MONMOUTHSHIRE MOTH & BUTTERFLY GROUP NEWSLETTER No 84 June 2012. A monthly newsletter covering Gwent and Monmouthshire Vice County 35 Editor: Martin Anthoney Monmouthshire Microlepidoptera - Changes to the county list since 1994 Sam Bosanquet Following Sam’s article in last month’s issue (No 83) on changes to the VC35 county micromoth list since the publication of Neil Horton’s book (Monmouthshire Lepidoptera, the Butterflies and Moths of Gwent) in 1994, attached to this newsletter as a separate file are details of the 181 micro species added to the list in the 18 years since the book’s publication. Scarce Bordered Straw (Helicoverpa armigera) This immigrant moth occurs in Britain most years but is usually scarce, though 300 were recorded in 1996. One of our members, Bob Roome, recalls his encounters with Scarce Bordered Straw in Africa:- I was introduced to the species in Botswana in 1968, as part of an Overseas Development Administration entomologist team from the Centre for Overseas Pest Research (London). As my first job, I accompanied two experienced entomologists charged with surveying the insect pests of crops in Botswana, carrying out research into their biology and control and advising farmers. We were effectively the first entomologists in the country and quickly set up the beginnings of a national collection in our new research station. Despite being a semi-arid country, merging into the Kalahari Desert, Botswana had a rich insect fauna. “Scarce Bordered Straw” was certainly not scarce where we worked. From the survey, it was clear that the “American Bollworm”, as H. armigera was known, was a major pest. Its larvae damaged the main staple, sorghum, and also maize, cowpeas and the potential cash-crop, cotton. A large Robinson-type trap was made locally for us and was run nightly at the research station near Gaborone, the new capital. Twenty pest or potential pest species were sorted and recorded from the catch daily and the catch was also a source of many other insects for the collection. Specimens were sent regularly to specialists at the Natural History Museum in London for identification or confirmation. The trap had a drum about 1metre in diameter and about 40-45cm deep. On nights during the rains when termite reproductives flew, it would be full to the brim with a chewed-up mass of unrecognisable insect bodies. I was fortunate to be given the task of studying the biology of American Bollworm while my team- mates concentrated on chemical control and advice to farmers. The moth lays its eggs on plants where the flowers are just opening so that the larvae can feed on flowers, developing fruits and seeds. The eggs are laid singly or in small groups and are followed by six larval instars, each becoming significantly larger and more damaging to their host-plant. Mature larvae leave the plant and pupate in the soil below. Many wild plants acted as hosts, especially members of the Leguminosae and Malvaceae. Sampling suggested populations could reach tens of thousands of larvae per hectare in natural bush land and hundreds of thousands per hectare on crops. Five or six generations a year could be achieved. Larvae maturing in May, at the end of the rains and the 1 cropping season, produced diapause pupae that delayed their development until September. The first rains usually occurred in October and there was evidence from a network of light-traps in Botswana, Mozambique, Angola, Zambia and South Africa that weather movements brought in migrant moths from the north. Crops planted on the first rains were more lightly attacked than those planted in December or January which would mature in April and May. H. armigera larva on maize H. armigera egg on cotton leaf Hymenopterous and Dipterous parasites of egg, larval and pupal stages were present and identified. They were less common on natural hosts, but there predators such as birds, small mammals, ants and beetles were probably much more effective than they would be in crops. Egg parasites are the most effective in protecting a crop because of their early effect. Levels of egg parasitism of 80% were recorded in late crops which must have reduced damage and the subsequent over-wintering population of the bollworm. However, in general, parasites rarely prevented serious damage. The moth larvae were susceptible to a Nuclear Polyhedrosis Virus. Infected larvae would be found hanging from the plant as fragile, blackened bags of fluid, their internal organs completely dissolved. The “virus” can be seen under a light microscope in samples of this fluid as very numerous, shiny, polyhedral particles - actually protein structures in which are embedded the much smaller, real virus particles. By using an artificial diet, we reared large numbers of larvae, infected them and produced large amounts of the virus and carried out field trials, using it like an insecticide, which showed considerable promise as a method of control. Experiments using controlled temperature and day-length cabinets enabled us to determine the optimum day lengths to induce the pupal diapause. The optimum, not surprisingly, coincided pretty well with the shortest day lengths in Botswana of around 11 to 12 hours in May and June. Winter rain was extremely rare, temperatures could fall close to zero at night and so pupae had to survive between three and four months of very cold, very dry conditions. Female moths from the main light-trap were preserved for measurements such as wing length and dissected for the presence of spermathecae. Moths caught early in the season were smaller than those caught after December. Most females were virgins though those inseminated could contain as many as 5 spermathecae each. Females trapped in newly-flowering crops were usually inseminated whereas those from maturing crops were almost invariably virgins. Observations made early in the night, in crops, revealed males and females actively feeding, often on honeydew, and females ovipositing. Males “called” to caged, virgin females arrived coincident with minimum temperature, maximum humidity and dewfall which occurred late in the night. Females could be seen releasing pheromone earlier so this suggested pheromone reception was best at dewfall. Scarce Bordered Straw is an old friend (foe?) which provided me with a golden opportunity to do what I enjoy - studying the biology of an insect. As I write this, the rain is rattling down on the skylight of my house. My light-trap this morning contained one, lone example of White-shouldered House Moth, very small, my first ever, but hardly something to shout about, though still better than the previous two completely empty attempts. 2 April has been grim and May starts little better. I hold out little hope of seeing Scarce Bordered Straw this summer - but, who knows! Records for VC35 show it first recorded by Sam Bosanquet in 2003, then by Roger James and Martin in 2005, with more than 16 recorded widely in 2006 and only one since (Martin 2011).Our catches must depend on a coincidence of successful breeding on the continent and North Africa with suitable weather movements to bring them to our shores. Global warming plus the increased planting of sweet-corn may make Scarce Bordered Straw more than just a very occasional breeder in the U.K. The “Scarce” in its name could become something of an anachronism. Bob Roome in Botswana Scarce Bordered Straw (Helicoverpa armigera) Bob Roome Recent Highlights Record amounts of rainfall, cool temperatures and strong winds – can this past month really have been June? It is looking increasingly likely that a misbehaving Jet Stream will limit summer to ten days at the end of May. It is no great surprise that numbers of Lepidoptera, particularly butterflies, have been very poor this month. 30th May One Small Eggar larval web south of Saltmarsh Farm, Uskmouth. Second instar, so they are late this year. (Kevin Dupé) 15 Small Pearl-bordered Fritillary, 20 Dingy Skipper and 25 Small Heath at Blaenserchan (Rupert Perkins) 31st May Another Small Eggar web at Goldcliff (Kevin Dupé) 1st June Grass Rivulet and a remarkable fourteen Sharp-angled Carpets amongst 38 species at Penallt (Stephanie Tyler) 2nd June Cypress Carpet to light at Undy, the first of four individuals at this site during June (Keith Jones) 3rd June Eyed Hawk at Marine St., Cwm, Ebbw Vale (Jeff Smith per Tom Eyles) 3 4th June A single Painted Lady at Llandegfedd Reservoir (north end) (Steve Williams) 6th June Cream-spot Tiger at Uskmouth (Kevin Dupé) Another Cream-spot Tiger and Small Yellow Underwing at Magor Marsh (Simon Phipps) Cream-spot Tiger 7th June Beautiful Snout at Llandogo (Simon Phipps) Satin Lutestring and Lime Hawk at Risca (Martin Anthoney) 8th June Little Thorn at Llandogo (Simon Phipps) Grass Rivulet, Six-spot Burnet and Burnet Companion at New Grove Meadows (Simon Phipps) 9th June Small Pearl-bordered Fritillary at Silent Valley Reserve (Tom Eyles) 10th June Green Hairstreak at Blaenserchan (Rupert Perkins) 11th June Oblique Carpet and Obscure Wainscot at Goldcliff (Kevin Dupé) Scarlet Tiger and Fern at Llandogo (Simon Phipps) 12th June Small Yellow Underwing, Grass Rivulet and Six-spot Burnet at Springdale Farm (Simon Phipps) 13th June 3 Small Pearl-bordered Fritillary at Blackrock Quarry, Clydach, and 3 more adjacent to Whistle Road car Park, Blaenavon (Martin Anthoney) Cypress Carpet, Scarlet Tiger at Undy (Keith Jones) 16th June An immigrant Bordered Straw to light at Risca (Martin Anthoney) 18th June Dark Green Fritillary, Small Pearl-bordered Fritillary and Dingy Skipper at Blaenserchan (Rupert Perkins) 4 19th June A late, worn, Dingy Skipper at Wyllie (Martin Anthoney) At least four Forester moths flying at Flatwood Meadows, Crosskeys. The first record of this UK Priority species at the site for eight years (Martin Anthoney and Roger James) Small Seraphim Forester Moth 22nd June Blackneck the best of a mere eight macro species at our National Moth Night event at Newport Wetlands as NMN lived up to its reputation for bad weather (MMBG).