Adult pales weevils react to light and temperature cues regarding their movements in pine plantations. They remain at the base of their host trees during the day and move onto the trees after dark. A drop in light intensity to 2 fc triggers this response. Ambient temperature below 10°C curtails their movements. Weevils placed on the ground are photophobic at temperatures below 20°C and photophobic and thermophobic above 35°C. Orientation is erratic above 40°C and heat stupor occurs in a few minutes

Corneil, Jeffrey A

Wilson, Louis F

English

Valparaiso University

The Great Lakes Entomologist Volume 17 Number 4 - Winter 1984 Number 4 - Winter 1984 Article 8 December 1984 Some Light and Temperature Effects on the Behavior of the Adult Pales Weevil, Hylobius Pales (Coleoptera: Curculionidae) Jeffrey A. Corneil Oregon Department of Forestry Louis F. Wilson USDA Forest Service Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Corneil, Jeffrey A. and Wilson, Louis F. 1984. "Some Light and Temperature Effects on the Behavior of the Adult Pales Weevil, Hylobius Pales (Coleoptera: Curculionidae)," The Great Lakes Entomologist, vol 17 (4) Available at: https://scholar.valpo.edu/tgle/vol17/iss4/8 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 1984 THE GREAT LAKES ENTOMOLOGIST 225 SOME LIGHT AND TEMPERATURE EFFECTS ON THE BEHAVIOR OF THE ADULT PALES WEEVIL, HYLOBIUS PALES (COLEOPTERA: CURCULIONIDAE) Jeffrey A. Corneil' and Louis F. Wilson2 ABSTRACT Adult pales weevils react to light and temperature cues regarding their movements in pine plantations. They remain at the base of their host trees during the day and move onto the trees after dark. A drop in light intensity to 2 fc triggers this response. Ambient temperature below 10°C curtails their movements. Weevils placed on the ground are photophobic at temperatures below 20°C and photophobic and thermophobic above 35°C. Orientation is erratic above 40°C and heat stupor occurs in a few minutes. In Michigan the pales weevil, Hylobius pales (Herbst), is sometimes a serious pest in Christmas tree plantations. It breeds in the root collar and roots of recently killed pines or freshly cut stumps. Adults feed on the bark of living pines and other conifers, degrading the shoots and making the trees less profitable at market. In a companion study (Corneil and Wilson, 1984), we investigated the dispersion and seasonal activity of the adult weevil in several Christmas tree plantations. Dispersion and seasonal activity in part were due to temperature and light intensity. This study further examines the behavior of the adults under various temperature and light conditions found in pine plantations. METHODS AND MATERIALS Field observations and tests were conducted during July and August 1979, in a Scotch pine Christmas tree plantation in Tuscola County, Michigan. Observations of adult weevils were made from 2000 to 0100 hrs EST. We recorded the time when weevils moved from the litter up onto the stem and branches to feed, as well as light intensity, temperature, and precipitation during the observation hours. A laboratory test was conducted in July 1979 to examine day and night activity. In the test, 10 male and 10 female adult weevils were placed in each of two cages (41 by 30 by 25 cm) constructed with plywood frames and ny Ion screens. The cages were positioned on a table near a window facing east, and a light meter was placed on the floor f one cage to measure light intensity. Scotch pine twigs were inserted into moist sand and placed in the center of the cage floor to provide the adults with food and a place to climb. Crumpled paper toweling was laid aroung the twigs to simulate needle litter and provide shelter. After indoor observations on three consecutive days, the cages were taken to an open field and the location and movements of adults were recorded hourly from afternoon until after dusk on four consecutive days. Locomotory and orientation behavior was observed in a grid in a clearing within the Tuscola County plantation. The 2.1 by 2.I-m grid, oriented north and south, was marked off on the ground with string at 0.3-m intervals. Small forbs and debris littered the ground, similar to conditions that normally exist between and under trees, except that there was less shade. Several Scotch pine Christmas trees were about 'Oregon Department of Forestry, Prineville, OR 97754. 2North Central Forest Experiment Station, USDA Forest Service, East Lansing, MI 48823. 1Corneil and Wilson: Some Light and Temperature Effects on the Behavior of the Adult PPublished by ValpoScholar, 1984-----~-----------------------------------------.. THE GREAT LAKES ENTOMOLOGIST Vol. 17, No, 4 226 1,5 m to the east of the grid and a mature stand of bigtooth aspen, Populus grandidentata Michx, , was about 60 m to the west. No trees were north or south of the grid for at least 200 m, Locomotory and orientation trials were made on sunny afternoons during the first two weeks of July 1979, Twelve insect trials were run when soil surface temperatures were between 12 and 25°C; 17 insect trials were run at temperatures between 3SO and 52°C, Weevils were brought to the grid in jars kept in a cooler with ice, Each jar was allowed to warm to ambient condition in the shade for at least I h before using the weevils, Ground surface temperatures and incident light intensity were monitored in the grid during each trial, using a thermister thermometer and a light meter in 1°C and I-fc intervals, respec­tively, Weevils were tracked and their trails were traced on a chart similar to the grid on the ground, They were observed up to 4 h or until they found shelter, left the grid, or died, One part of the trial w s run with a grid constructed on bare compact clay, Except for a few pebbles, the soil was free from obstructions, This situation was one a weevil would seldom encounter, but it permitted us to measure the top a weevil could travel at a set of given temperatures over unobstructed terrain, Fourteen insect trials were run on sunny afternoons at temperatures between 30° and 36°C, RESULTS During daylight, pales weevils were found on the soil beneath the litter or on the bark of the root collar of the trees, At dusk, the weevils began moving up the tree stems when the light intensity, measured at the tree surface of the foliage, dropped to 2 fc, This occurred around 2000 hrs on most clear nights and somewhat earlier on cloudy nights, On one evening that was particularly overcast, the weevils began climbing approximately 45 min earlier than on the previous evening when the sky was clear. All weevils remained near the bases of the trees when the temperature was below 10°C regardless of light intensity. Laboratory studies supported our field observations, Caged weevils remained beneath the paper toweling until light intensity inside the cages fell to 2 c; then some would climb onto the screen walls and pine twigs, During the three observation periods, about 50% of the weevils were on the cage walls or pine twigs 10-20 min after the first one arrived. When the laboratory lights were turned on, the weevils became motionless and then gradually moved to the paper toweling on the floor in 65-90 min. When cages were placed outdoors. weevils followed the same pattern, but their behav­ior was affected by temperature, One evening, when the air temperature was 5°C at dusk, all weevils remained beneath the paper toweling. During three other evenings, when temperatures were 11°C or higher at dusk, weevils began appearing when light intensity dropped to 2 fc, as they did on the trees in the field. About 50% of the weevils appeared from beneath the toweling within 25-35 min of the first weevil; males and females appeared at the same time. In the grid trials at temperatures between 12° and 25°C, the weevils moved very slowly even though in full sunlight. They did not exceed a walking speed of 8 cmlmin (Fig, I). At the start of each test, they remained motionless from 0.5 min to almost 10 min before moving about as if searching for shelter. Most stopped when they found forest debris or small plants for shelter, and most remained motionless for the rest of the test. A few, however, resumed movements later on. One insect was tracked for 115 min before it hid and ceased moving. Above 35°C the weevils moved much faster but their speed depended less on tempera­ture than terrain (Fig, I). Some weevils moved more erratically and frequently stopped beneath protective deb is, but more often moved again soon after. In the trials with temperatures above 40°C, the adults circled frequently as if desperately searching for shelter. When the weevils did not find shelter within a minute, their legs began moving erratically and they almost lost their balance. These adults entered permanent heat stupor in less than 2 min. One insect traversing the soil at 46°C soon climbed a grass blade and remained about 2 cm above the soil for almost 4 h, occasionally moving to test the soil surface, When the temperdture dropped to 34°C, the weevil left and wandered until it found a grass clump where it stayed the rest of the day. 2The Great Lakes Entomologist, Vol. 17, No. 4 [1984], Art. 8https://scholar.valpo.edu/tgle/vol17/iss4/81984 THE GREAT LAKES ENTOMOLOGIST 227 u 20 0 w a:: 40:;:) .. ~ a:: w £L ~ W I­,0 20 30 40 50 60 70 80 90 ICO CENTIMETERS PER MINUTE Fig. 1. Walking speeds of adult weevils at various soil surface temperatures in full sunlight. Several specimens at terrlpel"atulres above 40°C died in Jess than 2 min after the trials began; all others survived the test. Weevils tested on flat smooth clay at temperatures between 30° and 36°C moved from 198 to 482 cmimin with an average of 297 cmimin, more than three times faster than on normal terrain in a plantation. Most weevils remained immobile for 1-3 min at the start of each trial and then moved continuously until well outside the grid. The adults in the 35 grid trials almost always moved away from the sun (Fig. 2). Seventy-one percent of the insects oriented toward, and then moved in the direction within the quadrant directly away from the sun (i.e., 45° each side of 180° from the sun) and 91 % moved in the hemicircle opposite the sun's rays (i.e. 90° right and left of 180°). Three insects (9%) traveled toward the sun, one almost directly toward it (Fig. 2). The latter burrowed into the litter after traveling a few centimeters and remained there for most of the test. DISCUSSION In a previous study, we learned that pales weevils follow a consistent daily cycle. During the day, they remain in the litter near the base of pine trees; at night they move onto or between trees (Corneil and Wilson, 1984). This study indicates that the stimulus that initiates evening movements is a drop in light intensity to about 2 fc. Temperatures below lOoC at or after dusk curtail or halt these evening sojourns. A rise in light intensity cues the insect to return to the root collar area. It did not rain during this study, but rain probably curtails weevil movements somewhat, as it does those of the closely related pine root collar weevil, H. radicis Buchanan, (Wilson 1968). If weevils come into the open after daylight, as in the grid tests, they will respond photo-negatively and attempt to reach shelter. When soil surface temperatures are below 25°C. the weevils move slowly and react mostly to light. If they find shelter, they either st y put until conditions either improve or worsen, or they seek new hiding places. Of course, dark hiding places, like the root collar area, are seldom available in the open. Adults reaching the shade of trees usually stay put until nightfall. At 30-35°C weevils move much more rapidly, their speed depending somewhat on the roughness of the terrain and their searching behavior. They are still cued almost entirely by light, although tem­3Corneil and Wilson: Some Light and Temperature Effects on the Behavior of the Adult PPublished by ValpoScholar, 1984228 THE GREAT LAKES ENTOMOLOGIST Vol. 17, No.4 ~ ~ Fig. 2. Angles of locomotion relative to the sun and distances traveled by 35 adult pales weevils placed in a grid in full sunlight n July. Distance is shown as a straight line drawn from starting point 10 end point. Lines drawn to outer circle indicate weevil left grid. Time, not shown, ranges from less than I min to 115 min per weeviL perature may be partly involved. Their direction of travel is close to 1800 away from the sun and generally as straight as he terrain permits. In full sun at temperatures over 35°C, the weevils respond to both light and temperature cues by becoming highly photophobic and thermophobic. And above 40°C movements are aimed at survivaL The weevils must find shelter or climb above the surface or they will die within 2-3 min. Although the weevils can fly, they never do so, even under conditions that can kill them. The effects o  temperature and light on behavior and survival may explain why pales weevil adults gather beneath host pine trees as do pine root collar weevil adults (Wilson 1968). Most pales weevil adults are found at the base of host pines during the day in the summer and f IL In the spring, however, most weevils are located around stumps pro­duced from the previous harvest. This behavioral trait may be an olfactory response to the volatile resins and oils released by fresh stumps in the spring. Volatile attractants in stumps diminish by June, which coincides with an increased occurrence of adults around the living trees (Cornell and Wilson, 1984). Although the survival behavior of the pales weevil adults closely resembles that of the closely related pine root collar weevil, silvicultural treatments such as low pruning (the removal of the lower branches and the litter at the base of the trees) would probably not sufficiently deter this insect as it does the pine root collar weevil (Wilson 1967). Because the pales weevil breeds in stumps and nornlally not living pines, it still could oviposit on stumns without difficulty. Low pruning with litter scraping (pulling back the litter 0.5 m away from the tree base) would probably force the weevils away from the root collar to the piled litter where they would hide during the day. This treatment, however, would not prevent them from ascending the trees at night to feed on and injure the shoots. LITERATURE CITED Corneil, J. A. and L F. Wilson. 1984. Dispersion and seasonal activity of the pales weevil, Hylobius pales (Coleoptera:Curculionidae), in Michigan Christmas tree planta­tions. Canadian EntomoL ll6:71l-717. Wilson, L F. 1967. Effects of pruning and ground treatments on populations f the pine root collar weevil. J. Econ. EntomoL 60:823-827. 1968. Diel periodicity and survival behavior of pine root collar weevil adults under various light and temperature conditions. Ann. EntomoL Soc. Amer. 60:1490­1495. 4The Great Lakes Entomologist, Vol. 17, No. 4 [1984], Art. 8https://scholar.valpo.edu/tgle/vol17/iss4/8

Some Light and Temperature Effects on the Behavior of the Adult Pales Weevil, Hylobius Pales (Coleoptera: Curculionidae)

ValpoScholar

The Great Lakes Entomologist 
Volume 17 
Number 4 - Winter 1984 Number 4 - Winter 
1984 
Article 8 
December 1984 
Some Light and Temperature Effects on the Behavior of the Adult 
Pales Weevil, Hylobius Pales (Coleoptera: Curculionidae) 
Jeffrey A. Corneil 
Oregon Department of Forestry 
Louis F. Wilson 
USDA Forest Service 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Corneil, Jeffrey A. and Wilson, Louis F. 1984. "Some Light and Temperature Effects on the Behavior of the 
Adult Pales Weevil, Hylobius Pales (Coleoptera: Curculionidae)," The Great Lakes Entomologist, vol 17 (4) 
Available at: https://scholar.valpo.edu/tgle/vol17/iss4/8 
This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. 
It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. 
For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 
1984 THE GREAT LAKES ENTOMOLOGIST 225 
SOME LIGHT AND TEMPERATURE EFFECTS ON THE BEHAVIOR 
OF THE ADULT PALES WEEVIL, HYLOBIUS PALES 
(COLEOPTERA: CURCULIONIDAE) 
Jeffrey A. Corneil' and Louis F. Wilson2 
ABSTRACT 
Adult pales weevils react to light and temperature cues regarding their movements in 
pine plantations. They remain at the base of their host trees during the day and move onto 
the trees after dark. A drop in light intensity to 2 fc triggers this response. Ambient 
temperature below 10°C curtails their movements. Weevils placed on the ground are 
photophobic at temperatures below 20°C and photophobic and thermophobic above 35°C. 
Orientation is erratic above 40°C and heat stupor occurs in a few minutes. 
In 
Michigan the pales weevil, 
Hylobius pales (Herbst), is sometimes a serious pest in 
Christmas tree plantations. It breeds in the root collar and roots of recently killed pines or 
freshly cut stumps. Adults feed on the bark of living pines and other conifers, degrading 
the shoots and making the trees less profitable at market. 
In 
a companion study (Corneil and Wilson, 1984), 
we investigated the dispersion and 
seasonal activity of the adult weevil in several Christmas tree plantations. Dispersion and 
seasonal activity in part were due to temperature and light intensity. This study further 
examines the behavior of the adults under various temperature and light conditions found 
in 
pine plantations. 
METHODS AND MATERIALS 
Field observations and tests were conducted during July and August 1979, in a Scotch 
pine Christmas tree plantation in Tuscola County, Michigan. Observations of adult 
weevils were made from 2000 to 0100 hrs EST. 
We recorded the time when weevils 
moved from the litter up onto the stem and branches to feed, as well as light intensity, 
temperature, and precipitation during the observation hours. 
A laboratory test was conducted in July 1979 to examine day and night activity. In the 
test, 10 male and 10 female adult weevils were placed in each of two cages (41 by 30 by 
25 
cm) constructed with plywood frames and 
ny Ion screens. The cages were positioned on 
a table near a window facing east, and a light meter was placed on the floor f one cage to 
measure light intensity. Scotch pine twigs were inserted into moist sand and placed in the 
center of the cage floor to provide the adults with food and a place to climb. Crumpled 
paper toweling was laid aroung the twigs to simulate needle litter and provide shelter. 
After indoor observations on three consecutive days, the cages were taken to an open field 
and the location and movements of adults were recorded hourly from afternoon until after 
dusk on four consecutive days. Locomotory and orientation behavior was observed in a 
grid in a clearing within the Tuscola County plantation. The 2.1 by 2.I-m grid, oriented 
north and south, was marked off on the ground with string at 0.3-m intervals. Small forbs 
and debris littered the ground, similar to conditions that normally exist between and under 
trees, except that there was less shade. Several Scotch pine Christmas trees were about 
'Oregon Department of Forestry, Prineville, OR 97754. 

2North Central Forest Experiment Station, USDA Forest Service, East Lansing, MI 48823. 

1
Corneil and Wilson: Some Light and Temperature Effects on the Behavior of the Adult P
Published by ValpoScholar, 1984
-----~-----------------------------------------.. 
THE GREAT LAKES ENTOMOLOGIST Vol. 17, No, 4 226 
1,5 m to the east of the grid and a mature stand of bigtooth aspen, Populus grandidentata 
Michx, , was about 60 m to the west. No trees were north or south of the grid for at least 
200 m, 
Locomotory and orientation trials were made on sunny afternoons during the first two 
weeks of July 1979, Twelve insect trials were run when soil surface temperatures were 
between 12 and 25°C; 17 insect trials were run at temperatures between 3SO and 52°C, 
Weevils were brought to the grid in jars kept in a cooler with ice, Each jar was allowed to 
warm to ambient condition in the shade for at least I h before using the weevils, Ground 
surface temperatures and incident light intensity were monitored in the grid during each 
trial, using a thermister thermometer and a light meter in 1°C and I-fc intervals, respec­
tively, Weevils were tracked and their trails were traced on a chart similar to the grid on 
the ground, They were observed up to 4 h or until they found shelter, left the grid, or died, 
One part of the trial w s run with a grid constructed on bare compact clay, Except for a 
few 
pebbles, the soil was free from obstructions, This situation was one a weevil would 
seldom encounter, but it permitted 
us to measure the top a weevil could travel at a 
set of given temperatures over unobstructed terrain, Fourteen insect trials were run on 
sunny afternoons at temperatures between 30° and 36°C, 
RESULTS 
During daylight, pales weevils were found on the soil beneath the litter or on the bark of 
the root collar of the trees, At dusk, the weevils began moving up the tree stems when the 
light intensity, measured at the tree surface of the foliage, dropped to 2 fc, This occurred 
around 2000 hrs on most clear nights and somewhat earlier on cloudy nights, On one 
evening that was particularly overcast, the weevils began climbing approximately 45 min 
earlier than on the previous evening when the sky was clear. All weevils remained near 
the bases of the trees when the temperature was below 10°C regardless of light intensity. 
Laboratory studies supported our field observations, Caged weevils remained beneath 
the paper toweling until light intensity inside the cages fell to 2 c; then some would climb 
onto the screen walls and pine twigs, During the three observation periods, about 50% of 
the weevils were on the cage walls or pine twigs 10-20 min after the first one arrived. 
When the laboratory lights were turned on, the weevils became motionless and then 
gradually moved to the paper toweling on the floor in 65-90 min. 
When cages were placed outdoors. weevils followed the same pattern, but their behav­
ior was affected by temperature, One evening, when the air temperature was 5°C at dusk, 
all weevils remained beneath the paper toweling. During three other evenings, when 
temperatures were 11°C or higher at dusk, weevils began appearing when light intensity 
dropped to 2 fc, as they did on the trees in the field. About 50% of the weevils appeared 
from beneath the toweling within 25-35 min of the first weevil; males and females 
appeared at the same time. 
In the grid trials at temperatures between 12° and 25°C, the weevils moved very slowly 
even though in full sunlight. They did not exceed a walking speed of 8 cmlmin (Fig, I). 
At the start of each test, they remained motionless from 0.5 min to almost 10 min before 
moving about as if searching for shelter. Most stopped when they found forest debris or 
small plants for shelter, and most remained motionless for the rest of the test. A few, 
however, resumed movements later on. One insect was tracked for 115 min before it hid 
and ceased moving. 
Above 35°C the weevils moved much faster but their speed depended less on tempera­
ture than terrain (Fig, I). Some weevils moved more erratically and frequently stopped 
beneath protective deb is, but more often moved again soon after. In the trials with 
temperatures above 40°C, the adults circled frequently as if desperately searching for 
shelter. When the weevils did not find shelter within a minute, their legs began moving 
erratically and they almost lost their balance. These adults entered permanent heat stupor 
in 
less than 2 min. One insect traversing the soil at 46°C soon climbed a grass blade and 
remained about 2 cm above the soil for almost 4 h, occasionally moving to test the soil 
surface, When the temperdture dropped to 34°C, the weevil left and wandered until it 
found a grass clump where it stayed the rest 
of the day. 
2
The Great Lakes Entomologist, Vol. 17, No. 4 [1984], Art. 8
https://scholar.valpo.edu/tgle/vol17/iss4/8
1984 THE GREAT LAKES ENTOMOLOGIST 227 
u 
20 
0 
w 
a:: 40
:;:) 
.. ~ 
a:: 
w 
£L 
~ 
W 
I­
,0 
20 30 40 50 60 70 80 90 ICO 
CENTIMETERS PER MINUTE 
Fig. 1. Walking speeds of adult weevils at various soil surface temperatures in full sunlight. 
Several specimens at terrlpel"atulres above 40°C died in Jess than 2 min after the trials began; all 
others survived the test. 
Weevils tested on flat smooth clay at temperatures between 30° and 36°C moved from 
198 
to 482 cmimin with an average 
of 297 cmimin, more than three times faster than on 
normal terrain in a plantation. Most weevils remained immobile for 1-3 min at the start of 
each trial and then moved continuously until well outside the grid. 
The adults in the 35 grid trials almost always moved away from the sun (Fig. 2). 
Seventy-one percent of the insects oriented toward, and then moved in the direction within 
the quadrant directly away from the sun (i.e., 45° each side of 180° from the sun) and 91 % 
moved in the hemicircle opposite the sun's rays (i.e. 90° right and left of 180°). Three 
insects (9%) traveled toward the sun, one almost directly toward it (Fig. 2). The latter 
burrowed into the litter after traveling a few centimeters and remained there for most of 
the test. 
DISCUSSION 
In a previous study, we learned that pales weevils follow a consistent daily cycle. 
During the day, they remain in the litter near the base of pine trees; at night they move 
onto or between trees (Corneil and Wilson, 1984). This study indicates that the stimulus 
that initiates evening movements is a drop in light intensity to about 2 fc. Temperatures 
below lOoC at or after dusk curtail or halt these evening sojourns. A rise in light intensity 
cues the insect to return to the root collar area. It did not rain during this study, but rain 
probably curtails weevil movements somewhat, as it does those of the closely related pine 
root collar weevil, H. radicis Buchanan, (Wilson 1968). 
If 
weevils come into the open after daylight, as in the grid tests, they will respond 
photo-negatively and attempt to reach shelter. When soil surface temperatures are below 
25°C. the weevils move slowly and react mostly 
to light. If they find shelter, they either 
st y put until conditions either improve or worsen, or they seek new hiding places. Of 
course, dark hiding places, like the root collar area, are seldom available in the open. 
Adults reaching the shade of trees usually stay put until nightfall. At 30-35°C weevils 
move much more rapidly, their speed depending somewhat on the roughness of the terrain 
and their searching behavior. They are still cued almost entirely by light, although tem­
3
Corneil and Wilson: Some Light and Temperature Effects on the Behavior of the Adult P
Published by ValpoScholar, 1984
228 THE GREAT LAKES ENTOMOLOGIST Vol. 17, No.4 
~ ~ 
Fig. 2. Angles of locomotion relative to the sun and distances traveled by 35 adult pales weevils 
placed in a grid in full sunlight n July. Distance is shown as a straight line drawn from starting 
point 10 end point. Lines drawn to outer circle indicate weevil left grid. Time, not shown, ranges 
from less than I min to 115 min per weeviL 
perature may be partly involved. Their direction of travel is close to 1800 away from the 
sun and generally as straight as he terrain permits. In full sun at temperatures over 35°C, 
the weevils respond to both light and temperature cues by becoming highly photophobic 
and thermophobic. And above 40°C movements are aimed at survivaL The weevils must 
find shelter or climb above the surface or they will die within 2-3 min. Although the 
weevils can fly, they never do so, even under conditions that can kill them. 
The effects o  temperature and light on behavior and survival may explain why pales 
weevil adults gather beneath host pine trees as do pine root collar weevil adults (Wilson 
1968). Most pales weevil adults are found at the base of host pines during the day in the 
summer and f IL In the spring, however, most weevils are located around stumps pro­
duced from the previous harvest. This behavioral trait may be an olfactory response to the 
volatile resins and oils released by fresh stumps in the spring. Volatile attractants in 
stumps diminish by June, which coincides with an increased occurrence of adults around 
the living trees (Cornell and Wilson, 1984). 
Although the survival behavior of the pales weevil adults closely resembles that of the 
closely related pine root collar weevil, silvicultural treatments such as low pruning (the 
removal of the lower branches and the litter at the base of the trees) would probably not 
sufficiently deter this insect as it does the pine root collar weevil (Wilson 1967). Because 
the pales weevil breeds in stumps and nornlally not living pines, it still could oviposit on 
stumns without difficulty. Low pruning with litter scraping (pulling back the litter 0.5 m 
away from the tree base) would probably force the weevils away from the root collar to the 
piled litter where they would hide during the day. This treatment, however, would not 
prevent them from ascending the trees at night to feed on and injure the shoots. 
LITERATURE CITED 
Corneil, J. A. and L F. Wilson. 1984. Dispersion and seasonal activity of the pales 
weevil, Hylobius pales (Coleoptera:Curculionidae), in Michigan Christmas tree planta­
tions. Canadian EntomoL ll6:71l-717. 
Wilson, L F. 1967. Effects of pruning and ground treatments on populations f the pine 
root collar weevil. J. Econ. EntomoL 60:823-827. 
1968. Diel periodicity and survival behavior of pine root collar weevil adults 
under various light and temperature conditions. Ann. EntomoL Soc. Amer. 60:1490­
1495. 
4
The Great Lakes Entomologist, Vol. 17, No. 4 [1984], Art. 8
https://scholar.valpo.edu/tgle/vol17/iss4/8


https://scholar.valpo.edu/cgi/viewcontent.cgi?article=1525&amp;context=tgle

Some Light and Temperature Effects on the Behavior of the Adult Pales Weevil, Hylobius Pales (Coleoptera: Curculionidae)

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