<p>This report is a result of a first survey of Halland’s gravel pits as an assignment from the County Administrative Board of Halland. The focus has been on Apalus bimaculatus, since the Swedish Environmental Protection Agency are creating a restoration program as it is red listed as Near Threatened. The purpose was also to get an overview of the pits since the County Administrative Board wants to continue this project. Apalus bimaculatus is easy to overlook since it is a short-lived beetle and it lives early in the spring. The species parasitize on Colletes cunicularius which are dependent on fine-grained, exposed sand in sunlit areas with Salix nearby. Gravel is a limited resource that today is replaced with crushed rock, this is a big problem for the beetles since the gravel pits are their primary habitat. The sand pits have a continuous disturbance which results in mixed sand and removed vegetation. This early succession state benefits species that are sensitive to competition. The after-treatment of the pits disfavors Apalus bimaculatus when plantation of trees occurs and the exposed sand disappears. It is suitable to save sun exposed slopes and to prevent overgrowing of vegetation. The survey was between 5th of March to the 19th of April and in total 96 active and disused pits was visited. The species was found in only two localities but 14 were considered as suitable environments since they contained exposed sand and Salix.</p>

Rapporten är en analys av inventeringsdata på bibagge (Apalus bimaculatus) och vårsidenbi (Colletes cunicularius) från Länsstyrelsen i Västra Götalands län. Naturvårdsverket har utformat ett åtgärdsprogram för bibagge då den är upptagen på rödlistan som nära hotad (NT). Bibaggen är en brandgul skalbagge som man finner i blottade, solexponerade, sandytor där dess värdart vårsidenbiet lever. Bibaggen är nämligen boparasit på vårsidenbiet. Endast under parningstiden, några få veckor i slutet av mars och början av april, är bibaggen aktiv ovan mark. Detta är anledningen till att den för bara några år sedan var en förbisedd art i den svenska skalbaggsfaunan. Idag finns arten främst i grus- och sandtäkter men då man nu övergår till att använda sig av bergkross istället för sand från täkter riskerar dess livsmiljöer att växa igen och försvinna. I rapporten analyseras inventeringsdata med utgångspunkt på att hitta de strukturer i täkterna som styr förekomsten av bibagge och vårsidenbi. Analyserna gjordes med hjälp av regressionsträd, korrelationer och t-test. Resultatet blev som förväntat att den viktigaste förklaringsfaktorn till att det fanns bibaggar i en täkt var att det fanns vårsidenbibon. Vid framtida inventeringar för att finna denna svårinventerade art kan det vara en bra ide att koncentrera sig på att leta efter vårsidenbibon för att på ett effektivare sätt hitta lämpliga lokaler för bibagge. / The report is an analysis of inventory data on apalus bimaculatus and colletes cunicularius from Länsstyrelsen in Västra Götalands County. Naturvårdsverket has designed a program for apalus bimaculatus because it is noted on the red list as near threatened (NT). Apalus bimaculatus is an orange beetle found in bare, sun-exposed, sandy areas where their host species colletes cunicularius live. Apalus bimaculatus live partly as a parasite in the site of colletes cunicularius. Only during the mating season, a few weeks in late March and early April, is apalus bimaculatus active above ground. This is the reason why it was an overlooked species in the Swedish beetle fauna until a few years ago. Today the species mainly live in gravel- and sandpits. Now when the use of gravel and sand decreases in favor to crushed rock the gravel- and sandpits as well as the species’ habitat is at risk to disappear. The report analyzes inventory data trying to find the structures in the pits that govern the existence of apalus bimaculatus and colletes cunicularius. Analyses were by regression trees, correlations and t-test. The most important explanatory factor for the existence of apalus bimaculatus in a pit was the presence of colletes cunicularius. To more efficiently find this difficult inventoried species in future surveys it may be a good idea to concentrate on looking for sites of colletes cunicularius.

This report is a result of a first survey of Halland’s gravel pits as an assignment from the County Administrative Board of Halland. The focus has been on Apalus bimaculatus, since the Swedish Environmental Protection Agency are creating a restoration program as it is red listed as Near Threatened. The purpose was also to get an overview of the pits since the County Administrative Board wants to continue this project. Apalus bimaculatus is easy to overlook since it is a short-lived beetle and it lives early in the spring. The species parasitize on Colletes cunicularius which are dependent on fine-grained, exposed sand in sunlit areas with Salix nearby. Gravel is a limited resource that today is replaced with crushed rock, this is a big problem for the beetles since the gravel pits are their primary habitat. The sand pits have a continuous disturbance which results in mixed sand and removed vegetation. This early succession state benefits species that are sensitive to competition. The after-treatment of the pits disfavors Apalus bimaculatus when plantation of trees occurs and the exposed sand disappears. It is suitable to save sun exposed slopes and to prevent overgrowing of vegetation. The survey was between 5th of March to the 19th of April and in total 96 active and disused pits was visited. The species was found in only two localities but 14 were considered as suitable environments since they contained exposed sand and Salix.

Bibaggen Apalus bimaculatus är en rödlistad skalbagge som förekommer i öppna sandiga miljöer och är starkt knuten till sin värdart vårsidenbi Colletes cunicularius vilken den boparasiterar på. Inventeringar av sekundära habitat i form av sand- och grustäkter har utförts i Västra Götalands län under tidig vår 2009 och 2010. Data från dessa inventeringar har i denna studie används i samband med undersökning av omgivande markslag runt dellokalerna/täkterna för att ta reda på om omgivande markslag påverkar förekomst av bibagge vid dellokaler/täkter. Inom sand- och grustäkterna registrerade inventerarna enskilda dellokaler där fynd av bibagge eller vårsidenbi gjordes. Om ingen av arterna observerades angavs en koordinat där en dellokal ansågs vara mest lämplig för en av arterna eller för båda arterna. I ArcGis skapades en buffertzon runt alla dellokaler med 541 meters radie, vilket baseras på det maximala uppmätta flygavståndet för vårsidenbi vid näringssök, 350 meter, summerat med medelstorleken för täkter i Västra Götalands län, 191 meter. Radien baseras även på ett antagande om att täkterna har formen av en cirkel. I buffertzonerna analyserades sedan hur stor area respektive markslag utgjorde kring respektive dellokal med och utan fynd av bibagge och vårsidenbi. T-test utfördes för att se om arean av olika markslag skiljde sig åt mellan dellokaler med och utan fynd av bibagge och vårsidenbi. Regressionsanalys utfördes för naturliga logaritmen av antalet bibaggar och vårsidenbin vid dellokaler och arean av respektive omgivande markslag. T-testet för medelarea lövskog inom buffertzoner omgivande dellokaler med och utan bibagge är det enda som visar på en statistiskt signifikant skillnad (t=2,36, d.f.= 184, p=0,02). Ett statistiskt signifikant negativt samband kunde vid regressionsanalyserna påvisas för naturliga logaritmen av antalet bibaggar och area åkermark inom buffertzoner (r2 = 0,38, d.f.=14, p = 0,01). Ett statistiskt signifikant positivt samband kunde påvisas vid regressionsanalysen för naturliga logaritmen av antalet bibaggar och area barr- och blandskog inom buffertzoner (r2 = 0,46, d.f.=14, p = 0,004). Resultaten är mycket intressanta, speciellt då de erhållits med hjälp av grov markslagsanalys i GIS. / Apalus bimaculatus is a red-listed beetle that occurs in open sandy habitats and is strongly tied to its host species, Colletes cunicularius, since it parasites on its nest. Inventories of secondary habitats in the form of sand and gravel pits have been performed in Västra Götaland County in early spring 2009 and 2010. Data from this survey have been used in this study to examine if surrounding habitat types influence the occurrence of A. bimaculatus in gravel- and sandpits. Within the sand and gravel pits the surveyors registered different patches where A. bimaculatus or C. cunicularius where found. If none of the species where found the patch which was considered to be most suitable for one or both species where registered. A buffer zone was created around the patches in ArcGis with a radius of 541 meters, which is based on the measured maximum flight distance of C. cunicularius during search for food, 350 meters, together with the average size of sand and gravel pits in Västra Götaland County, 191 meters. The radius is also based on an assumption that the gravel- and sandpits has the shape of a circle. The buffer zones were then analyzed to see how big area each habitat type represented around each respective patch with and without findings of A. bimaculatus and C. cunicularius. T-tests was performed to see if the area of various habitat types differed around patches with and without findings of A. bimaculatus and C. cunicularius. Regression analysis was performed for the natural logarithm of the number of A. bimaculatus and C. cunicularius at patches and the area of respective surrounding habitat types. The t-test for mean deciduous forest area within the buffer zones surrounding patches with and without A. bimaculatus is the only one that show a statistically significant difference (t = 2.36, d.f.=184, p = 0.02). A statistically significant negative relationship was found with the regression analyzes for the natural logarithm of the number of A. bimaculatus and the area of cropland in the buffer zone (r2 = 0.38, d.f. =14, p = 0.01). A positive relationship that was statistically significant was found for the natural logarithm of the number of A. bimaculatus and area of coniferous and mixed forest in the buffer zone (r2 = 0.46, d.f. =14, p = 0.004). The results are very interesting, especially when they are obtained by using rough habitat type analysis in GIS.