The spider fly Acrocera bakeri Coquillett, 1904 (Diptera: Acroceridae) is reported as a new state record for Wisconsin. This is a major range extension, because this rarely-encountered species was previously known only from the western U.S., specifically Arizona, California, and Nevada. The taxonomic history of the species is briefly discussed and hypotheses are offered for its unexpected presence in Wisconsin

Kelly, Sandor L

Woller, Derek A.

Young, Daniel K

English

Valparaiso University

The Great Lakes Entomologist Volume 48 Numbers 3/4 -- Fall/Winter 2015 Numbers 3/4 -- Fall/Winter 2015 Article 5 October 2015 Comments on a Major Range Extension of the Little-Known Acrocera bakeri (Diptera: Acroceridae) Derek A. Woller Texas A&M University Sandor L. Kelly University of Central Florida Daniel K. Young University of Wisconsin, dkyoung@wisc.edu Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Woller, Derek A.; Kelly, Sandor L.; and Young, Daniel K. 2015. "Comments on a Major Range Extension of the Little-Known Acrocera bakeri (Diptera: Acroceridae)," The Great Lakes Entomologist, vol 48 (3) Available at: https://scholar.valpo.edu/tgle/vol48/iss3/5 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. 132 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4Comments on a Major Range Extension of the Little-Known Acrocera bakeri (Diptera: Acroceridae)Derek A. Woller1, Sandor L. Kelly2, and Daniel K. Young3*AbstractThe spider fly Acrocera bakeri Coquillett, 1904 (Diptera: Acroceridae) is reported as a new state record for Wisconsin. This is a major range extension, because this rarely-encountered species was previously known only from the western U.S., specifically Arizona, California, and Nevada. The taxonomic history of the species is briefly discussed and hypotheses are offered for its unexpected presence in Wisconsin. ____________________Acroceridae, commonly referred to as spider flies, is a fascinating and understudied family within the insect order Diptera. Based on personal obser-vations and correspondence, and as indicated by recent descriptions of species and genera (Winterton 2012, Schlinger et al. 2013), the family is also not well-represented in collections. The life histories of its species are intriguing as well in that the larvae are spider parasitoids that exhibit hypermetamorphic develop-ment (distinctly different larval stages: Schlinger 1987). Based on the examina-tion of numerous specimen data labels, trapping (especially with Malaise traps) appears to be one of the most effective methods of capturing these cryptic flies. While examining and identifying acrocerids on loan from the University of Wisconsin Insect Research Collection (WIRC) in Madison, WI, two male speci-mens quickly stood out from the remainder. These specimens were determined to be Acrocera bakeri Coquillett, 1904 (Diptera: Acroceridae) (Fig. 1A–D). Not only does this discovery constitute a new state record for Wisconsin, it also sug-gests the range of A. bakeri is considerably wider and much farther east than previously known. Prior to this, A. bakeri had been considered a western U.S. species, having been recorded only from the western U.S. states of Arizona, California, and Nevada (Coquillett in Baker 1904, Sabrosky 1948).  Herein, we report this new record, discuss potential reasons for the extension of its range, and include figures of the species.Materials and MethodsDigital images of one specimen were taken in the Song Laboratory of Insect Systematics and Evolution at the University of Central Florida (UCF) (recently relocated to Texas A&M University) using a Visionary Digital BK Plus Imaging System in combination with a Canon EOS 7D camera and 65mm lens (often coupled with a 1.4x magnifier) to take multiple images at different focal lengths. The re-sulting files were converted from RAW to TIFF format using Adobe Lightroom 3.2 1Song Laboratory of Insect Systematics and Evolution, Department of Entomology, Texas A&M University, College Station, TX, U.S.A. (e-mail: asilid@gmail.com).2University of Central Florida Collection of Arthropods (UCFC), Department of Biology, University of Central Florida, Orlando, FL, U.S.A. 3 Department of Entomology, University of Wisconsin, Madison, WI. U.S.A.* Corresponding author: (e-mail: dkyoung@wisc.edu).1Woller et al.: Comments on a Major Range Extension of the Little-Known AcroceraPublished by ValpoScholar, 20152015 THE GREAT LAKES ENTOMOLOGIST 133Figure 1. Acrocera bakeri male. (A) Habitus, lateral view; (B) Habitus, dorsal view, displaying characteristic abdominal pattern; (C) Head, anterior view; (D) Left wing, dorsal view. Composite Digital Images: D.A. Woller.and then stacked into a single composite image using Zerene Stacker (v.1.02). Next, Adobe Photoshop CS5 Extended was used to add a scale bar and adjust light levels, background coloration, and sharpness.The habitat image (Fig. 2) was taken using a Canon EOS Rebel T2i digital camera and depicts the specific locality where the acrocerids were captured in a Malaise trap. This site is dominated by large-toothed aspen, Populus grandidentata Michaux, within the confines of Quincy Bluff in southcentral Wisconsin (TNC 2015). Originally purchased by The Nature Conservancy, Quincy Bluff and Wetlands has recently been turned over to the Wisconsin Department of Natural Resources for its management. The bluff area is largely managed as an oak-pine savanna with smaller prairie restorations, although numerous sites within the acreage have significant aspen stands. Malaise traps have been running for sev-eral years in aspen, mixed oak (Quercus spp.), and jack pine (Pinus banksiana Lambert) habitats, but the acrocerids discussed here were recovered solely in the aspen or oak-aspen habitat.The specimens were field collected into 70–80% ethanol. However, since most Diptera are prone to excessive tissue distortion during the normal dehydration process associated with pinning, the HMDS technique (Nation 1983) was used in specimen preparation to minimize exoskeletal collapsing and shriveling.Two male specimens were examined from the same locality: U.S.A.: WI: Adams Co., Quincy Bluff TNC, 43.86627, -089.88363 [WGS84], collected by Daniel K. Young, ex: Malaise in Populus grandidentata blow. One specimen was collected 13–21 July 2011 and the other 26 July–1 August 2011. Both specimens are deposited in the WIRC.2The Great Lakes Entomologist, Vol. 48, No. 3 [2015], Art. 5https://scholar.valpo.edu/tgle/vol48/iss3/5134 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4Results and DiscussionThe taxonomic history of A. bakeri is convoluted. Prior to Sabrosky (1948), males of A. bakeri and Acrocera melanderi Cole, 1919 were comingled with a third species: Acrocera bulla auctorum multorum, non Westwood, 1848, which was named and described as Acrocera steyskali Sabrosky, 1944 due to his (and previous authors’) disagreement with the original description in relation to specimens in their possession. Sabrosky (1948) did not indicate specifically how A. melanderi and A. steyskali differ, because he wanted to first examine the type of A. melanderi. However, he suspected that A. steyskali might be a junior synonym of A. melanderi, a suspicion confirmed by Schlinger’s (1965) synonymization of the two species. Regarding A. bakeri and A. steyskali, Sabrosky (1948) commented that males were superficially similar while females were quite different. His couplet that separates the two species, his comments regarding the males of A. bakeri, and his citing of figures from an earlier work (Sabrosky 1944) indicate that the general abdominal color pattern (Fig. 1B) is the primary character separating the males of the species. Although Sabrosky (1948) insisted this patterning was enough to consider A. bakeri a unique species, it should be noted that he possessed only nine specimens, seven of which were males. Furthermore, A. bakeri was originally described from a single female from Nevada (Coquillett in Baker 1904), while all other known specimens are from Arizona and California (Sabrosky 1948). We know first-hand that acquiring acrocerid material is generally difficult, which, as outlined above, can cause taxonomic issues. Thus, at first, it does seem Figure 2. Aspen stand habitat where both male specimens of Acrocera bakeri were recovered from a Malaise trap (image taken 29 September 2014).   Digital Image: D. K. Young.3Woller et al.: Comments on a Major Range Extension of the Little-Known AcroceraPublished by ValpoScholar, 20152015 THE GREAT LAKES ENTOMOLOGIST 135remarkable that this hitherto western species has been found in a state so far to the northeast, so we offer the following hypotheses to explain this new locality. First, it is feasible that the Wisconsin specimens represent a new species based largely on the geographic location. We are hesitant to follow this hypothesis, because over-splitting in Acroceridae is not unknown, especially in Acrocera and Ogcodes (Kehlmaier and Almeida 2014, C.J. Borkent personal communication), and we still have very few specimens. C.J. Borkent (personal communication) has suggested that a general lack of geographically-intermediate specimens has often led to over-splitting, as many species have been described from only a few specimens in a small geographic region. Probably, as more specimens are acquired, colors, and even patterns, may exhibit variation across the range. Recently, Kehlmaier and Almeida (2014) utilized molecular and morphological evidence to demonstrate this possibility. They investigated a potential species complex in the European acrocerid, Acrocera orbiculus (Fabricius, 1787), and, although some degree of differentiation was detected in both sets of evidence, they concluded that variation at the genetic level was not significant enough to warrant the recognition of multiple species. They posited that a high degree of phenotypic plasticity was responsible for the observed differences in specimen size and color throughout its range and within populations. A second hypothesis (C.J. Borkent, personal communication) is that the spiders serving as hosts (currently unknown) for larvae of A. bakeri may have moved eastward, whether by human-mediated means or naturally. If it was the latter, then it might imply that these spiders move fairly quickly in terms of time (1948 until now). Alternatively, the flies, and their spiders, may actually have moved westward, and A. bakeri may have simply gone unrecorded in the non-western U.S. until now. Yet another possibility is that either the hosts or their corresponding flies (or both) are actually widespread across the U.S., but the flies are rarely collected. Finally, it is conceivable that these flies and their hosts are now becoming more common, in general, due to a suite of ecological and environmental reasons, like climatic alteration, human-mediated habitat fragmentation, or even host switching. Given the relatively low numbers of ac-rocerids in U.S. insect collections, none of these ideas are improbable and only further collecting efforts will provide support for one to prevail over the others.Since we possessed only two males, we followed the more conservative approach of assigning the Wisconsin specimens to A. bakeri until additional ma-terial or other evidence indicates otherwise. The Wisconsin specimens strongly conform to the pattern concept of Sabrosky (1948), and we see no other obvious features to suggest that these males should be considered a new species.We strongly encourage the continued pursuit of members of this fasci-nating fly family as increased knowledge will only come from the acquisition of more acrocerids; this is not exactly a new idea (Sabrosky 1944), but worth repeating. Quite likely, many collections possess undiscovered acrocerid trea-sures – perhaps contained in the vast unsorted residues of insect traps. Such “insect soup” often sits untouched for years in the average collection due to time and personnel constraints (ABN 2015). We conclude with this invitation: if you encounter unidentified acrocerids and would like them identified (to at least the genus level), we encourage you to contact the first author.AcknowledgmentsWe are very appreciative to Chris Borkent of the California State Collection of Arthropods, California Department of Food and Agriculture for addressing the many acrocerid questions we sent his way, for providing us with interest-ing ideas of his own, and for reviewing an early version of this manuscript. A very special thanks to the third author as well for suggesting the loan in the first place that led to this intriguing find. We thank Jeff Gruber, an Honorary 4The Great Lakes Entomologist, Vol. 48, No. 3 [2015], Art. 5https://scholar.valpo.edu/tgle/vol48/iss3/5136 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4Fellow in the third author’s lab, whose photo of another Acrocera species on-line (Gruber and UW-Madison Dept. of Entomology 2015) caught the eye of the first and second authors and led indirectly to this work. You never quite know what tasty morsels will be found within insect soup, so, by all means, dig in! Finally, we gratefully acknowledge the constructive input from two reviewers of the manuscript.Literature Cited(ABN) Australian Bioinformatics Network.  2015.  Insect Soup Challenge! At the ICCV 2013 International Workshop on Computer Vision for Accelerated Bioscience. Available from http://tinyurl.com/kedtelv (accessed 29 April 2015).  Coquillett, D. W.  1904.  [Description of Acrocera bakeri], p. 23. In C. F. Baker (ed.), Diptera. Reports on Californian and Nevadan Diptera, I.  Invertebrata Pacifica. 1: 17–40.  Gruber, J., and UW-Madison Dept. of Entomology.  Acrocerid — Acrocera bimacu-lata — ♀. Available from http://bugguide.net/node/view/220505#311245 (accessed 29 April 2015).  Kehlmaier, C., and J. M. Almeida.  2014.  New host records for European Acroceridae (Diptera), with discussion of species limits of Acrocera orbiculus (Fabricius) based on DNA-barcoding.  Zootaxa 3780: 135–152.  Nation, J. L.  1983.  A new method using hexamethyldisilazane for preparation of soft insect tissues for scanning electron microscopy.  Biotechnic & Histochemistry 58: 347–351.  Sabrosky, C. W.  1944.  A revision of the American spider parasites of the genera Ogcodes and Acrocera (Diptera, Acroceridae).  American Midland Naturalist 31: 385–413.  Sabrosky, C. W.  1948.  A further contribution to the classification of the North American spider parasites of the family Acroceratidae (Diptera).  American Midland Natural-ist 39: 382–430.  Schlinger, E. I.  1965.  Diptera-Acroceridae, pp. 403–407.  In A. Stone, C. W. Sabrosky, W. W. Wirth, R. H. Foote, and J. R. Coulson (eds.), A Catalog of the Diptera of America North of Mexico.  Agriculture Handbook No. 276.  United States Department of Agriculture, Washington, D.C.  1696 pp.  Schlinger, E. I.  1987.  The biology of Acroceridae (Diptera): true endoparasitoids of spiders, pp. 319–327. In W. Nentwig (ed.), Ecophysiology of Spiders.  Springer Verlag, Berlin.  529 pp.  Schlinger, E. I., J. P. Gillung, and C. J. Borkent.  2013.  New spider flies from the Neotropical Region (Diptera, Acroceridae) with a key to New World genera.  ZooKeys 270: 59–93.  (TNC) The Nature Conservance.  2015.  Wisconsin Quincy Bluffs and Wetlands. Available from http://tinyurl.com/qas5ez9 (accessed 29 April 2015).  Winterton, S. L.  2012.  Review of Australasian spider flies (Diptera, Acroceridae) with a revision of Panops Lamarck.  ZooKeys 172: 7–75.  5Woller et al.: Comments on a Major Range Extension of the Little-Known AcroceraPublished by ValpoScholar, 2015

Comments on a Major Range Extension of the Little-Known Acrocera bakeri (Diptera: Acroceridae)

ValpoScholar

The Great Lakes Entomologist 
Volume 48 
Numbers 3/4 -- Fall/Winter 2015 Numbers 3/4 -- 
Fall/Winter 2015 
Article 5 
October 2015 
Comments on a Major Range Extension of the Little-Known 
Acrocera bakeri (Diptera: Acroceridae) 
Derek A. Woller 
Texas A&M University 
Sandor L. Kelly 
University of Central Florida 
Daniel K. Young 
University of Wisconsin, dkyoung@wisc.edu 
Follow this and additional works at: https://scholar.valpo.edu/tgle 
 Part of the Entomology Commons 
Recommended Citation 
Woller, Derek A.; Kelly, Sandor L.; and Young, Daniel K. 2015. "Comments on a Major Range Extension of 
the Little-Known Acrocera bakeri (Diptera: Acroceridae)," The Great Lakes Entomologist, vol 48 (3) 
Available at: https://scholar.valpo.edu/tgle/vol48/iss3/5 
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. 
132 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4
Comments on a Major Range Extension of the Little-Known 
Acrocera bakeri (Diptera: Acroceridae)
Derek A. Woller1, Sandor L. Kelly2, and Daniel K. Young3*
Abstract
The spider fly Acrocera bakeri Coquillett, 1904 (Diptera: Acroceridae) is 
reported as a new state record for Wisconsin. This is a major range extension, 
because this rarely-encountered species was previously known only from the 
western U.S., specifically Arizona, California, and Nevada. The taxonomic history 
of the species is briefly discussed and hypotheses are offered for its unexpected 
presence in Wisconsin.
 
____________________
Acroceridae, commonly referred to as spider flies, is a fascinating and 
understudied family within the insect order Diptera. Based on personal obser-
vations and correspondence, and as indicated by recent descriptions of species 
and genera (Winterton 2012, Schlinger et al. 2013), the family is also not well-
represented in collections. The life histories of its species are intriguing as well 
in that the larvae are spider parasitoids that exhibit hypermetamorphic develop-
ment (distinctly different larval stages: Schlinger 1987). Based on the examina-
tion of numerous specimen data labels, trapping (especially with Malaise traps) 
appears to be one of the most effective methods of capturing these cryptic flies. 
While examining and identifying acrocerids on loan from the University of 
Wisconsin Insect Research Collection (WIRC) in Madison, WI, two male speci-
mens quickly stood out from the remainder. These specimens were determined 
to be Acrocera bakeri Coquillett, 1904 (Diptera: Acroceridae) (Fig. 1A–D). Not 
only does this discovery constitute a new state record for Wisconsin, it also sug-
gests the range of A. bakeri is considerably wider and much farther east than 
previously known. Prior to this, A. bakeri had been considered a western U.S. 
species, having been recorded only from the western U.S. states of Arizona, 
California, and Nevada (Coquillett in Baker 1904, Sabrosky 1948).  Herein, we 
report this new record, discuss potential reasons for the extension of its range, 
and include figures of the species.
Materials and Methods
Digital images of one specimen were taken in the Song Laboratory of Insect 
Systematics and Evolution at the University of Central Florida (UCF) (recently 
relocated to Texas A&M University) using a Visionary Digital BK Plus Imaging 
System in combination with a Canon EOS 7D camera and 65mm lens (often coupled 
with a 1.4x magnifier) to take multiple images at different focal lengths. The re-
sulting files were converted from RAW to TIFF format using Adobe Lightroom 3.2 
1Song Laboratory of Insect Systematics and Evolution, Department of Entomology, 
Texas A&M University, College Station, TX, U.S.A. (e-mail: asilid@gmail.com).
2University of Central Florida Collection of Arthropods (UCFC), Department of Biology, 
University of Central Florida, Orlando, FL, U.S.A. 
3 Department of Entomology, University of Wisconsin, Madison, WI. U.S.A.
* Corresponding author: (e-mail: dkyoung@wisc.edu).
1
Woller et al.: Comments on a Major Range Extension of the Little-Known Acrocera
Published by ValpoScholar, 2015
2015 THE GREAT LAKES ENTOMOLOGIST 133
Figure 1. Acrocera bakeri male. (A) Habitus, lateral view; (B) Habitus, dorsal view, 
displaying characteristic abdominal pattern; (C) Head, anterior view; (D) Left wing, 
dorsal view. Composite Digital Images: D.A. Woller.
and then stacked into a single composite image using Zerene Stacker (v.1.02). 
Next, Adobe Photoshop CS5 Extended was used to add a scale bar and adjust 
light levels, background coloration, and sharpness.
The habitat image (Fig. 2) was taken using a Canon EOS Rebel T2i digital 
camera and depicts the specific locality where the acrocerids were captured in a 
Malaise trap. This site is dominated by large-toothed aspen, Populus grandidentata 
Michaux, within the confines of Quincy Bluff in southcentral Wisconsin (TNC 
2015). Originally purchased by The Nature Conservancy, Quincy Bluff and 
Wetlands has recently been turned over to the Wisconsin Department of Natural 
Resources for its management. The bluff area is largely managed as an oak-pine 
savanna with smaller prairie restorations, although numerous sites within the 
acreage have significant aspen stands. Malaise traps have been running for sev-
eral years in aspen, mixed oak (Quercus spp.), and jack pine (Pinus banksiana 
Lambert) habitats, but the acrocerids discussed here were recovered solely in 
the aspen or oak-aspen habitat.
The specimens were field collected into 70–80% ethanol. However, since most 
Diptera are prone to excessive tissue distortion during the normal dehydration 
process associated with pinning, the HMDS technique (Nation 1983) was used 
in specimen preparation to minimize exoskeletal collapsing and shriveling.
Two male specimens were examined from the same locality: U.S.A.: WI: 
Adams Co., Quincy Bluff TNC, 43.86627, -089.88363 [WGS84], collected by 
Daniel K. Young, ex: Malaise in Populus grandidentata blow. One specimen was 
collected 13–21 July 2011 and the other 26 July–1 August 2011. Both specimens 
are deposited in the WIRC.
2
The Great Lakes Entomologist, Vol. 48, No. 3 [2015], Art. 5
https://scholar.valpo.edu/tgle/vol48/iss3/5
134 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4
Results and Discussion
The taxonomic history of A. bakeri is convoluted. Prior to Sabrosky (1948), 
males of A. bakeri and Acrocera melanderi Cole, 1919 were comingled with a 
third species: Acrocera bulla auctorum multorum, non Westwood, 1848, which 
was named and described as Acrocera steyskali Sabrosky, 1944 due to his (and 
previous authors’) disagreement with the original description in relation to 
specimens in their possession. Sabrosky (1948) did not indicate specifically 
how A. melanderi and A. steyskali differ, because he wanted to first examine 
the type of A. melanderi. However, he suspected that A. steyskali might be a 
junior synonym of A. melanderi, a suspicion confirmed by Schlinger’s (1965) 
synonymization of the two species. 
Regarding A. bakeri and A. steyskali, Sabrosky (1948) commented that 
males were superficially similar while females were quite different. His couplet 
that separates the two species, his comments regarding the males of A. bakeri, 
and his citing of figures from an earlier work (Sabrosky 1944) indicate that the 
general abdominal color pattern (Fig. 1B) is the primary character separating 
the males of the species. Although Sabrosky (1948) insisted this patterning 
was enough to consider A. bakeri a unique species, it should be noted that he 
possessed only nine specimens, seven of which were males. Furthermore, A. 
bakeri was originally described from a single female from Nevada (Coquillett in 
Baker 1904), while all other known specimens are from Arizona and California 
(Sabrosky 1948). 
We know first-hand that acquiring acrocerid material is generally difficult, 
which, as outlined above, can cause taxonomic issues. Thus, at first, it does seem 
Figure 2. Aspen stand habitat where both male specimens of Acrocera bakeri were 
recovered from a Malaise trap (image taken 29 September 2014).   
Digital Image: D. K. Young.
3
Woller et al.: Comments on a Major Range Extension of the Little-Known Acrocera
Published by ValpoScholar, 2015
2015 THE GREAT LAKES ENTOMOLOGIST 135
remarkable that this hitherto western species has been found in a state so far to 
the northeast, so we offer the following hypotheses to explain this new locality. 
First, it is feasible that the Wisconsin specimens represent a new species 
based largely on the geographic location. We are hesitant to follow this hypothesis, 
because over-splitting in Acroceridae is not unknown, especially in Acrocera and 
Ogcodes (Kehlmaier and Almeida 2014, C.J. Borkent personal communication), 
and we still have very few specimens. C.J. Borkent (personal communication) 
has suggested that a general lack of geographically-intermediate specimens 
has often led to over-splitting, as many species have been described from only 
a few specimens in a small geographic region. Probably, as more specimens are 
acquired, colors, and even patterns, may exhibit variation across the range. 
Recently, Kehlmaier and Almeida (2014) utilized molecular and morphological 
evidence to demonstrate this possibility. They investigated a potential species 
complex in the European acrocerid, Acrocera orbiculus (Fabricius, 1787), and, 
although some degree of differentiation was detected in both sets of evidence, 
they concluded that variation at the genetic level was not significant enough to 
warrant the recognition of multiple species. They posited that a high degree of 
phenotypic plasticity was responsible for the observed differences in specimen 
size and color throughout its range and within populations. 
A second hypothesis (C.J. Borkent, personal communication) is that the 
spiders serving as hosts (currently unknown) for larvae of A. bakeri may have 
moved eastward, whether by human-mediated means or naturally. If it was the 
latter, then it might imply that these spiders move fairly quickly in terms of 
time (1948 until now). Alternatively, the flies, and their spiders, may actually 
have moved westward, and A. bakeri may have simply gone unrecorded in the 
non-western U.S. until now. Yet another possibility is that either the hosts or 
their corresponding flies (or both) are actually widespread across the U.S., but 
the flies are rarely collected. Finally, it is conceivable that these flies and their 
hosts are now becoming more common, in general, due to a suite of ecological 
and environmental reasons, like climatic alteration, human-mediated habitat 
fragmentation, or even host switching. Given the relatively low numbers of ac-
rocerids in U.S. insect collections, none of these ideas are improbable and only 
further collecting efforts will provide support for one to prevail over the others.
Since we possessed only two males, we followed the more conservative 
approach of assigning the Wisconsin specimens to A. bakeri until additional ma-
terial or other evidence indicates otherwise. The Wisconsin specimens strongly 
conform to the pattern concept of Sabrosky (1948), and we see no other obvious 
features to suggest that these males should be considered a new species.
We strongly encourage the continued pursuit of members of this fasci-
nating fly family as increased knowledge will only come from the acquisition 
of more acrocerids; this is not exactly a new idea (Sabrosky 1944), but worth 
repeating. Quite likely, many collections possess undiscovered acrocerid trea-
sures – perhaps contained in the vast unsorted residues of insect traps. Such 
“insect soup” often sits untouched for years in the average collection due to time 
and personnel constraints (ABN 2015). We conclude with this invitation: if you 
encounter unidentified acrocerids and would like them identified (to at least 
the genus level), we encourage you to contact the first author.
Acknowledgments
We are very appreciative to Chris Borkent of the California State Collection 
of Arthropods, California Department of Food and Agriculture for addressing 
the many acrocerid questions we sent his way, for providing us with interest-
ing ideas of his own, and for reviewing an early version of this manuscript. A 
very special thanks to the third author as well for suggesting the loan in the 
first place that led to this intriguing find. We thank Jeff Gruber, an Honorary 
4
The Great Lakes Entomologist, Vol. 48, No. 3 [2015], Art. 5
https://scholar.valpo.edu/tgle/vol48/iss3/5
136 THE GREAT LAKES ENTOMOLOGIST Vol. 48, Nos. 3 - 4
Fellow in the third author’s lab, whose photo of another Acrocera species on-
line (Gruber and UW-Madison Dept. of Entomology 2015) caught the eye of the 
first and second authors and led indirectly to this work. You never quite know 
what tasty morsels will be found within insect soup, so, by all means, dig in! 
Finally, we gratefully acknowledge the constructive input from two reviewers 
of the manuscript.
Literature Cited
(ABN) Australian Bioinformatics Network.  2015.  Insect Soup Challenge! At the 
ICCV 2013 International Workshop on Computer Vision for Accelerated Bioscience. 
Available from http://tinyurl.com/kedtelv (accessed 29 April 2015).  
Coquillett, D. W.  1904.  [Description of Acrocera bakeri], p. 23. In C. F. Baker (ed.), Diptera. 
Reports on Californian and Nevadan Diptera, I.  Invertebrata Pacifica. 1: 17–40.  
Gruber, J., and UW-Madison Dept. of Entomology.  Acrocerid — Acrocera bimacu-
lata — ♀. Available from http://bugguide.net/node/view/220505#311245 (accessed 
29 April 2015).  
Kehlmaier, C., and J. M. Almeida.  2014.  New host records for European Acroceridae 
(Diptera), with discussion of species limits of Acrocera orbiculus (Fabricius) based 
on DNA-barcoding.  Zootaxa 3780: 135–152.  
Nation, J. L.  1983.  A new method using hexamethyldisilazane for preparation of soft 
insect tissues for scanning electron microscopy.  Biotechnic & Histochemistry 58: 
347–351.  
Sabrosky, C. W.  1944.  A revision of the American spider parasites of the genera Ogcodes 
and Acrocera (Diptera, Acroceridae).  American Midland Naturalist 31: 385–413.  
Sabrosky, C. W.  1948.  A further contribution to the classification of the North American 
spider parasites of the family Acroceratidae (Diptera).  American Midland Natural-
ist 39: 382–430.  
Schlinger, E. I.  1965.  Diptera-Acroceridae, pp. 403–407.  In A. Stone, C. W. Sabrosky, W. 
W. Wirth, R. H. Foote, and J. R. Coulson (eds.), A Catalog of the Diptera of America 
North of Mexico.  Agriculture Handbook No. 276.  United States Department of 
Agriculture, Washington, D.C.  1696 pp.  
Schlinger, E. I.  1987.  The biology of Acroceridae (Diptera): true endoparasitoids of 
spiders, pp. 319–327. In W. Nentwig (ed.), Ecophysiology of Spiders.  Springer Verlag, 
Berlin.  529 pp.  
Schlinger, E. I., J. P. Gillung, and C. J. Borkent.  2013.  New spider flies from the 
Neotropical Region (Diptera, Acroceridae) with a key to New World genera.  ZooKeys 
270: 59–93.  
(TNC) The Nature Conservance.  2015.  Wisconsin Quincy Bluffs and Wetlands. 
Available from http://tinyurl.com/qas5ez9 (accessed 29 April 2015).  
Winterton, S. L.  2012.  Review of Australasian spider flies (Diptera, Acroceridae) with 
a revision of Panops Lamarck.  ZooKeys 172: 7–75.  
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Woller et al.: Comments on a Major Range Extension of the Little-Known Acrocera
Published by ValpoScholar, 2015


https://scholar.valpo.edu/cgi/viewcontent.cgi?article=1018&context=tgle

Comments on a Major Range Extension of the Little-Known Acrocera bakeri (Diptera: Acroceridae)

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