar found in Texas were specifically found to be more tolerant of higher temperatures than those found in other regions, specifically California.

Diaspores

Foxtail (Diaspore)

There are numerous types of seed dispersal methods within the plant kingdom. One such method is through a diaspore, a unit that consists of seed and additional tissue to help with dispersal. While these may be found with fruit, common in plants dispersed by frugivores, another commonly seen diaspore is known as foxtail, or spear grass. As the common name implies, it can be harmful, or even fatal, to livestock and pets due to its sharp structure. Foxtail itself refers to a number of grasses, some with a fanning structure and others with a cone shape. Control of foxtail is important in pastures.

Hoverflies

Hoverfly, Syrphidae

Hoverflies are true flies, Diptera, belonging to the family Syrphidae, and with another common name of flower flies. While many have similar coloration to bees and wasps, they have only a single pair of wings which cannot fold similar to a bee when still. There are 813 known species within North America, and near 6,000 species known worldwide. Overall, hoverflies mainly feed on the nectar and pollen of various plants as adults, but act as predators while dull green, legless larvae. They play an extremely important role as aphid predators while larvae, rivaled only by ladybird beetles and lacewings. It is reported they may control between 70-100% of an aphid population when there are plentiful hoverfly larvae. In addition, hoverflies are also known to be important pollinators. They are mainly active during spring and summer, but in the warmer states can be found all year.

Field Bindweed

Field bindweed, Convolvulus arvensis

A member of the morning glory family, Convolvulacae, field bindweed is the bane of many gardeners and states. The perennial was introduced from Eurasia in the late 1800s and has since become one of the most difficult noxious weeds to remove. Field bindweed has an extensive root system which is its main propagation method. The roots may reach depths of up to 6 m (20 ft) which makes hand pulling ineffective and requires multiple applications of herbicides over years for a higher chance of eradication. It is highly drought tolerant and the seeds are viable for up to twenty years with some reports of sixty years. In addition to being a strong competitor against native plants, bindweed will climb and twine around other plants, potentially choking them out of the area.


Time to get back to posting! The next handful of posts will be things I ran across while in Minnesota. Unfortunately, though it is the Land of 10,000 lakes, my time there was limited almost exclusively to work, but I managed to gather a few nature-related photographs for sharing.