On Monday, Postmaster General Louis DeJoy will appear before the House of Representatives to discuss the recent rollback of service changes that have been blamed for widespread reports of delayed and lost mail.

The slowdown has affected everything from Amazon deliveries to prescription medications and has prompted concerns related to mail-in balloting in November. But it has been particularly disruptive to a number of businesses that rely on the Postal Service to safely ship something you may not have known, or wanted to know, can be sent through the mail: live animals, including chicks, crickets, lizards, frogs and even scorpions.

For those businesses, a shipping delay is often a literal matter of life and death.

(Full disclosure: I have ordered crickets to feed a pet lizard before. I used FedEx. The delivery was fine. My handling, less fine.)

The Postal Service has over 100 years of experience shipping live animals, starting in 1918 when it began allowing live day-old chicks to be mailed. Newly hatched chicks are uniquely amenable to mailing as they can survive without food or water for 72 hours after hatching, according to a bulletin by the Poultry Welfare Extension, a project of several public universities.

Today, millions of pounds of live poultry get mailed each year, according to the Extension, although exact numbers are not available and representatives from the Postal Service did not respond to requests for comment.

And poultry is just the beginning. The agency also has highly detailed regulations for the safe shipping of bees, adult birds, scorpions and “other small, harmless, coldblooded animals,” from worms to lizards.

Bees, for instance, may not be shipped via air, with the exception of queen bees, who may travel by air “accompanied by up to eight attendant honeybees.”

In addition to chickens, other poultry species that can be shipped when chicks are a day old include “ducks, emus, geese, guinea birds, partridges, pheasants (only during April through August), quail, and turkeys.” Chicks of any species older than 24 hours may not be shipped. Many adult birds, however, can be shipped, provided they weigh between 6 ounces and 25 pounds, which is enormous for a bird — approximately the size of an adult pelican.

All poisonous and venomous animals are prohibited, with the exception of live scorpions, provided those scorpions are intended for use in medical research or the production of antivenin. Scorpions may only be shipped via ground transport, and only in a double container system in which each container layer is clearly marked “Live Scorpions.”

Mammals are prohibited, as are all spiders. Baby alligators are allowed, however, as long as they are under 20 inches long.

“The USPS is our only option,” Tom Watkins, vice president of chicken producer Murray McMurray Hatchery, said in an email. “No other carrier deals with live animals. It stems from chicks, to crickets, or bees and many others,” he added.

Watkins says his operation, based in Webster City, Iowa, has not experienced any delays this summer. “We are not cavalier with the lives we handle, but we have not seen the issues that are being reported,” he said. “We track every box and get daily updates on times. We have 94-95% on time in under two days and 99% in under three. This hasn’t changed at all.”

Watkins’s experience stands in sharp contrast with reports out of Maine, where poultry operations have reported 4,800 dead chicks received in recent weeks, according to the Press Herald, prompting Rep. Chellie Pingree (D-Maine) and colleagues to pen a letter to DeJoy and Agriculture Secretary Sonny Perdue asking for answers.

“Hatcheries in multiple states have reported spending thousands of dollars to refund or replace orders for customers,” the letter says. “The losses have been so significant that some growers have begun driving across state lines to transport chicks from the hatchery to the farm themselves, at significant personal expense.”

Losses aren’t limited to poultry farmers. Darien Drollinger owns DubiaRoaches.com, a business that produces live roaches that are fed to bearded dragons, hedgehogs and other insectivorous animals. The business employs about 50 people and ships 1,000 packages of roaches a day, exclusively by the USPS. That’s created challenges this summer.

“The slowdown has caused a lot of issues in regards to delays and DOA [dead on arrival] orders,” Drollinger said. “In fact, last month we had around $40,000 in replacements we had to send out.”

Nevertheless, the company has been outspoken in its support of the USPS on Facebook, where it has cultivated a following of over 160,000 people. “The Postal Service is mentioned in our constitution, and provides a lot of important services to Americans,” as a recent post put it. “It was never created to be a business, but instead a service to unify the nation.”

Drollinger says that roaches are much cheaper to ship through the USPS than FedEx or UPS, and that the agency’s lengthy history with live animal shipments makes them better suited to the work.

Joshua Willard, who owns Michigan-based Josh’s Frogs, said his company had to stop sending live frogs, insects and other animals through the Postal Service after noticing an “exponential” increase in delays starting early July, resulting in more than half of its shipments ending up late — a potentially disastrous situation when dealing with delicate animals like crested geckos and dart frogs.

Willard said that while low prices are a benefit of using the Postal Service, there’s something less tangible about it as well.

“People usually have better relationships with their postal workers,” Willard said. “Their mailmen realize they’ve got some live stuff so they’ll give the order extra care,” for instance, or the workers at The Post office will call customers to let them know they’ve got a live order waiting.

Another leading insect vendor, cricket farm Fluker Farms, also announced earlier this summer it is suspending USPS shipments. David Fluker, the farm’s second-generation owner, said it wasn’t due to delivery delays necessarily, but rather the unusual heat.

“It was just too hot to ship First Class,” he said. “Our DOA rate with USPS First Class is usually under 2 percent, but because of the heat and shear volume of increased orders it spiked a bit.”

“We intend to resume USPS first class when it cools down a bit,” he added.