By Kathy Feagan
Parasitoid (or parasitic) wasps, order Hymenoptera, has a population estimated to be in the hundreds of thousands. They lay their eggs inside other insects in order to feed and birth their young. Their eggs hatch and then feed on the living, paralyzed prey. One exception is the Fig Wasp, Blastopjaga psenes, which are essential pollinators of many fig varieties. They lay their eggs inside galls in Caprifig flowers of fig trees.
Tarantula Hawk Wasps, Pompilidae, are quite sizeable, growing to about 2 to 2-1/5” long and have blue-black bodies and orange wings. They are one of the largest wasps and the state insect of New Mexico. Although they rarely sting people unless threatened, they do have one of the most excruciating stings of any insect! They are found on every continent except Antarctica. The Tarantula Hawk female searches for a host tarantula while carrying hundreds of eggs. A Tarantula Hawk taps, thrums and lays webbing at the tarantula’s burrow entrance (imitating a male tarantula ready to mate) to lure the tarantula outside. After a bit of battling, she then stings the tarantula between its legs, which completely paralyzes it. Then, the Tarantula Hawk drags it to her burrow and lays a single egg upon the tarantula’s abdomen. She then seals the burrow and hunts for more prey for her eggs. When the larvae hatches, it eats a hole in the tarantula’s abdomen, then enters and begins to feed inside the tarantula. The tarantula stays alive, but paralyzed, as the larvae doesn’t eat the internal organs until they are ready to emerge as an adult wasp. The female has long legs with hooked claws making grabbing and pulling their prey easier. Females have a curl at the end of their antennae while males have straight antennae. Only female Tarantula Hawks have a stinger. Males’ only role is to fertilize females. The wasp’s fertilized eggs produce females, while the unfertilized eggs become males. Both male and female hawks feed on nectar milkweeds, other flowers, mesquite and soapberry trees.
Ichneumon wasps (Ichneumonidae, order Hymenoptera) are very slender with longer antennae than other wasps. Females have a very long ovipositor (a wire like appendage at the tip of the abdomen for laying eggs). The antennae have at least 16 segments. They are varied in size from 1/8” long to nearly 5” long, including the ovipositor. Their wings are usually blue or brown. They paralyze pests like white grubs, armyworms, cabbage loopers, fall webworms, tent caterpillars, tomato fruit worms, red humped caterpillars, cutworms and corn earworms. They tap their antennae – males listening for females and females searching for larvae to lay her eggs on. Once she finds a host, by finding the host’s food source, the female then searches with her antennae, which detect vibrations of the prey feeding. She then lays her egg, boring with her long ovipositor, near or inside the body of the host. Once she lays her egg, she flies away. Once her egg hatches, the larvae feed externally on, or bore inside the body of, the prey. Some examples are: Bathyplectes anurus and Bathyplectes curculionis who prey on alfalfa weevils. Colluria coxator feed on wheat stem sawflies. Didegoma inular feed on diamondback moths. Eribus terebrans prey on European corn borers. Hyposoter feed on cutworms and loopers. Patracloides mantanus prey on Cabbage loopers. Icheumonids are extremely beneficial for natural pest control and have been used as biologic control agents. Adults feed on the body of the host insect while the larvae feed on the host’s larvae and pupae.
Here is more information about two of these Ichneumon wasps which are very beneficial. Bathyplectes anurus and B. curculionis (Hymenoptera: Ichneumonidae) parasitize alfalfa weevil larvae by laying one egg into the weevil in the spring. The egg matures to larvae and remains inside the weevil until the weevil spins a cocoon. The larvae then eat the weevil, slowly killing it, and emerge to spin their own cocoon for pupation. Both species of Bathyplectes are very similar. The alfalfa weevil they prey upon has one generation a year and are in larvae stage in the spring, maturing and emerging in early summer. Alfalfa weevils are considered to be serious pests of alfalfa and Chinese milk vetch. The adult Bathyplectes species take flight during the spring stage of the alfalfa weevil’s larvae. Bathyplectes anurus is considered a very effective biocontrol against alfalfa weevils. It is reported that the wasp’s success lies in the cocooned larvae’s ability to jump and roll inside the cocoon to protect themselves from ants, sunlight and heat. When the larvae twitches or jumps, the entire cocoon moves about 2”, then lands and rolls until it finds an ideal, safer spot. Their cocoon is quite porous letting light and ventilation inside. These parasitic wasps are considered extremely beneficial in protecting alfalfa.
Braconid wasps (Cotesia congreatus)have coloration in shades of black to browns to yellows with red to orange abdomens, very narrow waists, and 4 transparent wings. They feed on hornworm and other caterpillars. They usually have a dark spot on their forewings. They are found in gardens and meadows, where butterflies and moths are common. These are very small wasps–less than ½”–with long antennae and ant-like heads. The have a long ovipositor but do not sting people. They lay their eggs on soft caterpillars, especially tomato hornworms, tobacco hornworms, cabbage worms and other pests. They are attracted to the scent of caterpillars eating leaves using the wasp’s astounding sense of smell. Females can lay up to 200 eggs each day in summer. The adult wasps eat the pollen and nectar of flowers, especially flowers and herbs with small flowers. Other species in the Bracconidae family feed on caterpillars, aphids, beetles, squash bugs, stink bugs, and many other pests, laying their eggs externally or internally on the prey – using them to feed their eggs/larvae. A female uses her ovipositor to lay her eggs just under the skin of the prey. As the eggs hatch, the larvae feed inside the prey until they mature, then eat their way out. Once the future wasps are outside, they pupate, spinning tiny cocoons that look like eggs along the back and sides of the prey worm or caterpillar. When adult wasps emerge from the cocoons, the prey usually dies. These are considered mostly very beneficial insects. Bracconidae are the second largest family in the order Hymenoptera with over 17,000 species. Due to their uniquely fantastic sense of smell, some species of these wasps have been trained for detecting narcotics and explosives.
Gall wasps (Hymenoptera: Cynipidae) There are over 1,200 gall wasp species, most using Oak trees as hosts; others using chestnut and fruit trees, hawkweeds, roses and berries. They are tiny, ranging from .0078 to 0.196”. They create galls on Oak leaves but can also be found on the root, acorns, and stems and on the stems and leaves of roses and berries. The wasps are black or purple, narrow waisted, small and stout. They have clear wings with a few veins. They have one sexual and one asexual generation each year. After the wasp lays her egg on an oak leaf, a gall forms which contains one or more larvae feeding inside it. Once the larvae finish eating and maturing, they emerge from the gall. The galls do not seriously harm the oak tree and are kept under control by other parasites, insects and fungi that also live in the gall. Other examples of gall wasps: Oak-apple galls produce large growths with a thin shell in which a single larva grows. Horned galls are usually on oak twigs. Spikey horns come out of the gall and a single gall wasp larva develops in each “horn”. Gouty oak galls create galls that are similar looking to the horned gall but have a smooth surface; these galls are also inhabited by larvae.
Another example of a gall wasp is Fig Wasps, which are extremely beneficial. Fig trees have no flowers on the outside. Figs are pollinated at the stem of a syconium (inflorescence), which is a large, fleshy, hollow receptacle with ovaries that surround tiny flowers inside. Each seed in a fig was made with one flower. Two species of Fig Wasps pollinate figs native to the U.S. The strangler fig is only pollinated by Pegoscapus mexicanus and the shortleaf fig is only pollinated by Pegoscapus tonduzi. When the female flowers are ready for pollination, the fig emits a scent that attracts only the female wasp species required for that tree. The wasp enters the end of the inflorescence losing most of her antennae and wings in the process. The wasp finds the flowers and lays eggs inside the future seeds to feed their larvae; they also spread pollen left behind from previous pollinations. The pollen allows all the seeds to grow. Then the female wasp dies. Her eggs become grubs growing in a gall inside the fig seeds. When mature, the wingless males emerge first to hunt for females, mating inside her gall. After mating, the male digs an escape hole for the female then dies inside the fig. The females emerge, carrying pollen, fertilized and ready to find the next fig. Worldwide, there are approximately 900 species of fig wasps responsible for pollinating 900 species of figs. Most fig wasps only live a few days and future generations pollinate throughout the year, eternally repeating the process.
The Big Country Master Gardener Association offers several education programs each month. There is a program at 6:00 p.m. on the 1st Tuesday of the month at the South Library Branch in the Mall of Abilene, and the same program is offered again at 10:00 a.m. on the 2nd Friday of the month at the Downtown Library. Watch the BCMGA website and Facebook page for the topics and dates of these monthly programs.
If you have any questions, call the Taylor County Extension Office at 325-672-6048 or email us at mgardeners@yahoo.com. We hope you visit bcmgtx.org for information on all Big Country Master Gardener events, like us on BCMGA Facebook, and check out training presentations on BCMGA YouTube. We are here to help you.
Until next week – Happy Gardening!