Description of the Spider Masoncus pogonophilus (Araneae, Linyphiidae), a Harvester Ant Myrmecophile

5 Pages·1995·5.2 MB·English

by  Paula E Cushing

1995. TheJournal ofArachnology 23:55-59
DESCRIPTION OF THE SPIDER
MASONCUSPOGONOPHILUS (ARANEAE, LINYPHIIDAE),
A HARVESTER ANT MYRMECOPHILE
Paula E. Cushing: Department ofZoology, University ofFlorida, Gainesville, Florida
32611 USA
ABSTRACT. OnespeciesofthegenusMasoncus(Araneae,Linyphiidae)isdescribedandillustrated.Masoncus
pogonophilus new species has been collected exclusively inside the nests ofthe Florida harvesterant, Pogono-
myrmexbadius(Latreille)(Hymenoptera,Formicidae)andis,therefore,consideredamyrmecophile,orobligate
ant associate. Morphological characters separating this new species from two ofthe three described congeners
(M. arienus andM. conspectus are noted.
)
Three species are included in the genus Ma- pitsandastraight,distallybifidembolicdivision
soncus Chamberlin 1948: M. arienus Chamber- in the males (see genus description below).
lin 1948, M. duxChamberlin 1948, andM. con- In the species description that follows, I use
spectus (Gertsch & Davis 1936) (synonymized primarily carapace, genitalic, chaetotaxic, nu-
withM. nogalesChamberlin 1948byIvie 1967). meric,andpalpalcharactersdeemedmostuseful
ThefemaleholotypeofM. duxhasbeenlostand by Millidge (1980) for erigonine spiders. These
Iwasunabletolocate anyspecimensofthisspe- characters include: 1) the overall conformation
cies. The female holotype, male allotype and of the male palpal organ, 2) the shape of the
paratypes of M. nogales designated by Cham- embolic division, 3) the external appearance of
berlin (1948) have also been lost. However, the the epigynum, 4) the number of dorsal tricho-
holotype of Tapinocyba conspecta is housed at bothriapresentonthe palpaltibia ofboth sexes,
theAmericanMuseumofNaturalHistoryinNew 5)thenumberofdorsaltibial spinespresent(ex-
YorkCity, NewYork(AMNH) asare otherrep- pressed by the formula a:b:c:d), 6) the number
resentatives of this species. The holotype and of dorsal metatarsal trichobothria present (ex-
paratypes of M. arienus designated by Cham- pressedbytheformulaI:II:III:IV), 7)therelative
berlin (1948) are also at AMNH. One male rep- positionofthedorsalmetatarsaltrichobothrium
resentative ofM. arienus is housed at the Cali- on leg I (expressed by the formula Tml = dis-
fornia Academy of Sciences in San Francisco, tance from tibia-metatarsusjoint to trichoboth-
California (CAS). rium/distance from tibia-metatarsus joint to
No information was recorded either in the metatarsus-tarsus joint), and 8) the relative
original species descriptions or on the collecting stoutness of tibia I (expressed by the formula
labelsoftheexistingspecimensregardingthenat- Tibi = length oftibia/width oftibia viewed lat-
uralhistoryofthedescribedspecies. M. duxwas erally). Overall body size, body color, and num-
describedfromasinglefemalecollectedinnorth- ber ofsetae on the carapace are also given. Cer-
ern Manitoba, Canada. All specimens ofM. ar- tain ofthese characters as well as others used in
ienus were collected in Arizona. M. conspectus Chamberlin’s (1948) descriptions or obvious on
was described from the male holotype and two the existing specimens are ofparticular value in
maleparatypescollectedinTexas. Otherrecords separating M. arienus, M. conspectus and M.
,
ofthis species include Arizona and Florida (the pogonophilus (Table 1). All measurements were
latter collected by the shores ofNewnan’s Lake takendirectlyfromthespecimensusinganocular
in Alachua County). micrometer in a dissecting microscope. Mea-
Masoncuspogonophilus new species was orig- surements were rounded to the nearest 0.1 mm.
inallycollectedby SanfordPorterfrom thenests
of the Florida harvester ant, Pogonomyrmex Masoncus Chamberlin 1948
badius (Latreille) (Hymenoptera, Formicidae) The type species ofthe genus is M. arienus.
(Porter 1985). It is included in the genus Ma- The genus Masoncus is characterized by both
soncus due to the presence of distinct cephalic cephalic pits in the males and a straight, distally
55
THEJOURNALOFARACHNOLOGY
56
Table 1.—MorphologicalcharactersmostusefulinseparatingthreeoffourMasoncusspecies. (Allspecimens
ofM. duxarelost, andthespeciesdescriptionisbasedsolelyonthefemaleholotype.)pme = posteriormedian
eyes.
Characters M. arienus M. conspectus M. pogonophilus
Location ofcephalicpits Pit opens backofposted- Pitopens and extendsbe- Pitopens andextendsbe-
in males oreyes; notextending neath pme neath pme
underpme
Cheliceral spurs towards Presenton males and fe- Present on males; reduced No cheliceral spurs on
distal end males tovery small black males orfemales
spurs on females
Setigerous nodule orspur Nodule present on males Spuron males; lackingon No setigerousnodule or
anteriorto fanggroove and females females spuron males orfe-
males
Enditeswith small spur Present on males and fe- Presenton males and fe- No spurs on enditesof
on ectal side oftip males malesalthough less dis- males orfemales
tincton latter
Shape ofpalpal tibia Widely spaced black- Closely spacedblack- Moderately spacedblack-
tippedprocesses on dis- tipped processes on dis- tipped processeson dis-
tal edge flush w/ surface tal edge extending tal edge flush w/ surface
oftibia; long setal slightlyaway from sur- oftibia; longsetal
fringe on lateral edge face oftibia; long setal fringe on lateral edge
fringe on lateral edge (see fig. 4)
(fig. 97 in Chamberlin
1948)
Embolic division Bifurcation begins close to Distally bifidw/ proximal Distally bifidw/ proximal
tail-piece; each segment part ofbifurcation bent partofbifurcation bent
ofbifurcationcoiled forwardandextending forwardandextending
(fig. 101 in Chamberlin overmost distal part overmostdistal part
1948) which is, itself, squared which is, itself, bifur-
off(fig. 98 in Chamber- cated (see Fig. 3)
lin 1948 shows it point-
ed)
bifid embolic division (Chamberlin 1948) (dia- description. The collecting information as well
gram oflinyphiid palpal structures in Millidge asthefuturemuseum destinationforthesepara-
1980). types are presented in Table 2.
Etymology.—The specific epithet is derived
fromthegenericnameofthehostantwithwhich
Masoncuspogonophilus new species
the spider is found.
(Figs. 1-5) Holotype.—Total body length: 1.7 mm. Car-
Type.—The male holotype was collected 23 apace length: 0.9 mm. Carapace width: 0.7 mm.
cm below ground inside a nest chamber ofthe Colors: carapace orange; abdomen grey; legs or-
Florida harvesterant, Pogonomyrmexbadius in ange; sternum orange. Number of setae along
ArcherSandhills, 1.4kmwestoftheLevyCoun- midlineofcarapace: three. PalpasinFig. 3. Em-
tyline offofState Road 24. The female allotype bolic division as in Fig. 4. Number of tricho-
was collected from the same P. badius nest. She bothria on palpal tibia: two (Fig. 2). Number of
was found in a nest chamber 46.5 cm below dorsal tibial spines: 1:1:1:1. Number of dorsal
ground. Both were collected on 25 September metatarsaltrichobothria: 1:1:1:0.Tml:0.82.Tibi:
1994 and both will be deposited in the arach- 7.0.
nological collection at CAS. Males(general).—{n— 12).Totalbodylength:
Theholotype, 11 maleparatypes, theallotype, 1.6-2.1 mm (x = 1.8 ± 0.14). Carapace length:
and 12femaleparatypeswereusedinthisspecies 0.8=0.9 mm (x = 0.9 ± 0.04). Carapace width:
CUSHING-DESCRIPTIONOFMASONCUSPOGONOPHILUS(LINYPHIIDAE) 57
Figures 1-5. -Masoncuspogonophilus new species. 1, male carapace, dorsal view (scale = 0.4 mm); 2, tibia
and patella ofleft male palpus, dorsal view, trichobothria in circular pits (scale = 0.2 mm); 3, male palpus,
prolateral view (bifurcation ofembolic divisionjust visible distally) (scale = 0.2 mm); 4, embolic division of
leftmale palpus, mesoventral view(scale = 0.1 mm); 5, epigynum, ventral view (scale = 0.1 mm).
0.6-0.8 mm (x - 0.7 ± 0.05). Colors: carapace chobothria: 1:1:1:0. Tml: 0.82-0.88 (x = 0.84 ±
yellow-orangetoorange; abdomengrey; legsyel- 0.02). Tibi: 6.5-7.? (x = 7.0 ± 0.35).
low-orange to orange; sternum yellow-orange to Females.—(n = 13). Total body length: 1.5-
orange. The color seems to fade severely when 1.9 mm (x = 1.8 ± 0.13). Carapace length: 0.8-
specimens are kept in isopropanol rather than 1.2 mm (x = 0.9 ± 0.11). Carapace width: 0.6-
ethanol. Number ofsetae along midline ofcar- 0.9 mm (x = 0.7 ± 0.09). Colors: sameasmales.
apace (Fig. 1): variable, 2-4 (setae easilybroken Numberofsetaealongmidlineofcarapace: vari-
in preservation). Palp as in Fig. 3 Embolic di- able, 2-5; females also had smaller setae scat-
.
vision as in Fig. 4. Number oftrichobothria on tered on either side ofmidline. Epigynum as in
palpal tibia: generally two (Fig. 2), however one Fig. 5. Number oftrichobothria on palpal tibia:
male had two on the left palpal tibia and three generallythree, howeverone female had two on
on the right and another had three on the left bothpalps, threeotherfemaleshadthree tricho-
and two on the right. Number of dorsal tibial bothria on the left palpal tibia and two on the
spines: 1:1:1:1. Numberofdorsal metatarsaltri- right. Number ofdorsal metatarsal trichoboth-
.
58 THEJOURNALOFARACHNOLOGY
Table 2.—Collection informationand museum destination forthe 23 paratypes. Allwere collectedfrom the
nests ofthe Florida harvester ant, P. badius. MCZ = Museum ofComparative Zoology, Cambridge, Massa-
chusetts; DPI = Division ofPlant Industry, Gainesville, Florida; AMNH = American Museum ofNatural
History, NewYork, NewYork; CAS = CaliforniaAcademyofSciences, San Francisco, California.
Number
Collection ofspec-
date Florida county Collector imens Museum
Males
10-XI-1982 Leon S. D. Porter 1 MCZ
9- XI-1984 Leon S. D. Porter 1 MCZ
13- 1-1990 Walton Skelley, Tumbow &Thomas 2 DPI
14- 1-1990 Okaloosa Skelley, Tumbow &Thomas 1 DPI
9- ¥-1992 Leon P. E. Cushing 1 DPI
AMNH
26- ¥-1992 Levy P. E. Cushing 2
AMNH
8- X-1992 Levy P. E. Cushing 1
20- 11-1993 Levy P. E. Cushing 1 CAS
25- IX-1994 Levy P. E Cushing 1 CAS
Females
3- 1-1990 Okaloosa P. Skelley 1 DPI
13- 1-1990 Walton Skelley, Tumbow& Thomas 1 DPI
9- ¥-1992 Leon P. E. Cushing 1 DPI
AMNH
28- 11-1993 Putnam P. E. Cushing 4
25-VII..j.993 Putnam P. E. Cushing 1 MCZ
25- IX-1994 Levy P. E. Cushing 4 CAS
ria: 1:1:1:0. Tml: 0.58-0.87 (x = 0.81 ± 0.09). distally bifid with the proximal part ofthe bi-
Tibi: 6.5-7.9 (X = 7.1 ± 0.38). furcation bent forward and extending over the
Diagnosis.—The carapace ofmale M. pogon- most distal part ofthe bifurcation. However, in
ophiiusmostresemblesthatofM. conspectus(fig. M. pogonophilus the most distal part ofthe bi-
93 in Chamberlin 1948 and Fig. 1). In both spe- furcationis,itself,bifurcated,whereasinM. con-
cies, the cephalic pits extend beneath the pos- spectusit is flattened (although fig. 98 in Cham-
terior median eyes (pme) whereas in M. arienus berlin 1948showsittobepointed).InM. arienus
the cephalic pits open behind the pme. The em- the embolic division is also bifid, but the bifur-
bolicdivisionofmaleM.pogonophilusnewspe- cationbeginsveryclosetothetailpieceandeach
cies most resembles M. conspectus (fig. 98 in segment ofthe bifurcation is coiled (see fig. 101
Chamberlin 1948 and Fig. 4) in that both are in Chamberlin 1948). The male palpal tibia of
the new species, as with M. conspectus and M.
arienus, is fringed laterally with long setae (Fig.
2). Chamberlin 1948 (fig. 102) does not show
this fringe ofsetae on his drawing ofM. arienus
butitisevidentonthepreserved specimens. All
threespecieshavetwoblack-tippedprocesseson
the distal edge ofthe palpal tibia (Fig. 2). These
processes are more widely spaced in M. arienus
than in either M. conspectus or in M. pogono-
philus. The black-tipped process inM. conspec-
tus is found on a slight ridge that extends away
from the surface ofthe tibia (fig. 97 in Cham-
berlin 1948). Interestingly, M. conspectus is the
only one ofthe three previously described con-
Figure 6.—Sticky silk from adult male Masoncus geners whose known distribution extends into
pogonophilus newspecies web. Magnification 400x northern Florida. The new species can be sepa-
CUSHING-DESCRIPTIONOFMASONCUSPOGONOPHILUS(LINYPHIIDAE) 59
rated from the congeners based primarily upon Juveniles are present inside the ant nests during
characters described in Table 1 as well as upon all months ofthe year (Porter 1985; pers. obs.).
overall size; the new species being somewhat Porter reported a 4:1 female-biased sex ratio
smaller than M. dux, M. arienus and M. con- among the spiders, while I have found an even
mm
spectus, which are all between 2.10-2.65 in more extreme 7.5:1 female-biased ratio. Due to
length according to Chamberlin (1948) and the scarcity ofeggsacs and the small number of
Gertsch & Davis (1936). eggs per eggsac, it has not been possible to de-
NaturalHistory.—Masoncuspogonophilusnew termine whetherthis is a primary sex ratio bias.
species lives within the nest chambers of the ACKNOWLEDGMENTS
Florida harvester ant, P. badius. It is about lA
the size ofits 7-9 mm long host and feeds on I am grateful to Mark Stowe, Susan Moegen-
m
collembolans found throughout the 1-3 deep burg, John Arnett, Joyce Thomas, Barbara C.
subterranean nests (Porter 1985). The ant nest Dixon,MichaelE.Morgan,andRebeccaForsyth
provides a stable microclimate as well as an for their help in collecting specimens. Thanks
abundantfoodsourceforthespider. Thespiders also to Drs. Jonathan Reiskind, Sanford Porter,
have never been collected outside the ant nests CharlesDondale,andCharlesGriswoldfortheir
andareextremelysusceptibletodesiccationwhen helpful comments on drafts ofthis manuscript.
removedfromthenests. Theyappear, therefore, Thanksalsoto CAS, AMNH, DPI and MCZfor
tobeobligateantsymbionts, ormyrmecophiles. loaning specimens. This workwas supported by
Immigration to new nest sites is common in a Grinter Fellowship from the University of
P. badius(Gentry& Stiritz 1972; Golley& Gen- Florida and a Theodore Roosevelt Grant from
try 1964; Gordon 1992). While observing three the American Museum ofNatural History.
suchcolonymigrations,eachoccurringeitherjust
LITERATURECITED
after a summer shower or in the early morning
when the surface temperature was cool and the Chamberlin,R. V. 1948. OnsomeAmericanspiders
humidity high, I saw spiders and collembolans ofthefamilyErigonidae.Ann.Entomol.Soc.Amer-
atmhoePviCrinhRogsf(tpraoonlmtystmhweeirtoahlsidencctohhleaoinenymisrgietraeactttoiiotohnne)t-rnabeialwss.eadUmsimidons-gt GeniFtclrao,yr,i4d1Ja.:4hB8a.3r-v&5es6Kt2.e.rLa.ntS,tiPriotgz.ono19m7y2r.meTxhebardoiluesoifnotlhde
field mineral nutrient relationships. Environ. En-
lecular technique, I have also found evidence tomol., 1:39-41.
that spiders disperse between neighboring ant Gertsch,W.J.&L.I.Davis. 1936. Newspidersfrom
nests (pers. obs.). Texas. American Mus. Novit., 881:1-21.
BothsexesofM.pogonophilusbuildpreycap- Golley, F. B. &J. B. Gentry. 1964. Bioenergetics of
turewebsinthelab, and Ihave seenwebsinside thesouthernharvesterant, Pogonomyrmexbadius.
the ant nest chambers. Both males and females Ecology, 45:217-225.
producestickysilk(Fig. 6).Therefore,malespre- Gordon, D. M. 1992. Nest relocation in harvester
ants. Ann. Entomol. Soc. America, 85:44-47.
sumably retain the aggregate and flagelliform
Ivie,W. 1967. SomesynonymsinAmericanspiders.
glands into adulthood; most adult male spiders J. NewYork Entomol. Soc., 75:126-131.
lose these glands during the terminal molt and Kovoor, J. 1987. Comparative structure and histo-
cannotsubsequentlyproducestickysilk(Kovoor chemistryofsilk-producingorgansinarachnids.Pp.
1987). Maintainingthe ability to produce sticky 160-186,InEcophysiologyofSpiders.(W.Nentwig,
silk as adults may be common among male er- ed.). Springer-Verlag, Berlin.
igonine Linyphiids as I have observed such be- Millidge,A. F. 1980. TheerigoninespidersofNorth
haviorsamongother(unidentified) male erigon- America.Part 1. Introductionandtaxonomicback-
ines. ground(Araneae: Linyphiidae). J. Arachnol., 8:97-
FemaleM.pogonophiluslay 1-6eggsinadisk- 107.
shaped eggsac deposited in a depression in the Porter, S. D. 1985. Masoncus spider: a miniature
wall ofa nest chamber (n = 9 eggsacs, x = 2.9 predator of Collembola in harvester-ant colonies.
Psyche, 92:145-150.
± 1.5 eggs/eggsac). The eggsac is flush against
thesurfaceofthechamberwalls.Juvenilespiders Manuscriptreceived4December1994, revised6March
molt once inside the eggsac and pass through 1995.
threeadditional moltsbefore reachingmaturity.