Happy 4th of July everyone. I am celebrating by cleaning saguaro cactus fruits today. I have harvested a couple of buckets of them, all off of plants on my property that I either salvaged since 2002, or planted as juveniles 16 years ago, some of which are now tall enough to start reproducing and have borne fruit for their first time ever. (This is as opposed to harvesting fruits from the wild ones on the nearby hillsides, which was what I did before.)

Anyway, the photo shows the stages of saguaro fruit maturity once they turn from purely green (not yet ripe) to fallen to the ground. On the left are fruits that have colored up and are ripe, but not yet open. In the middle are fruits that have just started to split, probably earlier in the day, and are revealing bright red pulp dotted with shiny black seeds the size of small pinheads.

In the middle right are fruits that split open fully, which exposes the pulp to consumption by birds, bats, bees, wasps, and ants, to name a few animals that seek them out. The fruits look like scarlet flowers at this stage, and there is a glut of them flooding the saguaro forest with tens of millions of seeds. They usually remain attached to the tops of the cacti for another day or two, and often the pulp is temporarily unconsumed at this point because there’s just so much of it on every saguaro. This often means that the pulp dries out into a dark, congealed mass much like fruit leather, created by the desert sun and dry air, and sometimes the entire seed mass slips out of the fruit rind and falls to the ground in a sticky clump, where it is readily consumed by terrestrial creatures such as foxes, coyotes, rodents, rabbits, javelina, quail, and especially harvester ants, which might well consume more of the saguaro seeds produced every year than all the other animals combined.

And finally, the fruits on the far right are dry husks that have fallen to the ground and desiccated in the summer heat. These dry rinds are sort of decorative, and often persist for several weeks or even months in this dried state because the rinds are tough and not nearly as edible as the sweet pulp and oily seeds are. But as summer wears on, most rinds will eventually be eaten, primarily by small rodents, since they still represent a decent nutrition source when compared to the usual spare desert offerings.

Lastly, a keen observer will note that there is a small blue caterpillar in the middle of the photo about 3/4 inch long. This is the larva of a nondescript snout moth, probably the blue cactus borer, Cactobrosis fernaldialis. This seldom-seen caterpillar feeds upon various species of cacti, usually upon the flesh of the stems, which they tunnel through unseen for months eating as they go. Small round exit holes can be seen upon the waxy skins of many native cactus species if you closely observe them, although the moths also readily attack non-native cacti in gardens and nurseries. Fortunately a healthy mature plant is not usually terribly damaged by the grubs’ boring activities, although small seedlings or particularly tasty exotic species can be severely weakened or killed. Sometimes however the wounds caused by the tunneling are invaded by bacterial necrosis caused by the pathogen Erwinia cacticida, and that can be fatal. I usually find a few of these blue caterpillars in saguaro fruits upon harvesting a large quantity of them. I am not sure if they actually grew up inside the fruits (I suspect so) or if they come from the main body of the plant and migrate into the fruits (which seems less likely.) Whatever the case, it is a blue caterpillar, which is in itself pretty odd!