While walking through a wood, I saw an acorn with an unusual growth on it (acorn enclosed). What is it?
Serena Dool, Butlerstown, Co Waterford
Recently on a holiday in Devon, I had lunch in a grove of oak trees. Many of the acorns lying around had what looked like a growth on them (acorns enclosed). I wondered if this was caused by an insect.
Bill Kilpatrick, Enniskerry, Co Wicklow
These acorns have been distorted by knopper gall which is caused by a tiny wasp, Andricus quercusalicis. The gall wasp lays an egg in the bud of the developing acorn which triggers this woody growth around the larva. The galls overwinter and the wasps emerge in spring.
This summer there were very few butterflies around, so in mid-August when I noticed some butterfly eggs on a nasturtium plant, I decided to rear them and release them in spring. They took about three days to hatch and a further three weeks to pupate. I expected that they would not emerge until spring. To my astonishment after three further weeks I found six white butterflies in the box.
Nancy O'Flynn, Blackrock, Co Dublin.
It was probably due to the warm weather that this second generation of small white pupae did not overwinter. The generation that was laid in May would have pupated in about three weeks; but the second generation usually overwinter to produce butterflies in spring. Of course some seasons the small white butterfly will produce a third generation. Nasturtium is one of the food plants of its caterpillars.
While hill-walking in Wicklow, just a few miles from Tinahely, I came across a large shallow rainwater pool in which were about 50 very large tadpoles and a few small frogs. The tadpoles were at least twice as large as the frogs. Is it not extremely late in the year for tadpoles, and as tadpoles are cannibalistic, why did they not attack and devour the very small frogs.
David F. Nolan, Santry, Dublin, 9
It can take anything from three months to a year for tadpoles to develop into frogs, depending on the weather (cold inhibits the development) and, as is probable in this case, the food supply. The forelegs appear in tadpoles only a few days before they leave the water, but they are fully developed under the skin and that would make them seem larger than the froglets whose legs are extended. Large tadpoles will eat smaller ones and the meat off dead frogs, but could not manage a live froglet.
Michael Viney welcomes observations sent to him at Thallabawn, Carrowniskey PO, Westport, Co Mayo. email: viney@anu.ie
Observations sent by email should be accompanied by postal address as location is sometimes important to identification or behaviour
A Wildlife Narrative, compiled from 10 years of this column, is available at £9.99 from all good book shops and Irish Times Books fax 353 1 6718446