On a nature hike at Green Lake on Aug 23rd, we found a strange-looking growth on an oak leaf. It was apple green in colour, and in fact looked something like a small, green apple. About one and a half centimeters in diameter it was soft and pliable to touch. Broken open it revealed what looked like a seed inside suspended to the ‘skin’ by many fibers. My first thought was that it was some kind of fungus - a parasite. But breaking open the ‘seed’ revealed a tiny, translucent grub or larva.

Off to the books and the Internet - and the story was revealed. What we had found was an Oak Apple Gall which the tree had produced in an effort to protect itself from a wasp. The life cycle of this wasp is amazing. In late spring a wingless, female wasp had laid her egg in a bud or in a vein of a new leaf. This had activated the oak to form a protective structure around the egg - the gall. The egg hatched and a larva grew inside this gall.

A couple of months later the larva would develop into a winged adult wasp - either a male or female - and bore its way out of the gall. As males and females from separate galls mate, the empty galls will blacken and shrink. The now fertile females will burrow into the soil at the base of the tree where they will insert eggs into the oak tree’s roots. Here again the tree will produce galls to protect itself - root galls each of which will contain another larva, but one that takes about sixteen months to mature into a wasp.

This wasp will be a wingless female, who will climb up the trunk of the tree and start the process all over again by laying eggs in the buds or leaves. This alternating cycle of male or female winged wasps from leaf galls and wingless females from root galls will continue for generations! Isn’t nature awesome!

This tiny wasp (perhaps a centimeter in length) will not bite. According to some articles the Latin name is Amphibolips confluenta, but others call it Biorhiza pallida, but all the articles referred to it as the Oak Apple Gall Wasp. The wasp only uses the oaks as hosts - the apple part of the name is only indicative of the appearance of the gall.

Now if someone would tell what it was that we found growing on a sumac!

Observations: 

 Charles Mitchell, from Loon Lake, called to describe a large black spider that had built a web on the top of a four-foot maple tree, and was apparently guarding it. This spider is the Dock or Fishing Spider, and one of the Nursery Web Spiders.  She would have placed her egg sac in the protection of this closely-woven web, and will stay and guard it until the young hatch and disperse.  

Share what you have seen, call Jean at 268-2518 or email currawong13@sympatico.ca