Can. Ent. 101: 164-165 (1969) Newly emerged adults of Dendroctonz~s pseudotmgae Hopkins were separated into pairs of similar size, One beetle from each pair was used as a control; the other was flown on a rotating mill. Soxhlet extractions in petroleum ether revealed that the flown beetles contained significantly less fat.

Most scolytids occupy temporary habitats. Migration, therefore, forms an important part of adult behaviour. Since the extent of migratory movement is positively correlated with the degree of impermanence of the species’ habitat, differences in the behaviour associated with migration must be expected to occur between species. Furthermore, the behaviour of individuals must change in relation to changes in physiology associated with migration and reproduction. These changes have been demonstrated in laboratory studies, and the results suggest that the phenomenon of secondary attraction observed among scolytids may have evolved in conjunction with their utilization of transitory habitats.

The flight of bark beetles covers a short but important period of their life cycle, during which they are exposed to conditions not encountered during the major portion of their life under the bark. The time of flight and the factors which affect it are important, not only to the dispersal and survival of the insect, but also in the interpretation of experimental data dependent upon the beetle's flight activity.Chapman (1954), Rudinsky and Vité (1956), and Atkins (1959, 1960, 1961) studied the flight of the Douglas-fir beetle under laboratory conditions, but there is scant reference to field studies on the flight of this insect. Chapman and Kinghorn (1958) recorded the number caught in window flight traps near Cowichan Lake, B.C., and unpublished reports describe emergence records obtained from cage studies conducted near Lumby, B.C.

The flight capacity (duration and velocity) is an important phase of the flight behaviour of economically significant insects such as the Douglas-fir beetle, because it influences the feasibility of control or preventive measures which might be considered. An understanding of the flight capacity and how it varies in relation to environmental factors is necessary to evaluate the beetles' power of dispersal under different seasonal conditions. This would help to detect new areas of infestation by directing or narrowing the search. It also would help evaluation of the hazard at hand in timber surrounding the infestation and be a further aid in determining the size of areas of sanitation required around the comparatively beetle-free areas needed for special purposes, such as parks.

Can. Ent. 98: 953-991 (1966) T h e behaviour of Dendroctonus pseudotsugae Hopk. in different physiological states was studied in relation to temperature, light, and host.Newly emerged beetles preferred temperatures near the threshold for flight. When conditioned in dry air at room temperature for 16 hours rhey preferred cooler temperatures.At room temperature, most newly emerged beetles settled in the brightest zone of a light gradient (55 foot-candles), although some settled in dimmer zones. If ?he beetles' emergence was delayed or if they were stored after emergence, more remained in the zone between 0.5 and 10 foot-candles.. ln light-darlc tcsrs at room temperature mow newly emerged bectles were photopo~itivc, l~u t some were indifferent and a few were phorr1negtivc. Tncreasing thc temperature and humidity increased the proportion of phoctlnegative individuals. Newly emerged fcnlales oriented mnre directly to a single scwrce of light than males, bur afrer conditioning ur aging both reacted similarly.I-emales were scparated into three behavioural types baser1 on their reactions. Pl~otoposirive indivitlual~ f e w morc readily than indifferent or photoncptive Ijeerler; son~e photonegative females showed no inclination to fly.Photc~positive females were usually host negative hut photmegadve females were hnst positive. l'he proportion of these bchavioural types within different samples variccl: A group cllnr emerged early contained a higher incidence of photopositi\-e !lost-negative individuals than a group that emerged larc, or was .;tored for 10 days aftcr emergence. Rut host-nepativc 1)ectl.e~ \vould arracli log$ after starvation, flight exercise, or exposure to morc attractive hosts.Host-positive females contained less fat than host-negative siblings. The decline in lipids during aging, starvation or flight thus may induce bahavioural changes.There is a co-ordination of successive activities in the Douglas-fir beetle similar to that reported for aphids. The initial urge t o disperse outwcigks responses to host stimuli, but this balancc changes a< the beetle.; fly or as hnsc stimuli increase. The balance between thresholds for dispcnal anti anack also varies in relation to the conditions under n.hicIi the emerging I~eetlcs developcd. Consequently, each individual behaves difl'erently nllen ir emerges. The bchaviour of a population changes as ~h e season progresses and from year to year owing to changes in the state of individuals and in the attractiveness of hosts.