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PSYCHE

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Mary L. Corn.
Notes on the Biology of Polistes carnifex (Hymenoptera, Vespidae) in Costa Rica and Colombia.
Psyche 79:150-157, 1972.

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NOTES ON THE BIOLOGY OF
POLISTES CARNIFEX (HYMENOPTERA, VESPIDAE) IN COSTA RICA AND COLOMBIA*
BY MARY L. CORN
The Biological Laboratories, Harvard University Cambridge, Massachusetts 02 I 38
According to Bequaert ( 1936), Polistes carnifex (Fabricius) is the largest representative of the genus in the Neotropics. Its distribu- tion extends from northern Argentina to Mexico. Little is known of its biology or behavior. Bertoni (191 I) described a nest from Paraguay; Bequaert ( 1936) named new color varieties; Reid ( 1942) studied the developmental stages; and Weyrauch (1942) described a nest of P. carnifex var. boliviensis in Peru. These authors noted that carnifex builds a pendant, horizontal, open-faced nest with a single, central pedicel. The pedicel is covered with a tough, dark, gelatin-like material.
Mv observations were conducted in 2 areas. Site A was near Palo Verde, Guanacaste Province, Costa Rica. Six nests were taken there in July, 1971, in the rainy season. Site B was in the vicinity of Cali, Colombia, where I observed an individual nest for over 30 hours over a 2 week period at the close of the dry season in Jan- uary, 1972.
At Site A the six nests were among dozens of carnifex nests in various low, shrubby, thorn bearing trees, some of which were legumes, though several species were represented. The trees grew along the edge of a large seasonal swamp. Most of the nests were associated with (that is, in the same tree, less than I m from) large nests of a polybiine, probably Polybia sp. Rarely, a third wasp, Mis- chocyttarus sp. nested in the same cluster. Windsor (1972) has found an association of Polybia and Mischocyttarus in the same province, but carnifex was rarely found in it, though the other two species are possibly the same. At site A, the nests of all 3 species sometimes occurred within I m of each other. Since many trees con- tained no nests of carnifex at all, the distribution seemed non-ran- dom. The association of carnifex with other species of social wasps has not been reported elsewhere.
P. carnifex was much less aggressive than its size might suggest. Entire nests were captured safely at night. Only two a,dults were *Manuscript received by the editor May 8, 1972. 150




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Corn - Poliste,r carmfex
Table 1
Adult populations of six nests of Polistes carnifex. Number of Females
in Each Reproductive
Associated Total Adult Class (see Text)* Nest with Polybia Population
Male A B C
2 +
13 1
0 1 9
3A + 13
0 4 1 6
4 4- 8**
2 0 1 3
B6a 8
0 0 1 5
B6b
4
.. 0 0 0 2
B7
8
0 1 0 5
* The sum of males and females listed here does not equal the total popu- lation because two specimens were saved for identification from each nest. **Two specimens escaped from this nest; therefore, only six animals were examined.
known to have escaped and both of these were from nest number 4. Three of the nests were associated with polybiine nests; 3 were not. The maximum nest size was about 9 cm in diameter. In one nest, cells from which at least one emergence had occurred had an aver- age length of 27.8 mm (s = 2.770 mm). In all of the nests, the central cells were in at least their second cycle of brood, that is, the age of the nests was greater than I according to the terminology of Richards and Richards ( I 95 I ) .
The total adult population on these nests ranged from 4 to 13 (Table I). All but 2 of the adults from each nest were dissected. The remainder were saved for identification and have been deposited in the Harvard Museum of Comparative Zoology and the British Museum of Natural History. The dissected females were divided into the following 3 categories: (A) those females with 4 or more full-sized eggs; (B) those females with 1-3 full-sized eggs; and (C)
those females with no full-sized eggs. The last category in- cluded 5 females with very small eggs.
Table I shows that not all
nests included a female with well developed ovaries. Possibly laying females were among those saved for identification. Table 2 shows the number of eggs, larvae, capped cells (pre- pupae and pupae), and empty cells in each nest. There was no
clear evidence of parasitism in any of the nests. In 3 cells, there
was an additional egg, but these eggs seemed to be carnifex eggs, rather than parasites. Ten arbitrarily selected larvae were dissected. They showed no evidence of parasitism.
Unfortunately, time was too short for behavioral studies at this site. However, it is clear that there are no obvious differences be-



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Table 2
Class distribution of immature forms in six nests of Polistes carnifex. Associated Empty Capped Total Average number of Nest withPolyb'ia Cells Eggs Larvae Cells Immatures immatures/adult Q 2 + 6 5 1
25 19 9 5 7.92 2
3A +
10 22 41 17 80 6.15 Q
'^*
3 + 3 37 2 8 11 7 6 *
a-
'a
B6a 3 3 5 22 2 3 8 0 10.00
B6b - 5 12 2 0 6 3 8 9.51
B 7
-
3 26 3 3 19 7 8 9.76
*This value is between 19.0 and 12.6, depending on whether 0, 1, or 2 of the escaped animals were females.



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19721 Corn - Poliste~ carnifex 153
tween associated and nonassociated nests in the incidence of para- sitism, the size of the adult population, or the average number of immatures per adult female.
The nest at site B was under the eaves of a tin roof of an aban- doned 'house.
There were no other wasps' nests nearby. The nest structure was similar to that of the Costa Rican nests, except that the closed cells had flat recessed caps rather than convex caps as in Costa Rica. These cells average about 30.0 mm in overall length (s = 2.030 mm), a mean which was significantly larger than the mean of the Costa Rican nests (Fisher-Behrens test, d = 2.8851, @ = 73'9 Vi, V2 = 35, 10, p < 0.05).
Most of the observations on this nest were made during hours of bright sunshine, when the wasps forage. The 2 adults present on the nest initially were marked at the beginning of the study. Others were marked within a day or 2 after emergence. (See Table 3.) The number of cells (28) remained constant throughout the 17 days of observation.
Only one cell, a peripheral one, was observed being enlarged. The queen brought in a ball of freshly macerated pulp and applied it herself, after unsuccessful attempts to divide it among her nestmates.
Her behavior in applying the pulp was the same as that described by Eberhard (1969) in P. fuscatus. The queen applied the load with her mandibles, while holding her fore- tarsi on either side of the wall under construction. As she worked
she moved her antennae in circles beside her head, touching the
opposite, parallel wall as she did so.
According to Eberhard, it is
the antenna1 contact with the opposite cell walls which enables the Table 3
Seventeen day history of a five membered colony of Polistes carnifex near Cali, Colombia. The solid line indicates presence on the nest. The dashed line indicates periods of foraging. Female No. 1 had developed ovaries.
Female
No.
1
-----------------
5 *______
Jan. Feb.
16 18 20 22 24 26 28 30 1
^emerged
fdied or disappeared




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1 54 Psyche [September
wasp to form straight sides on the inner walls of the cell. Con- versely, it is the lack of antenna1 contact along the outer margin of a peripheral cell which causes those walls to be rounded. Dominance interactions between females were never very ag- gressive. The highest ranking wasp on the nest invariably received food first from the returning forager. The higher ranking wasp generally held its body farther from the substrate than the sub- ordinate during the feeding (see Fig.
I). The solicitor tilted its
head to one side during the exchange and antennated the face of the donor. Occasionally, the solicitor, and especially the queen, held onto the donor and prevented her escape. Dominance interactions unrelated to food exchange were rare. In one of the few observed, the queen, apparently unprovoked, moved toward the third ranking individual and, holding her with her prothoracic legs, began to bite the subordinate about the man- dibles, eyes, neck, thorax and wings. The subordinate held her body very close to the nest. When she tried to back away, the queen held her and began biting more vigorously. When the attack ceased, the subordinate retreated to a position on top of the nest, while the queen returned to the face of the nest.
When I disturbed the nest severely, the wasps showed typical threat behavior. At low intensities, the wasp faced the disturbance and raised and spread its wings. At higher intensities, the aroused individual buzzed its wings in short bursts. It was this action which seemed to arouse the nestmates. If the disturbance was very in- tense (as when I was marking the wasps) the females would fly off the nest and circle it a few feet away. After such intense dis- turbances, buzzing threat displays continued for up to 10 minutes. Foragers about to leave the nest held themselves erect on the nest, buzzed their wings loudly, paused for a moment, and then took off. A brief orientation flight generally followed. The re- turning foragers sometimes made a number of approaches before alighting on the nest. Occasionally the wasp landed on a rafter adjacent to the nest, groomed for a moment, and then took off and landed on the nest immediately. The queen herself made 5 of the 29 foraging trips seen in this study. On the 29 trips, the foragers brought 25 loads of nectar, 3 loads of macerated greenish-gray prey, and I load of pulp.
The returning forager fed the highest ranking resident first and then she and the solicitor fed the larvae (see Fig. 2). The wasps stuck their heads into the cells and then rapidly antennated the op- posite wall of the cell. The sound produced by the antennae striking



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19721 Corn - Polisfef camifex 155




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156 Psyche
[September
the cell was easily audible at a distance of I m from the nest. Pos- sibly this behavior alerted the larvae to the food offering. After feeding 2 or 3 larvae, the forager usually groomed briefly and then took off. The entire exchange sometimes took as little as 2 minutes. When a third wasp was present on the nest, it sometimes tried to steal food during the exchange. In one case, when the third wasp managed to obtain a large amount of nectar, the exchange ended with the donor biting the intruder.
As the queen moved about the nest, she often dragged her ab- domen across the face of the nest, and moved it slightly from side to side in the process. Other wasps showed the same behavior but less consistently. The queen and the second ranking female both showed a peculiar behavior of rubbing their abdomens over the pedicel of the nest; the queen twice and the second ranking female 4 times. A similar behavior was reported by Jeanne ( 1970) in Mischocyttarus drewseni. He showed that wasps in that species were depositing a substance which is repellent to ants. On only one occasion was the queen observed eating an egg. The process took about 3 minutes. She did not lay another egg in the cell. In fact, I did not see any of the wasps ovipositing during all of my observations, though nest records show that they must have laid at least 4 eggs during the 17 days. At the end of the observa- tion period, the queen was dissected and found to contain 4 ripe eggs and a full spermatheca.
The behavioral repertoire of this wasp is very similar to that of P. canadensis as reported by Eberhard (1969). The size and gen- tleness of this wasp make it very suitable for behavioral observa- tions. The association of P. carnifex with other social wasps has not been reported outside of 'Costa Rica. Data on the nesting suc- cess in associated and non-associated nests are needed to determine what a.dvantage, if any, Polistes carnifex receives or confers in this association.
Part of this study was a field project in the Tropical Ecology course ( 1971) of the Organization for Tropical Studies. I am grateful to Peter Becker, Valerie Dryer, Doug Gill, Julie Multcr, and A1 Muth, who made heroic efforts collecting the nests in Costa



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19721 Corn - Poliste~ earnifex 157
Rica.
I am also very grateful to Drs. William and Mary Jane Eberhard for their hospitality during my stay in Colombia and for their valuable discussion and assistance in these observations. M. J. W. Eberhard dissected the queen from Colombia. Prof. 0. W. Richards kindly identified the specimens of Polistes. This research has received partial support from NSF Grant No. GB27911; R. C. Rollins, Harvard University, principal investigator. Roger Swain, Robert Silberglied and Dr. H. E. Evans provided helpful comments on the manuscript. This paper is published with the aid of a grant from the Museum of Comparative Zoology at Harvard University. BEQUAERT, J.
1936. Color variation in the South American social wasp, Polistes carnifex (Fabricius) (Hymenoptera, Vespidae) . Rev. Entomol. (Rio de Janeiro), 6: 376-383.
BERTONI, A.
1911. Contribution a la biologia de las avispas y abejas del Paraguay. Anal. Mus. Nac. Bs. As. Ser. 3. 15: 97-146. EBERHARD, M. J. W.
1969. The social biology of polistine wasps. Misc. Publ. Mus. 2001. U. Mich. No. 140. 101 pp.
JEANNE, R. L.
1970.
Chemical defense of brood by a social wasp. Science, 168: 1465- 1466.
REID, J. A.
1942. On the classification of the larvae of the Vespidae (Hymenoptera). Trans. Roy. Entomol. Soc. Lond., 92: 285-331. RICHARDS, O.W. and M. J. RICHARDS
1951. Observations on the social wasps of South America (Hymenoptera, Vespidae). Trans. Roy. Entomol. Soc. Lond., 102 : 1-170. WEYRAUCH, W.
1942. Nidos de insectos peruanos en el Museo de Historia Natural. Bol. Mus. Hist. Nat. (Lima), 6: 52-66.
WINDSOR, D.
1972. Nesting association between two Neotropical polybiine wasps. Biotropica (in press).




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