(excerpt)
Southwood (1973) concluded that pollen feeding was probably the first step in the development of the phytophagous habit in insects, because pollen, compared with plant foliage, is rich in nutrients and low in sewndary defense substances. Surprisingly, little is known about insects that feed mainly on pollen. For example, in a bibliography of insects that feed on reproductive structures of North American conifers (Barcia and Merkel, 1972), less than three per cent of 719 references pertained to pollen feeders. This note reports on the kinds and abundance of insects found inhabiting clusters of fresh staminate or male strobili (MS) of 60- to 65-year-old red pine trees in two seed production areas (SPAs) in northern Minnesota

Mattson, William J

English

ValpoScholar

The Great Lakes Entomologist 
Volume 8 
Number 4 - Winter 1975 Number 4 - Winter 
1975 
Article 9 
December 1975 
Abundance of Insects Inhabiting the Male Strobili of Red Pine 
William J. Mattson 
USDA Forest Service 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Mattson, William J. 1975. "Abundance of Insects Inhabiting the Male Strobili of Red Pine," The Great Lakes 
Entomologist, vol 8 (4) 
Available at: https://scholar.valpo.edu/tgle/vol8/iss4/9 
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. 
THE GREAT LAKES ENTOMOLOGIST 
ABUNDANCE OF INSECTS INHABITING 
THE MALE STROBlLl OF RED PINE 
William J. Mattsonl 
Southwood (1973) concluded that pollen feeding was probably the first step in 
the development of the phytophagous habit in insects, because pollen, compared with plant 
foliage, is rich in nutrients and low in sewndary defense substances. Surprisingly, little is 
known about insects that feed mainly on pollen. For example, in a bibliography of 
insects that feed on reproductive structures of North American conifers (Barcia and 
Merkel, 1972), less than three per cent of 719 references pertained to pollen feeders. This 
note reports on the kinds and abundance of insects found inhabiting clusters of fresh 
staminate or male strobili (MS) of 60- to 65-year-old red pine trees in two seed 
production areas (SPAs) in northern Minnesota. 
METHODS 
Just before pollen dispersal in the first week of June 1969, at the Birch Hill and 
Portage Lake SPAs, I selected ten trees at random and stratified the crown of each tree 
into six cells (upper, middle, and lower levels, of both north and south sides). I counted 
all branches in each cell and picked one at random. Then I randomly selected the right or 
left side of each sample branch and collected all MS from the side for later counting and 
dissection in the laboratory to recover the insects in the MS. To estimate the total 
numbers of insectsltree, I added the branch counts and multiplied by the number of 
branches in that level, and then summed all levels. To determine if there were significant 
differences in insect and flower density associated with the various strata, I subjected the 
data to  analyses of variance. Finally, I regressed insect densities against flower densities 
per branch and per tree to determine if there were significant relations between these 
variables. 
RESULTS AND DISCUSSION 
Xyelid sawflies (Xyek sp., probably minor), considered to be among the most 
primitive Hymenoptera, were clearly the most abundant insects in MS. Other common 
species were the jack pine budworm (Choristoneura pinus Freeman: Tortricidae), the 
flower moth (Eucordylea sp.: Gelechiidae), the cone worm (Dioryctrkz disclusl Heinrich: 
Pyralidae), the Zimmerman pine moth (D. zimmermani (Grate)), and occasional immature 
lacewings (Neuroptera: Hemerobiidae), plant bugs (Hemiptera: Miridae), and thrips 
(Thysanoptera: Thripidae). Color photos of and biological notes on most of these insects 
can be found in Rose and Lindquist (1973). The relative abundance of each species in 
both study areas is shown in the following tabulation: 
(in per cent) 
Eucordylea sp., 
Xyek sp. C. pinus Dioryctria spp. and other species 
Birch Hill SPA 96.3 1.2 1.5 1.0 
Portage Lake SPA 51.5 27.2 3.6 17.7 
Mean counts k one standard error per tree and per acre, respectively, for all species 
combined were 10.6 k 2.1 and 672 2 130 thousand at  Birch Hill, and 3.7 k 1.1 and 
419 2 126 thousand at Portage Lake. 
llnsect Ecologist, North Central Forest Experiment Station, USDA Forest Service, St. 
Paul, Minnesota 5 51 08. 
1
Mattson: Abundance of Insects Inhabiting the Male Strobili of Red Pine
Published by ValpoScholar, 1975
238 THE GREAT LAKES ENTOMOLOGIST Vol. 8, No. 4 
Insect densitieslbranch were least in the upper and greatest in the middle-crown 
(Table 1). Differences in insect density were significant (p _< .05) between upper and 
middle-crowns but not between other levels, nor between north and south sides. MS 
densities were also least in the upper crown but were not different between lower and 
middle-cro wns. 
Densities of Xyela sp. increased as a power function of MSIbranch in all levels except 
one (upper crown at Portage Lake) (Table 2). Densities of other species increased as a 
linear function of MSIbranch in all but two levels. Covariance analyses revealed that the 
regressions for Xyela were significantly different among crown levels at Birch Hill but not 
at  Portage Lake. The regressions for other species were different among all crown levels 
at  both areas. This implies, therefore, that the differences in insect density among levels 
were due in most cases to other factors besides variations in MSIbranch. 
Differences in the mathematical relations between densities of Xyela and other species 
and MSIbranch probably stem from the fact that X y e h  sp. deposit their eggs directly in 
MS or expanding buds, whereas other species deposit their eggs on foliage or branches 
and the resulting larvae must search for MS. Little is known about the behavior of adult 
Xyelids except for Ebel's (1966) report that they often form large warms around 
flowering pines to mate and feed. 
Table 1. Mean insect densities per one-half branch in different crown levels at two seed 
production areas. Means followed by the sameletters a?e not significantly @ 1 . 0 5 )  different. 
BIRCH HILL 
Overall 
Insect species Upper Middle Lower mean 
Xyela sp. 52.la 116.5b 73.lab 80.5 
Other spp. 2.2a 4.9b 3.0ab 3.4 
Ratio: 
Insects/male strobilus cluster 8.7a 5.5ab 3.3b 4.9 
PORTAGE LAKE 
Xyela sp. 10.5a 30.la 36.4a 25.7 
Other spp. 4.4a 11.5b 10.3ab 8.7 
Ratio: 
Insects/male strobilus cluster 2.la 2.0a 2.2a 2.1 
Table 2. Mathematical relations between the numbers of insects ( Y )  and male strobili (XIS) 
per branch in different crown levels at two seed production areas. 
BIRCH HILL 
Crown 
level Xyela sp. log(Y) = r2 Other species Y = ? n 
Upper .51 + 1.31 1ogMS .71 1.39 + .19MS n.s.* 14 
Middle .73 + .98 1ogMS .74 .05 + .22MS .40 19 
Lower .53 + .93 1ogMS .65 -.50 + .15MS .49 20 
PORTAGE LAKE 
-- 
Uvver .61 + 7 5 2  loeMS n.s.* -.51 + .75MS .74 9 
~ i i d l e  - .55 + 1.73 1 0 ; ~ s  .74 3.58 + .25MS n.s.* 10 
Lower - .67 + 1.69 logMS .77 -.67 + .50MS .93 10 
2
The Great Lakes Entomologist, Vol. 8, No. 4 [1975], Art. 9
https://scholar.valpo.edu/tgle/vol8/iss4/9
1975 THE GREAT LAKES ENTOMOLOGIST 239 
The abundance of aU species was highly correlated (I = .93, p = .01) with MS/tree at 
Birch Hill but only weakly correlated (I = 5 5 ,  p = . lo) at  Portage Lake. Densities of 
MS/tree were roughly equal at  both areas but Birch Hill had nearly three times as many 
insects/tree. Birch Hill may have had more insects in 1969 because of greater MS 
abundance in the preceding years. One would suspect this to  be true because the Birch 
HiU stand was only half as dense (63 stems/acre) as the Portage Lake stand and 
productivity of male and female strobililtree is known to  increase with decreased tree 
density. 
LITERATURE CITED 
Barcia, D. R., and E. P. Merkel. 1972. Bibliography on insects destructive to flowers, 
cones, and seeds of North America conifers. USDA For. Serv. Res. Pap. SE-92, 80 p. 
Southeast. For. Exp. Sta. 
Ebel, B. H. 1966. Rearing and occurrence of Xyelid sawflies on slash and long-leaf pines in 
north Florida (Hymenoptera: Xyelidae). Ann. Entomol. Soc. Amer. 59(1):227-229. 
Rose, A. H., and 0. H. Lindquist. 1973. Insects of eastern pines. Can. For. Serv. Pub. 
1313, 127 p. Ottawa, Ontaiio. 
Southwood, T. R. E. 1973. The insect/plant relationship-an evolutionary perspective. 
p. 3-30. I n  Insect/plant relationships. Royal Entomol. Soc. London Symp. 6. 215 p. 
H. F. van Emden, ed. Oxford, England. 
3
Mattson: Abundance of Insects Inhabiting the Male Strobili of Red Pine
Published by ValpoScholar, 1975


Abundance of Insects Inhabiting the Male Strobili of Red Pine

Valparaiso University

The Great Lakes Entomologist Volume 8 Number 4 - Winter 1975 Number 4 - Winter 1975 Article 9 December 1975 Abundance of Insects Inhabiting the Male Strobili of Red Pine William J. Mattson USDA Forest Service Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Mattson, William J. 1975. "Abundance of Insects Inhabiting the Male Strobili of Red Pine," The Great Lakes Entomologist, vol 8 (4) Available at: https://scholar.valpo.edu/tgle/vol8/iss4/9 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. THE GREAT LAKES ENTOMOLOGIST ABUNDANCE OF INSECTS INHABITING THE MALE STROBlLl OF RED PINE William J. Mattsonl Southwood (1973) concluded that pollen feeding was probably the first step in the development of the phytophagous habit in insects, because pollen, compared with plant foliage, is rich in nutrients and low in sewndary defense substances. Surprisingly, little is known about insects that feed mainly on pollen. For example, in a bibliography of insects that feed on reproductive structures of North American conifers (Barcia and Merkel, 1972), less than three per cent of 719 references pertained to pollen feeders. This note reports on the kinds and abundance of insects found inhabiting clusters of fresh staminate or male strobili (MS) of 60- to 65-year-old red pine trees in two seed production areas (SPAs) in northern Minnesota. METHODS Just before pollen dispersal in the first week of June 1969, at the Birch Hill and Portage Lake SPAs, I selected ten trees at random and stratified the crown of each tree into six cells (upper, middle, and lower levels, of both north and south sides). I counted all branches in each cell and picked one at random. Then I randomly selected the right or left side of each sample branch and collected all MS from the side for later counting and dissection in the laboratory to recover the insects in the MS. To estimate the total numbers of insectsltree, I added the branch counts and multiplied by the number of branches in that level, and then summed all levels. To determine if there were significant differences in insect and flower density associated with the various strata, I subjected the data to  analyses of variance. Finally, I regressed insect densities against flower densities per branch and per tree to determine if there were significant relations between these variables. RESULTS AND DISCUSSION Xyelid sawflies (Xyek sp., probably minor), considered to be among the most primitive Hymenoptera, were clearly the most abundant insects in MS. Other common species were the jack pine budworm (Choristoneura pinus Freeman: Tortricidae), the flower moth (Eucordylea sp.: Gelechiidae), the cone worm (Dioryctrkz disclusl Heinrich: Pyralidae), the Zimmerman pine moth (D. zimmermani (Grate)), and occasional immature lacewings (Neuroptera: Hemerobiidae), plant bugs (Hemiptera: Miridae), and thrips (Thysanoptera: Thripidae). Color photos of and biological notes on most of these insects can be found in Rose and Lindquist (1973). The relative abundance of each species in both study areas is shown in the following tabulation: (in per cent) Eucordylea sp., Xyek sp. C. pinus Dioryctria spp. and other species Birch Hill SPA 96.3 1.2 1.5 1.0 Portage Lake SPA 51.5 27.2 3.6 17.7 Mean counts k one standard error per tree and per acre, respectively, for all species combined were 10.6 k 2.1 and 672 2 130 thousand at  Birch Hill, and 3.7 k 1.1 and 419 2 126 thousand at Portage Lake. llnsect Ecologist, North Central Forest Experiment Station, USDA Forest Service, St. Paul, Minnesota 5 51 08. 1Mattson: Abundance of Insects Inhabiting the Male Strobili of Red PinePublished by ValpoScholar, 1975238 THE GREAT LAKES ENTOMOLOGIST Vol. 8, No. 4 Insect densitieslbranch were least in the upper and greatest in the middle-crown (Table 1). Differences in insect density were significant (p _< .05) between upper and middle-crowns but not between other levels, nor between north and south sides. MS densities were also least in the upper crown but were not different between lower and middle-cro wns. Densities of Xyela sp. increased as a power function of MSIbranch in all levels except one (upper crown at Portage Lake) (Table 2). Densities of other species increased as a linear function of MSIbranch in all but two levels. Covariance analyses revealed that the regressions for Xyela were significantly different among crown levels at Birch Hill but not at  Portage Lake. The regressions for other species were different among all crown levels at  both areas. This implies, therefore, that the differences in insect density among levels were due in most cases to other factors besides variations in MSIbranch. Differences in the mathematical relations between densities of Xyela and other species and MSIbranch probably stem from the fact that X y e h  sp. deposit their eggs directly in MS or expanding buds, whereas other species deposit their eggs on foliage or branches and the resulting larvae must search for MS. Little is known about the behavior of adult Xyelids except for Ebel's (1966) report that they often form large warms around flowering pines to mate and feed. Table 1. Mean insect densities per one-half branch in different crown levels at two seed production areas. Means followed by the sameletters a?e not significantly @ 1 . 0 5 )  different. BIRCH HILL Overall Insect species Upper Middle Lower mean Xyela sp. 52.la 116.5b 73.lab 80.5 Other spp. 2.2a 4.9b 3.0ab 3.4 Ratio: Insects/male strobilus cluster 8.7a 5.5ab 3.3b 4.9 PORTAGE LAKE Xyela sp. 10.5a 30.la 36.4a 25.7 Other spp. 4.4a 11.5b 10.3ab 8.7 Ratio: Insects/male strobilus cluster 2.la 2.0a 2.2a 2.1 Table 2. Mathematical relations between the numbers of insects ( Y )  and male strobili (XIS) per branch in different crown levels at two seed production areas. BIRCH HILL Crown level Xyela sp. log(Y) = r2 Other species Y = ? n Upper .51 + 1.31 1ogMS .71 1.39 + .19MS n.s.* 14 Middle .73 + .98 1ogMS .74 .05 + .22MS .40 19 Lower .53 + .93 1ogMS .65 -.50 + .15MS .49 20 PORTAGE LAKE -- Uvver .61 + 7 5 2  loeMS n.s.* -.51 + .75MS .74 9 ~ i i d l e  - .55 + 1.73 1 0 ; ~ s  .74 3.58 + .25MS n.s.* 10 Lower - .67 + 1.69 logMS .77 -.67 + .50MS .93 10 2The Great Lakes Entomologist, Vol. 8, No. 4 [1975], Art. 9https://scholar.valpo.edu/tgle/vol8/iss4/91975 THE GREAT LAKES ENTOMOLOGIST 239 The abundance of aU species was highly correlated (I = .93, p = .01) with MS/tree at Birch Hill but only weakly correlated (I = 5 5 ,  p = . lo) at  Portage Lake. Densities of MS/tree were roughly equal at  both areas but Birch Hill had nearly three times as many insects/tree. Birch Hill may have had more insects in 1969 because of greater MS abundance in the preceding years. One would suspect this to  be true because the Birch HiU stand was only half as dense (63 stems/acre) as the Portage Lake stand and productivity of male and female strobililtree is known to  increase with decreased tree density. LITERATURE CITED Barcia, D. R., and E. P. Merkel. 1972. Bibliography on insects destructive to flowers, cones, and seeds of North America conifers. USDA For. Serv. Res. Pap. SE-92, 80 p. Southeast. For. Exp. Sta. Ebel, B. H. 1966. Rearing and occurrence of Xyelid sawflies on slash and long-leaf pines in north Florida (Hymenoptera: Xyelidae). Ann. Entomol. Soc. Amer. 59(1):227-229. Rose, A. H., and 0. H. Lindquist. 1973. Insects of eastern pines. Can. For. Serv. Pub. 1313, 127 p. Ottawa, Ontaiio. Southwood, T. R. E. 1973. The insect/plant relationship-an evolutionary perspective. p. 3-30. I n  Insect/plant relationships. Royal Entomol. Soc. London Symp. 6. 215 p. H. F. van Emden, ed. Oxford, England. 3Mattson: Abundance of Insects Inhabiting the Male Strobili of Red PinePublished by ValpoScholar, 1975

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Abundance of Insects Inhabiting the Male Strobili of Red Pine

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