B. W. Betz.
The biology of Trichadenotecnum alexanderae Sommerman (Psocoptera: Psocidae). III. Analysis of mating behavior.
Psyche 90:97-118, 1983.

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THE BIOLOGY OF TRICHADENOTECNUM ALEXANDERAE SOMMERMAN (PSOCOPTERA: PSOCIDAE).
111. ANALYSIS OF MATING BEHAVIOR
Several authors have described mating behavior in species of Pso- coptera (Pearman 1928, Sommerman 1943a, 1943b, 1944, 1956, Badonnel 195 1, Thornton and Broadhead 1954, Klier 1956, Mock- ford 1957, 1977, Broadhead 1961, Eertmoed 1966). Only one or at most a few matings in a species were observed. This paper presents a comprehensive analysis of pre- through post-copulatory behavior in Trichadenotecnum alexanderae Sommerman. Evidence is presented for a sex-attractant pheromone, produced only by females that were receptive to mating.
Trichadenotecnum alexanderae is a relatively common psocid in eastern United States (Betz 1983a). The species inhabits trees and rock outcroppings providing its principal food source, pleurococ- cine algae. Betz (1983a) found that T. alexanderae is capable of facultative thelytoky. Formerly, the species was confused morpho- logically with three other species, all obligatorily thelytokous, which have been identified and described as T. castum Betz, T. merum Betz, and T. innupturn Betz (Betz 1983a). This paper is part of a series (cf. Betz 19830, c, d) detailing the life history of T. alexanderae,
MATERIALS AND METHODS
Cultures of T. alexanderae were obtained from three populations in Illinois: at Moraine View State Park (McLean County), along the Sangamon River at Lake of the Woods (Champaign County), and along the Salt Fork River at Champaign County Forest Preserve District-Homer Lake (Champaign County).
Specimens were collected from tree trunks with an aspirator and kept with pieces of bark in cotton-stoppered test tubes. Cultures were transported to the laboratory over ice-water in a cooler. 11000 North Lake Shore Drive, Chicago, Illinois, 6061 1 Manuscript received by the editor August 16, 1982.



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98 Psyche [VOL 90
Laboratory cultures were kept in cotton-stoppered test tubes. Each tube was supplied ad libitum with food in the form of pleuro- coccine algae on bark. Culture tubes were stored in closed, glass desiccator jars over a saturated potassium chloride (KC1) solution to maintain a relative humidity of 80 3%. The temperature regimen for rearing was 23.3' : 18.0å¡ light:dark, and the photoperiod was 15 h light9 h dark. Illumination was 4300 lumens/m*, supplied by incandescent and fluorescent lamps.
Because the other species of the T. alexanderae complex are oblig- atorily thelytokous and often occur sympatrically with the biparental species, I began a laboratory culture of T. alexanderae from each locality with females mated in the laboratory to assure the identity of the culture as the biparental species. Several breeding pairs were used to begin a culture, an attempt to represent the genetic diversity of the original sample from the field population. I also examined the morphology of the original breeding pairs to verify that they were T. alexanderae. I used bark obtained only from the original field locality in cultures; bark was examined for eggs before it was placed in a culture.
Mating behavior was studied in adults from Lake Dawson, Lake of the Woods, and Salt Fork cultures. Adults were isolated as late stage nymphs and reared in shell vials (four dram size). Each vial was supplied with a flat piece of bark which lessened the interference of the substrate on mating behavior. Females were 2-3 days old and males were 2-5 days old when brought together, the times when they were the most receptive to mating (Betz 1983~). Isolated specimens were brought together by the following method. The cotton stopper on each vial was removed, the open ends of pairs of vials were apposed, and the vials were tilted carefully until the piece of bark in the vial containing a male contacted the bark in the vial containing a female. The open ends of pairs of vials were kept together and the vials were not moved during observation of the insects. The method I used to bring together isolated specimens did not appear to disturb the insects greatly, and thus probably provided accurate observa- tions of courtship behavior.
Precopulatory Behavior
The behavior of male and female T. alexanderae was-somewhat variable among the successful matings (N = 99) and the unsuccessful



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19831 Bet: - Biology of Trichadenotecnum 99 attempts (N = 45) 1 observed. Most precopulatory behavior fol- lowed the patterns outlined in Figure 1. When bark bearing an isolated, receptive female was brought together with bark bearing a sexually active male, the male always ran onto the female's bark. A male displayed a higher level of activ- ity under these conditions than if his piece of bark was brought together with bark bearing a nymph, a female of T. alexanderae in an unreceptive state, or a piece of bark without an insect (N = 7). In five of the mating encounters I observed, the male flew onto the female's bark before the two pieces of bark were touching. This higher level of activity in males occurred even if females were placed out of the males' sight. Almost immediately after a male ran onto the bark of a female, he began a search over the substrate. Sometimes a female remained motionless during this search, even though she might have been active prior to the introduction of a male. The manner in which males elicited this reaction of females remains unknown, although the reaction may have resulted from the slight disturbance caused by the introduction of pieces of bark into the females' vials.
A male searched in the direction of a female, often stopping momentarily to flick his antennae and adjust his course. When a male approached within about 1 cm of a receptive female he began a quick, sideways gait while moving toward her, even though she may have remained hidden from the male's view. The sideways gait lasted about 1-2 seconds. Occasionally a male ap- proached a receptive female, or courted her, without the sideways gait (N = 12). Females always fled from these encounters. When a female fled, a male remained in the vicinity of the encounter and spun completely around one or more times flicking his antennae. Then a male usually ran off in the general direction of a female's flight. Unless unsuccessful courtship occurred many times (usually the result of a male not performing the sideways gait), a female would always acquiesce at the next courting. After performing the sideways gait, a male ran up to a female's side, about midway along her length; a male approached a female almost perpendicularly from her side. If features on the substrate made a male's approach difficult, his contact with a female was as perpendicular to her as the substrate permitted. When a male ran up to a female, he touched her briefly (less than a second) with both his antennae. A male's antennae usually struck a female's thorax or head and the distal end of her forewing because his antennae were



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Figure 1. Schematic diagram depicting precopulatory behavior in Trichadenotecnum alexanderae. Typical behavior is indicated by bold %
face arrows. Female behavior coinciding with male behavior is indicated by dashed arrows. \å£ 0




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19831 Betz - Biology of' Trichacienotecnum 101 usually held about 90' apart and at about 45' off the substrate at rest and also during the search for a female. Directly after contact- ing her, a male backed away slightly, then rapidly fanned his wings over his body. The wings were fanned at such a rapid rate and at such a small angle (never more than 90') that they became blurred. As a male continued to fan his wings, he began to move anteriorly along a female's side, while still remaining perpendicular to her. A male continued this motion until he was almost facing a female. When this occurred, a male stopped fanning, dropped his wings slightly, turned about 180å¡ and backed underneath a female between her legs. The genitalia were apposed in this manner. Occasionally a male stopped fanning when he was only laterally apposed to a female's head, then turned about 90å¡ and tried to back under her. Of the 14 mounting attempts I observed progressing in this way, only two of them led directly to copulation. Of the failed attempts, eight were unsuccessful because males were blocked from backing in by females' legs; in the remaining four attempts, males turned around farther than necessary and kept moving backward beside the females rather than beneath them. When a female remained hidden from a male's view, he some- times approached her directly from the front (N = 3). In two encoun- ters, the female assumed the receptive posture (see below) as the male fanned his wings. However, both of these males were unable to locate the female after they turned around and began to move backwards. One of the males approached the female on her left, turned counterclockwise about 240å¡ and finally stopped after mov- ing 8 mm away from her. He then tried to mount her end-to-end (i.e., facing away from her), but this failed. The pair remained motionless in the end-to-end position for about 30 seconds with their genitalia nearly touching, then the male courted the female from her side and was able to orient himself correctly. The male of the third encounter courted frontally, but the female turned her body slightly instead of assuming the receptive posture, and the male was unable to move far enough backward for their genitalia to come together. The courtship did not lead to copulation. Most (73.7%) courting attempts were successful on the first try (Table 1, A). When an attempted mounting failed, a male and female always remained motionless for about 10-30 seconds. After this period, if a male and female remained within about 1 cm after



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102 Psyche [VOI. 90
Table 1. Precopulatory behavior in Trichudenoiecnum ulexanderue Number of courting attempts
by a male (including the one
leading to copulation)
% of Total
I. One 73.7
2. Two 15.2
3. Three 10.1
4. Four 0.0
5. Five 1 .O
B. Length of time between the
introduction of a male
and the beginning of mating
(i.e., genitalic contact)
C. Stage in courtship when a female
assumed the receptive posture
I. During the approach of a male
2. When touched by a male's antennae
-
x
s.d.
range
N
3. Just before a male backed underneath
1.1
N =96 100.0
I. 1 minutes
1.3
0.1-9.0 minutes
62
he number of mating pairs for which the states of this behavioral character were recorded.
they separated, a male courted again by approaching a female on her side, touching her with his antennae, and fanning his wings. Once either sex had fled from an unsuccessful courtship. males always began further courtship with a sideways gait. I observed the behavior of females that had fled from a failed courtship (N = 4). Each female eventually stopped moving, and at this time I observed each female flexing her valvulae dorsoventrally in a pairwise manner, and making about ten contractions of her abdomen.
The time required by males to establish genitalic contact after they were introduced to females varied among mating encounters (Table 1, B). This period was usually less than 1 minute if the first courtship was successful. A male ran directly to a female in some encounters, and the time between introduction and the beginning of copulation was usually less than 30 seconds. Some males (N = 5) were slower to find females because each remained within a small



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area on a female's bark. Even though a female was not nearby, three males exhibited sideways gaiting, wing fanning, and backward move- ment, while two others only displayed a higher level of activity. All five males were active, and each found a female about 10 minutes after introduction to the female's bark. A female had to raise the anterior part of her body for a male to be able to fit beneath her. Females always assumed a characteristic appearance for this purpose that I here term the receptive posture. In the receptive posture, the fore- and midlegs were moderately extended, the hindlegs were slightly extended, and the antennae were swept back along a female's body (Fig. 2b). Most (83.3%) females assumed the receptive posture when males touched them with their antennae (Table 1, C). Some (1 5.6%) females assumed the receptive posture when males performed the sideways gait. One female waited until a male was backing underneath her. Females assuming the receptive posture early in courtship (i.e., before antenna1 contact was made by a male) elicited less wing fanning from males. Males exhibited all of the actions involved in courtship, but performed them more rapidly. On the other hand, the female not assuming the receptive posture until a male began to move beneath her did not appear to inhibit the male from courting normally.
After a courtship failed, a male often fanned his wings around a female for a longer period of time during the next one, regardless of whether a female assumed the receptive posture when a male was approaching or courting (N= 10). These prolonged courtships always led to copulation.
A male had to crouch slightly just prior to moving beneath a female, even though she had assumed the receptive posture. This position is shown in Figure 2a. Males remaining in a standing posi- tion were blocked from moving past the coxae of the females' legs (N = 2). Furthermore, at this time a male's abdomen became slightly arched along its length, raising the posterior end. A male's wings were kept extended over his body as he backed underneath a female, and she rested her fore- and midlegs on him. When the genitalia of a pair were apposed, the head of a female was positioned between and slightly caudad of a male's raised hindwings. As a male moved under a female, the shelf of his epiproct, which normally rested in a posterodorsal position, struck a female's sterna



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Psyche
[Vol. 90
Figure 2. Typical precopulatory behavior in Tric/~u~/wotecnum alexaniferae. a: A male in position to move beneath a female. b. The receptive posture of a female.
and was brought anteriorly. This flattened the shelf against the male's abdominal terga, and caused his paraprocts to extend slightly posteriorly. When fully beneath a female, a male's epiproctal shelf was brought into apposition with the basal arms of a female's sub- genital plate and the sterna of her posterior abdomen. 1 studied how males orient themselves with females to produce a successful mounting. Individual females (N = 18) that had been freshly killed (by pressure from a forceps) from a Lake of the Woods culture were placed in a standing position on the substrate. Males always courted and mounted the females without losing orientation (N = 5). When 1 reoriented a female while a male was turning around after touching her with his antennae, he did not reorient to mount successfully (N = 3). If a female was moved as a male approached (that is, prior to antennal contact), a male was always able to orient and mount in the proper direction (N = 10). Hence, antennal contact by males appeared to be important for a successful mounting.
When I placed a teneral male with a receptive female (N = I), he ran to her, paused briefly at her side, but then did not exhibit any other courting behavior (e.g., antennal contact, wing fanning, etc.). Instead, he repeatedly climbed over her for about 10 seconds until she fled. The male made no attempt to mount, and the female did not assume the receptive posture.




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Copulatorj Behavior
When a male was fully beneath a female, the posterior end of his abdomen probed for hers. The valvulae of a female dropped ventrally somewhat, and moved until contact was made with a male. The genitalia ofmale and female T. alexanderae interlocked strongly together during copulation.
When their genitalia became locked, a male lifted a female off the substrate by extending his legs, which were still crouched from back- ing beneath her.
A normal copulatory position for a pair of T. alexanderae is shown in Figure 3. The hind legs of most (67.8%) males were extended slightly more than the other pairs of legs, causing a male's head to be lowered, and raising and slightly arching his abdomen (Table 2, A). Males greatly extending their hindlegs usually also had greatly arched abdomens; males extending all pairs of legs about -
1.0 mm
Figure 3. Trir/iuilenotecnum alexanderae in copulation.



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106 Psyche [VOI. 90
equally had no abdominal arch. Because the degree of abdominal arching and the extension of the legs compensated for each other, the overall position of a male, and thus the relative positions of a male and female, generally differed little among the matings I observed. A male's abdomen became slightly more arched and his head dropped lower as copulation progressed. Some males lowered their heads so much during copulation that their maxillary palps touched the substrate.
After a female was raised off the substrate, a male's abdomen contracted more or less rhythmically. A female contracted her abdomen in synchrony with a male. Her paraprocts were periodi- cally flexed medially during copulation. At the beginning of copulation, the wing pairs of a male were usually extended high over his body, forming a small angle between them (Table 2, B). As copulation progressed, the angle formed by the wing pairs increased; the angle of the wings at the end of copula- tion was about 60å greater (Table 2, C). I found 45.7% of all males had both wing pairs locked at the nodus (Table 2, D). Wing pairs remaining free were in a position as though they were locked, and thus did not interfere with copulation.
Table 2 (E and F) shows that a male's antennae generally remained in a normal resting position during copulation. A female was lifted off the substrate until the angle formed by her body and the substrate was about 3 lo-60' (Table 2, G). Females whose bodies inclined more than 60å (7.4%) had been pushed up into this position when males mounted beneath them. A female placed her fore- and midlegs on a male when he moved beneath her. Table 2 (H and I) shows the distribution of the place- ment of a female's fore- and midlegs, respectively. Most (41.3%) forelegs were placed on males' hindwings and most (50.0%) midlegs were placed on males' anterior abdominal pleura. However, as reflected in Table 2, the first two pairs of legs were positioned in many other ways.
Table 2 (J) shows the distribution of the placement of a female's hindlegs. Most (93.3%) females kept their hindlegs on the substrate. The rigidity of the hindlegs indicated that they were supporting some of a female's weight.
The forewing tips rested lightly on the substrate in 84.8% of the females (Table 2, K). This contact did not appear to support much of a female's weight.




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Table 2. Copulatory behavior in Trii~/iuitem)iecnuni ulemnderue % of Total
Position of u male
A. Extent of the arch of
the abdomen
I Not arched 21.9
2. Slightly arched 67.8
3. Greatly arched 10.3
B. Angle formed by the forewings
at the beginning of mating I 0'-30' 52.3 2. 31'-60' 38.5
3. 61'-90' 6.1
4. 91'-120' 3.1
N=65
Angle formed by the forewings
at the end of mating
I 0'-30'
2. 31'-60'
3. 61'-90'
4. 91'-120'
5. 121'-150'
6. 151'-180'
7. 181'-210'
D. Number of wing pairs locked
at the nodus
E. Angle formed by the antennae
1. None
2. One
3. Both
N=58 100.0
F. Angle formed by the antennae
and the bark substrate I. 0'-30' 40.5
2. 31'-60' 59.5




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108 Psyche [VOI. 90
Table 2. (continued)
% of Total
Position uf afemale
G. Angle formed by the body of a
female and the bark substrate 1. 0'-30' 1.90 2. 31'-60' 90.7
3. 61'-90' 7.4
H. Placement of a foreleg on a male
1. Forewing
2. Base of forewing
3. Hindwing
4. Base of hindwing
5. Metanotum
6. Anterior abdominal
terga
7. Anterior abdominal
pleura
8. Hind tibia
I. Placement of a midleg on a male
I . Hindwing
2. Hindwing base
3. Metanotum
4. Anterior abdominal
terga
5. Anterior abdominal
pleura
6. Anterior abdominal
sterna
7. Hind tibia
8. Hind femur
9. Bark substrate
J. Placement of a hindleg on a male
I. Anterior abdominal
pleura 1 .O
2. Anterior abdominal
sterna 0.5
3. Hind tibia 5.2
4. Bark substrate 93.3




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19831
Betz - Biologj of Trichadenotecnum
Table 2. (continued)
% of Total
Position of a female
K. Position of the forewing tips 1. On the bark substrate 84.8 2. In the air 15.2
Angle formed by the antennae I. O0 -30' 25.0 2. 31'-60' 5 1.7
3. 61'-90' 18.3
4. 9l0-120' 5 .O
N=60 100.0
M. Angle formed by the antennae and