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Abstract
Pseudohermenias clausthaliana overwinters in the 3rd or 4th larval instar in a hollowed needle of Norway Spruce, roughly from October ist till April Ist. Within the geographical distribution of the species the larva is exposed to temperatures as low as - 30° C during this period. After emptying of the gut in September, the length of the larva is 5.3 mm ± 0.2, but hereafter it starts diminishing until the length is just 3.2 mm ± 0.2. During the first part of hibernation total weight decreases from 0.89 mg ± 0.06 to 0.68 mg ± 0.08; this drop is due to a loss of 29.5 % of the original water content. Dry-weight increases by as much as about 27.7 %, probably due to binding of about 7 % of the original "free" water content. Dry-weight, expressed as a percentage of the total weight, is I9.6 % ± 2.8 in the autumn and 33.3 % ± 2.5 in the winter. It has been suggested that the increase in dry-weight is caused by hydrolysis of certain organic compounds. Larvae exposed to I00 % R.H. and I8° C for 8 days without food at the beginning of March did not regain the original water content, while active larvae, feeding in the field in April, had regained the original high water content. Larvae at 85 % R.H. and I8° C for 8 days in March lost a little water but survived well, and they probably achieved an equilibrium with the surrounding air. Thus the critical equilibrium humidity seems to be less than 85 % R.H.
Abstract
Nest construction and behaviour in the nest of the female and the larva of Panurgus banksianus was studied. The nest has an excavation gallery and a special tumulus-free entrance. Several laterals are made from the descending gallery, and ten cells were found in one nest. A nest with one cell is completed in one day and the excavation of a new lateral takes about 2 I/2 hours. A new entrance is often tunneled out when 4 or 5 cells have been made in a nest, and the former entrance is then used as an excavation gallery. The cell has a conic, lined neck. During provisioning the female stores the pollen as a loose heap, and the pollen sphere is not formed until about I hour 45 min. after the last provisioning flight. The curved egg is firmly attached with its posterior end on top of the sphere. During the feeding of the larva it gradually glides down to the floor of the cell, but its venter is maintained apposed to the provisions and the anterior towards the cell-closure. The provisions are consumed in about 2 weeks. When the larva starts defecating, the pellets are attached to the wall of the cell. The pupal stage begins about the Ist of June in northern Denmark, lasts about 3 weeks, and the adults spend 3 days in the cell after hatching. An absolute minimum of 8000 host plants per day was required for the I70 ♀♀ of the colony.