This will most likely be the last of the regular updates for this year, coming at the end of some 12 weeks of continuous recording (July 31st will be the 80th night)

As we reach the end of July, just a handful of females remain, quite different from the peak of 88 females way back on June 12th. New females are also now extremely unlikely, after a gradual decline in numbers occurred through weeks 11 and 12.

Three graphs are produced below, showing the daily/nightly female counts throughout 2011, the number of new females per night and at the bottom, a graph showing the number of females (in blue) and the corresponding maximum temperature (in red) from one of two locations where the temperature is taken.

The number of males present on site on June 3rd, was highlighted by an hour long experiment using two artificial lures in close proximity (of two types and at different heights) to attract males. One lure placed directly on the ground in light grass, had attracted a total of 17 males by 23:45h, but the other attracted none. Bearing in mind that just six females were present during our survey of June 3rd, it shows how the number of males present on site, is considerably underestimated.

Before going any further, we must state that we are only using artificial lures to attract males on isolated occasions, so that survey results are not affected. At the moment this is purely to test their efficiency as an attractant. Among the benefits of using lures in the future, are that they could provide information on the height at which males fly, how large an area they cover searching for females and confirming at what temperature the males require for flight.

The larval season produced a surprising set of results, with early numbers well up on previous years. With the extremely cold period of weather in late November and throughout the whole of December 2010, it was always uncertain how successful larval over-wintering would be. But after the last of the remaining snow melted in early January, the remainder of the Winter became relatively mild and dry. March continued the dry theme and it subsequently became obvious that it was worth an early start to our surveys for larvae. This immediately proved successful and produced good numbers of larvae within the two smaller size ranges. Larval growth in late March and through April is clearly shown by the differing ratios of 12-16mm (red) larvae to 17-21mm larvae (blue) in the larval sizes table for 2011 produced below.

By the end of April, we began to notice a drop in numbers. This was thought to be directly linked to the very warm and dry conditions experienced throughout most of the period and consequently low numbers of prey items. As the path became drier (along sections A, B, C and D on the map above), larval numbers dropped off and very few were ever recorded in the middle of the path. Most records came from along one edge of the path with the most vegetation growing alongside. Several visits were also made to check for larvae during the morning and while the path was still largely in shade.

The two graphs below show the huge differences in the number of larva from section D to the three others. Section C provided very few larvae for all of the six weeks we spent surveying this year, whilst there was also a general increase in the number of larvae found in section B.