I see negative reviews??? Granted not an instant fix but if done correctly this is awesome! First, once you get your order you HAVE TO keep them in a darker place for a few days until you see the little critters moving around. Then put them out.... I have had to wait 10 days once. Also you have to be consistent putting more out at least every month during fly season.Over time it seems the population grows and the flies decrease, until they are under control.I have a small farm so lots of poop, water, and compost around. Plus I live in a place with lots of flies, it took some time but I can go outside without flies all over!This is not for the instant gratification type of customer, but great for someone who wants a long term solution!

I like the price compared to Spaulding and Arbico, and I like the mesh bags provided. However, my second batch never hatched. The box is left out at our gate by the USPS and though I tried to pick them up from out there as soon as I realized they were delivered, we had a heat wave going on and they may have been cooked. Arbico would instruct the post office to hold them for me to pick up there, but Amazon doesn’t give that option. Same would be nice for gel-cap supplements that melt in the heat.

I HATE flies!!! Hate em. I hate the way they sound; the way they look; and the way they are covered in whatever nastiness they're drawn to. Of course there is a time and a place, it's just not in my house or swarming over me while my family is trying to have a meal on the patio.That's why I LOVE these fly predators. I don't have animals or a big manure pile. But that's no reason I can't release 10,000 maggot killing micro-wasps into my yard every few weeks. These little guys really do the trick. Of course they only kill the maggots and you have to work in conjunction with fly traps to get the job done. I also have a Bug-A-Salt on hand to deal with out of town visitors that wander by.Like I said, these do what they claim right out of the package, but after a few months of releases, you're gonna want more. Eventually, like any military organization, you're gonna want an elite unit. That's where I recommend a selection and training process.The selection process is easy: once the wasps start hatching, sequester the first 50-100. These little eager beavers are the strongest and will be your elite force. You'll need to get a mason jar to use as a barracks and an enclosed space for a training area. A spare closet works well. Get yourself some fishing line, some pipe cleaners and some toothpicks. Make the pipe cleaners into circles and other shapes, then suspend them and the toothpicks with the fishing line in your closet. You've just created a fly predator obstacle course.Keep training sessions to no more than 20 minutes with atleast a one hour rest period in between. It'll take some time at first to figure out the best way to get them all back in the jar for their nap, but you'll figure it out. It's not gonna be easy, it'll take some leadership (be firm but fair), but once you get them flying in formation you'll know they're ready. That's when you can promote them from Fly Predators...to Fly Assassins.I know some will say that this is too much effort, but if you've ever sat in your backyard, sipping a cocktail with a squadron of Fly Assassins providing air cover in formation, then you know the value of the time you put in.This is a 5-Star Product!!!UPDATE April 2021: It's that time again. The beginning of fly season starts April/May in Southern California. We begin each season standing at attention while the honor cadet from this year's inaugural class reads the names of the comrades we lost last season. It's very faint and I don't speak Wasp very well so I have to listen carefully, but it's usually pretty poignant. I release in batches of 10,000 so it takes awhile to get through all the names from last year. Luckily, while somber, the troops are always up for a little R&R so after I do a 21 gun salute with the Bug-A-Salt, the wasps usually crack a few beers and I have a glass of scotch to commemorate the fallen. I can't say for sure, but I think the improved morale definitely impacts their effectiveness. Plus they know I care.***On a more general note, I've had 25+ batches of these over the last 4 years and never had one fail. Some batches have taken a lot longer, but as others have said, they need warmth to hatch. I'm not saying other reviews are lying about bad batches, that can happen, but its never happened to me and I wouldn't hesitate to try them if I were you. From the reviews, it seems like the vendor will send a replacement anyway.Yes, they can hatch early and occasionally some can get out of the bag, but not often. They won't harm you if they get in the house but I suggest first opening the box outside to check and then bringing them in to start hatching. It can take awhile. My longest was more than a week after delivery. If you are creeped out and leave them on a porch or in the garage, be very careful with the temperature. Once you see a few I usually wait a day or two before releasing (once I've recruited enough for my elite unit of course). Sometimes I use the bags and other times sprinkle them in areas were the unhatched wasps will be protected for a bit. I also put a few in the trash bins.I hope this helps, and if you are really proud of your Fly Assassin obstacle course, please post pics. I'd love to see and compare notes on training techniques. I heard about a guy in Austin, TX who got his Fly Assassins scuba certified, but I don't have a pool to do underwater training and my kid uses the bathtub every night. Plus, I probably don't have time this year to sew that many micro-wasp wetsuits...maybe my wife will help. Happy Hunting!!!

This is FAR from my 1st experience w these beneficial insects. This year I have had problems with several batches from this establishment (naturesgoodguys). None of the 1st batch hatched. The vendor replaced the order, but not w/o 1st implying that I had no idea how to determine if they had hatched, and in essence told me that they had hatched or would. The replacement didn’t hatch either. I didn’t ask anything further of the vendor, but I did report the failure to them - for THEIR benefit. I ordered another batch – a very small fraction of which did hatch.The insects themselves are very effective, but an insect is unrelated to the concept of a business. And, this is a review is of Naturesgoodguys, not the insect species, itself. Every time that I have communicated w this outfit, even when simply making the effort to provide them with info that could potentially beneficial them (i.e., batch failures) – there response was snippy and accusatory.Today, I ordered a 4th batch because the insects, WHEN they hatch, are effective and I make every possible effort to eliminate flies around my horses. Obviously, the predatory insect aspect of my fly control program is a dismal failure this year - but NOT because I didn't buy any! After I placed my order today, I communicated w the supplier to merely let them know that thus far I have experienced a very high failure rate and I made it clear that I was not asking for anything. Also, in said communication, I stated that I wouldn’t report my concerns publicly b/c I didn’t think that they intentionally sent “eggs” that wouldn’t hatch, but I made that statement BEFORE they once again responded in a rude, snippy, and accusatory tone. They asked where I was placing them whereby - ONCE AGAIN - placing blame for the failure rate on me. Again, I had made it clear that I was not asking for anything. The answer is – I place them in the exact same place that I have ALWAYS placed them. Clearly, these people have absolutely no use for data, which likely contributes to the high failure rate of their “product.” It was too late to cancel my order.I will take my business elsewhere - I certainly couldn't get a worse hatch ratio.