Tachinid fly on lavender. (Photo by Kathy Keatley Garvey)

You notice an egg on your milkweed plant, and watch its life cycle from egg to caterpillar to chrysalis.  Aha, you think, soon I'll be able to see an adult monarch eclose from that chrysalis.

Not so fast.

If a tachinid fly lays eggs in that caterpillar or chrysalis, you'll get several tachinid flies, not a monarch. The fly larvae will eat the host--the caterpillar or chrysalis--from the inside out.

The tachinid fly is a parasitoid, and you can learn all about this parasitoid and many others at the Bohart Museum of Entomology's open house, Parasitoid Palooza, set from 1 to 4 p.m., Saturday, Nov. 18 in Room 1124 of the Academic Surge Building, UC Davis campus. It's free and open to the public and family friendly. A family craft activity is planned.

What's a parasitoid?

"An insect parasitoid is a species whose immatures live off of an insect host, often eating it from the inside out,"  said Tabatha Yang, education and outreach coordinator of the Bohart Museum of Entomology. "It is part of their life cycle and the host generally dies."

Among the presentations or topics:

• Bohart Museum senior museum scientist Steve Heydon, a world authority on Pteromalids, or jewel wasps, a group of tiny parasitoids.
• Entomology PhD student Jessica Gillung who researches the Acroceridae family "a remarkable group of endoparasitoids of spiders."
• Family craft activity is a pop-up card, featuring a monarch chrysalis and a fly, suitable for mailing to friends and family during the holiday season.

There are some 3,450 described species of Pteromalids, found throughout the world and in virtually all habitats. Many are important as biological control agents.

Members of the Acroceridae are "rare and elusive flies lay the eggs on the ground or vegetation, and the little larva is in charge of finding itself a suitable host," Gillung said. "Upon finding the host, the larva enters its body and feeds inside until it's mature to come outside and pupate. They eat everything from the spider; nothing is wasted."

Her dissertation involves "the evolution and systematics of Acroceridae, focusing on understanding host usage patterns and trends in morphological variation."

Tachinid flies, which lay their eggs in caterpillars and chrysalids, will be on display, along with the remains of its hosts. It is used as a biological control agent for some pests. But those who rear monarch butterflies consider it their enemy when it lays eggs in their caterpillars and chrysalids.

The late UC Davis entomologist Richard M. Bohart (1913-2007) researched Strepsiptera, or twisted-wing parasites, for his doctorate in 1938. Both the Bohart Museum and an entire family of Strepsiptera, the Bohartillidae, are named in honor of Professor Bohart.
 
The Bohart Museum, directed by Lynn Kimsey, professor of entomology at UC Davis, houses a global collection of nearly eight million specimens. It is also the home of the seventh largest insect collection in North America, and the California Insect Survey, a storehouse of the insect biodiversity. 
 
Special attractions include a “live” petting zoo, featuring Madagascar hissing cockroaches, walking sticks, praying mantids and tarantulas. Visitors are invited to hold some of the insects and photograph them.  The museum's gift shop, open year around, includes T-shirts, sweatshirts, books, jewelry, posters, insect-collecting equipment and insect-themed candy. 
 
The Bohart Museum holds special open houses throughout the academic year. Its regular hours are from 9 a.m. to noon and 1 to 5 p.m. Mondays through Thursdays. The museum is closed to the public on Fridays, Saturdays and Sundays and on major holidays. Admission is free.

More information on the Bohart Museum is available by contacting (530) 752-0493 or emailing bmuseum@ucdavis.edu or Tabatha Yang at tabyang@ucdavis.edu.

They're hairy. They're bristly. They're attention-getters.

They probably draw more "yecchs!" than most insects. All the more reason to love 'em.

Frankly, the tachinids (family Tachinidae, order Diptera) could never be misidentified as honey bees, as some pollinators such as hover flies, are. And yes, flies can be pollinators.

Entomologists tell us that worldwide, there are more than 8,200 identified species, and more than 1300 species in North America alone. Who knows how many more are out there?

The 2011 State of Observed Species (also called SOS), issued Jan. 18 by the International Institute for Species Exploration, Tempe, Ariz., lists 19,232 newly discovered species. Of that number, more than half--9,738--are insects. Those figures are already out of date. These newly discovered species were identified in 2009, the latest year statistics are available. It "takes up to two years to compile all newly reported species from thousands pf journals published in many languages," the SOS team says.

Check out the report, billed as "A Report Card on Our Knowledge of Earth's Species."

Who knows? If you're crawling around a flower bed, you might just discover a new tachinid.

The parasitic fly (family Tachinidae) never had a chance.

It went from floral visitor to spider prey to spider dinner when it made a single solitary mistake: it inadvertently fell into a sticky web.

Its life-and-death struggle in our back yard did not escape a trio of cellar spiders (family Pholcidae). They rapidly descended on the squirming fly.

This was the first time I've ever seen cellar spiders hunt together. While one wrapped it in silk for future dining pleasure, another administered a fatal bite. The powerful poison paralyzed it. Then one of the bigger spiders tugged the wrapped prey under the lip of our barbecue table. Out of sight.

Bon appetit! Table for three!

It's not easy identifying "what's for dinner" but Martin Hauser, a senior insect biosystematist with the Plant Pest Diagnostics Branch, California Department of Food and Agriculture, said it's definitely a Tachinid fly. There are hundreds of Tachinidae genera, he says, but this one is very likely a Peleteria.

I'm just glad the catch of the day wasn't a honey bee.

It's a curious-looking insect, the tachinid fly.

The first thing you notice are the thick, dark bristles covering its abdomen. By human standards, this insect, about the size of a house fly, is not pretty.  No way, no how.

But there it was, resting on a purple-leaf sand cherry (genus Cistus, rockrose family Cistaceae) in our garden.

As an adult, the tachinid fly nectars on flowers. In its larval stage, it's an internal parasite. The female is known for laying her eggs in Lepidoptera caterpillars and in the larvae of other insects. Hostest with the mostest? 

Lepidoptera is a order that includes butterflies and moths, and if you study them, you're a lepidopterist.

California has more than 400 species of tachinid flies. There's even one species called the "Caterpillar Destroyer" (Lespesia archippivora). It targets the caterpillars of those graceful Monarch butterflies we see flitting through the flowers. 

Most folks will look at a tachinid fly and mutter "Yecch! That sure is a weird-looking fly."

Sure is.

By human standards.