Natural garden pest control: Ladybugs and praying mantis

I'm fascinated by organic gardening.  One of the perks to growing your own food is knowing exactly what has gone into the soil and onto the foliage of your crops.  Inarguably, one of the benefits of non-organic gardening is effective pest control.  So when I began to see evidence that something was chomping on my baby plants (and not Mrs. Rabbit), I sought out some "natural" pest control from our local gardening store,  Frazee Gardens.

Frazee offers lady bugs and praying mantis to help control your garden pests.  I bought one package of ladybugs and one praying mantis "pod," which looks like a chrysalis.  The ladybug package contained 1500 ladybugs, and the praying mantis pod was said to contain 300 baby praying mantis, waiting to hatch.

I carefully followed the directions on both packages, releasing the ladybugs at dusk and clipping the mantis pod to my vertical garden frame and lattice (see All New Square Foot Gardening: Grow More in Less Space!).  The next morning, I had ladybug carcasses everywhere, and only a few live ones crawling around.  Hmmmm....Back to Frazee I went.  To their credit, they handed over another package of ladybugs without batting an eye, and promised to call their supplier to follow up.

Round two: I released 1500 ladybugs at dusk.  This time, I noticed quite a few dead ones right away.  The package does say it contains 1500 to allow for some attrition, giving a net of approximately 1200 ladybugs.  Fast forward to Sunday morning: dead ladybugs, all around.

So what is killing my ladybugs?  I've mixed the soil that is in my raised bed, so I know it doesn't contain any pesticides that should harm the bugs.  We haven't had the grass surrounding the bed sprayed, so I don't think the bed has been cross-contaminated.

Hypothesis One: It was unusually cold the first night that I released the bugs.  Although late in the spring, we did have a light frost.  Maybe it froze the ladybugs.
Counterpoint One: The ladybugs are kept in a refrigerator prior to purchase to keep them in a dormant state.  A little bit of cold--not a hard freeze, mind you--shouldn't hurt them.

Hypothesis Two:  It has been really rainy.  Maybe it was too wet for the ladybugs.
Counterpoint Two: It didn't rain the night of the first release, and there were dead ladybugs in bag two, even before releasing into the garden.

Hypothesis Three:  Pre-packaged ladybugs are a good idea IN THEORY.

What about the praying mantis pod?  300 baby praying mantis were supposed to hatch out two weeks after the weather reached 72 in the daytime.  We're well into June, and I've got no baby praying mantis.

Hypothesis One: Our unusually cold weather froze them in their pod.  This makes me sad.  I'm imagining 300 little mantises (or is it mantii?) snuggled up in their pod, thinking they are protected from the elements.  Not so, my little dears.

Hypothesis Two:  Our unusually wet weather drowned them.  Now I have floating baby mantis carcasses in their pod.  Ugh.

Conclusion:  It might be my bad luck, it might be weather, it might be poor stock from the distributor, but the ladybugs and praying mantis didn't work in my garden.  If you've had a different experience, please comment and include links to reputable suppliers.  I'd be game to try it again.