Saturday, August 18, 2012

Catalpa Springs

   We have a Catalpa tree growing on the riverbank in our front yard.  We enjoy the Catalpa's giant, heart-shaped leaves and, at times, the leaves' nectar "springs" make for great conversation.
Even the bees love Catalpa leaves... at least this time of year.
extrafloral nectaries on catalpa leaves
  Bees, yellowjackets, wasps, and ants are attracted to the Catalpa leaves because the leaves have extrafloral nectaries which produce nectar on the underside of the leaves.
The extrafloral nectaries are located where the leaf veins meet the midrib.
Extrafloral nectaries on a Catalpa leaf
The extrafloral nectaries are also located at the base of the leaf where the leafstalk branches out.
I like to think of these spots that seep nectar as "springs".

   The Catalpa's nectaries do a good job of attracting a variety of insects. The plan is to provide an attractant for the wasps, bees, etc... and in return, gain some protection against herbivores. In other words, providing "refreshments" for all these predators increases the chances of them finding caterpillars, or other pests on the Catalpa leaves... and with all these hunters milling around, it's more likely the pests will be killed or parasitized.  
 Yellowjackets are the most common visitor to our Catalpa.  We've all seen yellowjackets foraging at a picnic for anything... even grilled chicken.  Yellowjackets love meat... here is a photo of some yellowjackets feeding on a "grilled" dragonfly on my vehicle's grill.
 It follows, that, if there are plenty of these meat-hunting wasps visiting the leaves of the Catalpas, there will be increased chances of them capturing any leaf-munching caterpillars.
    Yellowjackets aren't the only visitors to the Catalpa's nectaries.  I've seen plenty of other kinds of visitors... like this iridescent bee.
I saw numerous ants on the Catalpa leaves.
A number of solitary wasps came to the "sweet spots".
I noticed a Lady Beetle scurrying up the midrib... from one nectar seep to another.
   From the looks of the picture below, even spiders may try to take advantage of the visitor-attracting nectar springs by lying wait nearby... just like they do on flowers
   The way I see it... it's astounding to see the Catalpa tree pit the wasps against the caterpillars.

Sometimes, our backyard entertainment is our Catalpa tree.

1 comment:

  1. extrafloral nectaries -- as I always say Dana, I ALWAYS learn something new on your Blog. Thanks.