Hymenoptera

Ward, Anna K. G., Busbee, Robert W., Chen, Rachel A., Davis, Charles K., Driscoe, Amanda L., Egan, Scott P., Goldberg, Bailey A. R., Hood, Glen Ray, Jones, Dylan G., Kranz, Adam J., Meadely-Dunphy, Shannon A., Milks, Alyson K., Ott, James R., Prior, Kirsten M., Sheikh, Sofia I., Shzu, Shih-An, Weinersmith, Kelly L., Zhang, Linyi, Zhang, Y. Miles & Forbes, Andrew A., 2022, Borneosa aspera, Zoological Studies 61 (57), pp. 1-30 : 18-21

( Hymenoptera : Chalcidoidea: Eulophidae : Entiinae )

816 individuals (mean = 81.6, range 1–402) reared from 10 gall types ( Table S1).

Summary of Natural History: Euderus is a moderately large genus, with> 75 species described worldwide. Where hosts are known, they are usually pupae in concealed habitats (e.g., leaf mines, inside fruits and stems) ( Yoshimoto 1971). More rarely, Euderus attack insects in galls, with two oak gall associated species— Euderus crawfordi Peck and Euderus set Egan, Weinersmith & Forbes-known from the Nearctic ( Yoshimoto 1971; Egan et al. 2017). Euderus set has been specifically studied as a behavioral manipulator of its host gall wasps-wasps with E. set infections chew significantly smaller exit holes in their galls than those that are not infected and then do not leave the gall but instead plug the exit hole with their head. Euderus set then consumes the body of the host wasp and leaves the gall by chewing a hole through its host’s head ( Weinersmith et al. 2017; Ward et al. 2019). Though this behavior has only been studied in detail for E. set , evidence of “head plugs” has been found in museum collections of Southwestern U.S. Bassettia Ashmead galls ( Egan et al. 2017).

Relationship to galler phylogeny: We reared or found records of Euderus in association with nine gall types in the Nearctic gall wasp phylogeny ( Ward et al. 2022). Seven of these (indicated by “s” in Fig. 8a ) have been previously identified as E. set ( Ward et al. 2019) . Euderus crawfordi (“c” in Fig. 8a ) has been reared from the Palearctic species Plagiotrochus suberi Weld , but only from galls in its introduced range in the Nearctic suggesting this is a derived host association. Euderus crawfordi is also known from the Nearctic Kokkocynips coxii (Bassett) , which is not on the Ward et al. (2022) tree, but we have indicated its approximate location near its congener, Kokkocynips imbricariae (Ashmead) (“c” with two asterisks). Our collections also produced what appears to be a new species of Euderus associated with galls of the sexual generation of Neuroterus washingtonensis on the Pacific coast (“n” in Fig. Xa). The morphology of these wasps did not match that of E. set , nor any species described in Yoshimoto (1971). Two other Euderus reared from galls in the southwestern U.S. were not examined morphologically and their hosts were not among those on the Ward et al. (2022) tree.

Biogeography and oak tree section: Euderus set was reared from seven gall types, all in Eastern North America but across all three oak sections ( Fig. 8b c ). Euderus were reared from two types of gall in the Mexican and Central American floristic region (both on section Quercus oaks), and from one gall type in the Californian floristic province (also section Quercus ).

Tree organ and gall size: Gall hosts were only on stems, leaves, or petioles ( Fig. 8d ). Euderus attacked a greater proportion of large (> 2 cm) galls (0.26) than medium galls (0.06), and no Euderus were reared from galls smaller than 5 mm ( Fig. 8e ).

Co-occurrence with other natural enemies: Euderus were found to occur alongside Ceroptres (P = 0.015) and Euceroptres (P = 0.001) significantly more often than expected ( Fig. 8f ). This co-occurrence is unlikely to be because Euderus are using wasps in either of these two genera as their primary hosts - the particular biology of Euderus set causes the host to be visible from outside of the gall and the gall inducer has been shown to be the host in cases where this has been investigated ( Weinersmith et al. 2017; Ward et al. 2019). Other hypotheses for the significant co-occurrence are that wasps in these three genera tend to attack galls with similar features, and/or that they all tend to attack galls in a similar temporal window ( Ward et al. 2019).

Additional Notes: Because we are primarily working at the level of genus or above and patterns of specialization are more likely to manifest at the species level we have not sought to test hypotheses about insect specialization on gall morphology in this paper. However, since we have Euderus rearing records to the level of species, here we can compare features of their associated galls. Previous work has noted that Euderus set has only been reared from integral galls that lack external defensive structures, perhaps because Euderus appear to attack late-stage pupae and have relatively short ovipositors ( Ward et al. 2019). This pattern of host use-medium to large, integral (non-detachable) swellings, often with> 1 cells-appears to apply to E. crawfordi and to the putative new Euderus species reared from Neuroterus washingtonensis as well ( Fig. 8a ; Table S1).

Other Common Affiliates - Superfamily and Family level IDs

Eulophidae ( Hymenoptera : Chalcidoidea: Eulophidae )

We reared 21,232 (mean = 259, range = 1–8,655) eulophid wasps from 82 gall types. These counts exclude wasps in subfamily Entiinae ( Euderus ), which were treated separately above. Previously documented Eulophid associates of oak galls include representatives of the Entedoninae (Chrysochari s Förster, Eprhopalotus Girault , Horismenus Walker , Pediobius Walker ), Eulophinae ( Aulogymnus Förster , Cirrospilus Westwood , Pnigalio Schrank , Sympiesis Förster ), and Tetrastichinae ( Aprostocetus Westwood , Baryscapus Förster , Galeopsomyia Girault , Minotetrastichus Kostjukov , Pentastichus Ashmead , Quadrastichus Gilrault , Tetrastichus Walker ) ( Askew et al. 2013; Noyes 2022).

Relatively little is known about the ecology of eulophid gall associates, including their trophic roles, host ranges, and details of their life cycles. Representatives of many eulophid genera and subfamilies are known as obligatory or facultative hyperparasitoids ( Schauff et al. 1997), and eulophid larvae in some oak galls can be gregarious (Redfern and a) b)

1

c*

2

3

s

4s

7865

1210119

sn

13

14

15

16

17

18

19

20

21

22

23

24

s

25

26

29

28

27

c)

303132343335 c**

Q 5 77

36

37394038

L 3 27

41

424443454647

s

V

48

49 s 50 s

5351

52

d)

54575655

3 2

5958

(66) (26)

60

61

62

63666465670 0

6869

(12) (4)

70

71

72

73

7478757776

4 0

8079

(10) (4)

81

82

83

e) f)

g)

Askew 1998). Several different eulophid species have previously been reared from the same gall type (e.g., Askew 1961; Eliason and Potter 2000; Bird et al. 2013), but they may or may not be attacking the same host(s) in these communities. Future integrative taxonomic work that includes host relationships will be invaluable in understanding this important group of gall associates.

Eupelmidae ( Hymenoptera : Chalcidoidea: Eupelmidae )

We reared 10,620 (mean = 190; range = 1–3,802) eupelmid wasps from 56 gall types ( Table S1). The Eupelmidae most commonly associated with oak galls are genera Brasema or Eupelmus Dalman , and it is likely that all or most of our collections are from one of these genera (though we note that Anastatus gemmaii (Ashmead) was originally recorded from Callirhytis quercusgemmaria Ashmead ( Burks 1967)) . Many Brasema have been mistakenly classified as Eupelmus , and sexual dimorphism in the family makes it challenging to separate males ( Gibson 2011), such that we felt it was premature to split the two genera here.

Brasema and Eupelmus are both ectoparasitic on insect larvae or pupae, and many previous Holarctic oak gall associations have been recorded ( Noyes 2022). Associations with Palearctic oak gallers are known to involve direct parasitism of oak gall wasps, as well as parasitism of their Synergus inquilines ( Redfern and Askew 1998). We have at least two records of Brasema emerging from the same monothalamous leaf gall as an adult Belonocnema kinseyi Weld oak gall wasp ( Hall 2001), strongly suggesting that at least some of our collections represent indirect associations with the galler.

Ichneumonoidea ( Hymenoptera )

We reared a combined 229 (mean = 11.5, range = 1–80) ichneumonid and braconid wasps from 20 gall types. All but one of the ichneumonoid collections were reared from medium-sized galls or larger (> 0.5 cm) on stems, leaves, or petioles ( Table S1). Though we did not key all of these wasps to genus, the majority of these collections were wasps in the genus Allohorgas ( Braconidae : Doryctinae ). Allohorgas has previously been reared from several North American galls ( Eliason and Potter 2000; Forbes et al. 2016; Weinersmith et al. 2020; Joele et al. 2021). Braconid wasps from subfamily Cheloninae were reared from Disholcaspis quercusmamma (Walsh & Riley) and Callirhytis frequens (Gillette) galls. Ichneumonidae were reared from Neuroterus washingtonensis , Disholcaspis quercusglobulus (Fitch) , Disholcaspis quercusmamma , and Neuroterus saltaorius (Edwards) .

The ecology of the oak gall-associated wasps in superfamily Ichneumonoidea is still generally unknown. Recent work on genus Allorhogas shows it to be particularly labile with respect to its feeding habits, with some species acting as parasites, others as phytophagous inquilines, still others as seed predators, and some as gall formers themselves ( Moreira et al. 2017; Samacá-Sáenz et al. 2020 2022). In oak galls, Allorhogas and other ichneumonid wasps may be attacking moth or beetle inquilines: Joseph et al. (2011) reported Bassus nucicola Musebeck ( Braconidae ) and an unidentified ichneumonid wasp, both thought to be parasitizing Cydia latiferreana Walsingham in galls of Andricus quercuscalifornicus . Cheloninae are also primarily known as parasitoids of Lepidoptera ( Wharton et al. 1997) .

Pteromalidae ( Hymenoptera : Chalcidoidea: Pteromalidae )

We reared 7,545 (mean = 148; range = 1–2,385) pteromalid wasps from 51 different gall types ( Table S1). Our pteromalid collections were reared from galls in all three floristic regions and from all three oak tree sections. Existing keys, which acknowledge their own difficulty and incompleteness (e.g., Bouček and Heydon 1997), were insufficient for separating many of these wasps to the genus level within this large and polyphyletic family, so they will be addressed elsewhere in the future through integrative taxonomic approaches. The Western Palearctic fauna of oak gall-associated Pteromalidae includes at least nine genera ( Arthrolytus Thomson , Cecidostiba Thomson , Caenacis Förster , Cyrtoptyx Delucchi , Elatoides Nikol'skaya, Hobbya Delucchi , Kaleva Graham , Mesopolobus Westwood , and Ormocerus Walker ) ( Noyes 2022). At least three of these ( Arthrolytus, Cecidiostiba , and Ormocerus ) are also known from Nearctic oak galls. Additional Nearctic gall-associated pteromalids include Acaenacis Girault , Amphidocius Dzhanokmen , Anisopteromalus Ruschka , Guolina Heydon , Lariophagus Crawford , and Pteromalus Swederus.

Where the ecology of oak gall-associated pteromalids has been studied, they are ectoparasites of a variety of gall inhabitants. Some attack the gall wasp itself, while others parasitize inquilines or other parasitoids ( Askew 1961). Mesopolobus are the best studied of the Palearctic oak gall-associated pteromalids and feed on several different gall inhabitants, and at various life stages, including adults ( Askew 1961). As many as five different species from this genus have been reared from the same gall type ( Redfern and Askew 1998). Experiments on host searching suggest that short range searches for galls by Mesopolobus wasps may rely more on visual cues than on olfaction ( Askew 1961), such that host tree and/or gall morphology may be axes of specialization to explore for these and other pteromalids.

Occasional associates ( Hymenoptera )

Bethylidae ( Hymenoptera : Chrysidoidea: Bethylidae )

We reared 37 (mean = 5, range 1–16) bethylid wasps from seven gall types. A previous study found a wasp in bethylid genus Goniozus Förster in a gall of Belonocnema fossoria Weld ( Forbes et al. 2016) , and other Goniozus have been reared from moth inquilines in oak galls ( Fouts 1942). The four gall types with the most bethylid wasps in our collections ( Andricus quercuspetiolicola and three species of Belonocnema ) also produced moths, indicating a possible trophic connection.

Figures

Fig. 8. Summary of data for Euderus collected from Nearctic galls. For full explanation of figure details, refer to figure 1 legend. a) Associations of Euderus with the Nearctic oak gall wasp phylogeny (Fig. S1). “s” = Euderus set, “c” = Euderus crawfordi, “n” = possible new Euderus species. * = this association with a Palearctic oak tree is only known from trees introduced to California. ** = the approximate phylogenetic location of this host of E. crawfordi (see text). b) Gall types from which Euderus were reared in the Californian (blue), Mexican and Central American (orange), and Eastern North American (green) floristic provinces. c) Associations of Euderus with trees in sections Quercus (Q), Lobatae (L), and Virentes (V). d) Association of Euderus with gall types on different oak tissues. e) proportion of gall types of three size categories (“small” <0.5 mm; “medium”, “large”> 20 mm) from which Euderus were reared. f) Results of probabilistic co-occurrence analysis for Euderus against seven other common associates. Yellow = significantly less likely to co-occur; blue = significantly more likely to co-occur; gray = no difference from probabilistic expectations. g) Euderus lateral habitus.