Overwintering survivorship of pupae of the mimosa web worm, Homadaula anisocentra (Lepidoptera: Plutellidae), in an urban landscape

ABSTRACT. 1. Overwintering survivorship of pupae of the mimosa webworm, Homadaula anisocentra Meyrick (Lepidoptera: Plutellidae), was examined in several urban habitats in central Iowa during the winters of 1981–82, 1982–83 and 1983–84.
2. Survivorship and supercooling point temperatures were determined throughout the winters. Corroborative laboratory studies were conducted during the winter of 1982–83.
3. Minimum ambient temperatures that equalled or were below the supercooling point of the insect, at any time, were lethal.
4. Prolonged cold exposure below 0°C and above the supercooling point resulted in high mortality levels. To quantify this relationship, a concept of minimum-temperature exposure was developed by tabulating the number of degrees that the daily minimum temperature was below 0°C for a given sampling period.
5. Some mimosa webworm pupae were found to overwinter in highly protected sites (2.5–5.0°C warmer than the ambient air temperatures) in the urban environment, resulting in less minimum-temperature exposure and reducing the probability of reaching the lethal supercooling point temperature.     

Vigilance in ursine black and white colobus monkeys (Colobus vellerosus): an examination of the effects of conspecific threat and predation

Vigilance is thought to have evolved as an antipredator defense but, in primates, conspecific threat often better explains this behavior. We examined vigilance in one group of Colobus vellerosus inhabiting the Boabeng‐Fiema Monkey Sanctuary in Ghana. We aimed to (1) describe factors affecting vigilance in this population, and (2) examine the importance of predation avoidance and conspecific threat in explaining vigilance patterns. Because of a male takeover preceding the study, our focal group (B2) consisted of six adult males and three adult females. We collected 490 10‐min focal samples (82 hr) from all adults in the group (N=9) from July to November, 2001. To avoid predators, individuals should be more vigilant (i) with fewer neighbors, and (ii) in areas of the canopy with higher predation risks. Conspecific threats can be divided into extra‐ and intra‐group threats. Extra‐group threats should lead to higher vigilance levels (iii) during intergroup encounters, and (iv) in areas where the home range overlaps with other groups of colobus. Intra‐group threats should lead to greater vigilance (v) in the presence of neighbors and (vi) while feeding or occupying food patches (if resources are limiting). Our results best support the hypothesis that vigilance functions primarily to detect extra‐group, conspecific threats. Individuals were most vigilant during intergroup encounters and in areas of range overlap, and monthly vigilance rates were associated with monthly encounter rates. Individuals tended to scan less in proximity to familiar vs. unfamiliar group mates, suggesting that relationship quality may affect colobus vigilance. Finally, predation pressures or anthropogenic disturbances might have influenced vigilance, as individuals were more vigilant low in the canopy. However, this last result could also be due to the lower visibility because of dense foliage or to the fact that the monkeys have access to fewer escape routes when ranging lower in the canopy. Am. J. Primatol. 71:919–927, 2009. © 2009 Wiley‐Liss, Inc.