Grylloblatta sp.

Herhold, Hollister W, Davis, Steven R, Degrey, Samuel P & Grimaldi, David A, 2023, COMPARATIVE ANATOMY OF THE INSECT TRACHEAL SYSTEM PART 1: INTRODUCTION, APTERYGOTES, PALEOPTERA, POLYNEOPTERA, Bulletin of the American Museum of Natural History 459 (1), pp. 1-184 : 1-184

Grylloblatta sp.

“Ice crawler”

Figures 72 (lateral), 73 (dorsal, ventral)

Plates 45 (lateral), 46 (dorsal, ventral)

Ice crawlers are remarkably active insects given their ecology, and studies have investigated their tolerance to cold ( Schoville et al., 2015). Grylloblatta head morphology, especially musculature, was detailed by Wipfler et al. (2011) using both micro-CT and scanning electron microscopy, but tracheal morphology was notably absent from this study. As the sister group to Embioptera and Phasmatodea , the tracheal morphology of Grylloblattodea was important for assessing homology of these orders.

Several head tracheae, including H-Oc, are difficult to localize. Grylloblattodea have very few ommatidia ( Wipfler et al., 2011), and perhaps this is why tracheation appears reduced around the eyes relative to other taxa. In the thorax, T2-DB branches off T2-L, an unusual condition, as typically T2-DB extends directly from T2-S. This branch is very likely T2-DB, as it leads to T2-DLT, T3-DLT, and successive tracheae as seen elsewhere. The branching pattern of T2,3- AWL and PWL is also notable, in that it is unclear if these tracheae branch from T2,3-DB or directly from T2,3-S. Both conditions are present in other taxa, and this could merely be an “intermediate” positioning.

DESCRIPTION: HEAD: Major tracheae indicated in plates, refer to figure 74 for head detail. Due to looping, networked 3-dimensional nature of Grylloblatta head tracheae, readers are encouraged to refer to digital supplemental models (see Availability of Digital Data, above). H-DCT slightly ventrad at cervix, curving dorsally on entry into head capsule; H-DCT divides into H-DCT-Vi1, H-DCT-Vi2, and H-Ant anteriad of cervix. H-DCT-V1 lateral and anteriad, following head capsule wall. H-Ant anteriad, curving laterally to extend into antennae. H-DCT-Vi2 anteriad, with each side curving anteriad to meet in X-shaped intersection at H-DX and continuing anteriorly before arcing ventrad to connect with H-VCT-Loop via dorsal-ventral branch H-DVB. H-Ant on specimen left side with link to H-DVB. Just posteriad of cervix, each H-DCT with small branch extending medially, joining in Y at base of head capsule into medial branch, extending anteriad as H-DCMedB (dorsal cephalic medial branch). H-DCMedB splits near vertex into three branches; two extend laterally, looping backward to connect with H-Ant as H-DCT-Loop; last branch directly dorsad, connecting to H-DX. H-VCT directly anteriad, with H-Lbm branching ventrad at posterior margin of submentum. H-VCT continuing anteriad with branches to H-Md and H-Lbr before curving medially to join H-VCT from opposite side in dorsal two branches of X-shaped H-AX. Ventral two branches of H-AX formed by H-Lbm, which continues anteriad before arcing dorsally to H-AX, forming H-Lbm-Loop. H-LbmPlp branching from H-Lbm-Loop near anterior curve of H-Lbm toward H-AX. H-Lbm extending anteriad from H-AX anteriormost point; H-Md extending anteriad from dorsal portion of H-Lbm-Loop before curving ventrad. H-DVB dorsal-ventral connection of H-DCT and H-VCT at branching off point of H-Md. Small H-VC running ventrad near anterior end of H-VCT-Loop.

THORAX: T2-S with four branches: H-DCT, H-VCT, T2-DB, T2-VB. T2-CT absent. H-DCT runs anteriad from T2-S with slight curve medially; branching of T1-PL and T1-Dvi at posterior margin of prothorax, with T1-PL running laterally and ventrad, proceeding into proleg and T1-Dvi directly anteriad; T1-DB beginning just anterior of this split, extending dorsad to join with T1-DLT in Y-shaped junction. H-DCT compressed laterally anterior of the split; compression likely preservational artifact. H-VCT similar in size to H-DCT, with single T1-L branching directly ventrad, located mid prothorax. T2-DB running initially dorsad splitting off large T2-AWL, smaller T2-DB continues, extending medially and dorsad, arcing posteriorly to connect to T3-S via T2-DLT. T2-AWL arcing ventrally and posteriad, dividing into T2-AL and T2-Awba; T2-AL continuing posteriorly into midleg, joining with T2-PL near mesothoracic coxa; small T2-Awba branching from T2-AWL, dorsad near apex of arc toward T2-L. T2-VB short, proceeding ventrad and medially before splitting into T1-VLT anteriad and T2-VLT posteriad and ventrad. T1-VLT with three ventral commissures: T1-VC1 most anterior, at the apex of a long oval loop reaching the posterior end of the cervix; T2-VC2 ventrad, joining at the opposite end of loop to forming X-shaped T1-VX; T2-VC3 near the prothoracic coxae; T1-AL-VC branching ventrad from T1-AL to connect with loop at halfway between T1-VC1 and T1-VC2. T2-VLT runs ventrad and posteriad, extending toward mesothoracic coxae before turning dorsally to join with T3-VB. T2-VLT with three ventral commissures: T2-VC1 most anterior, branching directly toward midline to join with opposite side; T2-VC2 branching inward where T2-VLT arcs dorsally; T2-VC3, branching from metathoracic portion of T2-VLT, branching medially and joining with T2-VC2 at X-shaped intersection T2-VX. T2-Cx comprised of two branches, one each extending from T2-VC2 and T2-VC3. T3-S with only two branches, short T3-DB and T3-VB. T3-DB dorsad, splitting into T2-PWL anteriad and ventrad, T3-AWL arcing dorsad and posteriorly, and remaining small T3-DB continuing dorsally to link T2-DLT and T3-DLT in Y-shaped junction. T3-AWba absent; T3-AWbr absent. Short T2-PWL runs anteriad, dividing into ventral T2-PL that links with T2-AL from anterior, continuning into T2-L; and small dorsal T2-PWba. T2-PWbr not present. T3-VB short, bifurcating into connection to T2-VLT from anterior and continuing as T3-VLT toward posterior. T3-VLT with two ventral commissures: T3-VC1 slightly ventrad from T2-VLT/ T3-VLT intersection; T3-VC2 where T3-Cx extends into base of metacoxae. T3-VLT extends from split of T3-Cx, continuing in shallow, ventral arc to link with A1-VLT via A1-VB.

ABDOMEN: A1..8-S present. All abdominal segments similar, with notable exceptions below. Short A n -SB present, bifurcating into A n -DB and A n -VB. A n -DB runs directly dorsad, linking with A n -DLT in Y-shaped junction; A5-DB with short A5-DB-Vi extending mediad. A n -DLT runs in shallow, dorsal arch along tergum; A n -DC absent; short, mediad A4..6-DLT-Vi present; A7-DLT-Vi beginning posteriad before arcing medially and then anteriad, extending past A6-S; A8-DLT extending posteriad into A-Cr. A1-SB with two tracheae ventrad: T3-L ventrad and slightly anteriad, extending into hind leg, along same path as A1-SB; A1-VB smaller, extending directly ventrad. A[2,4]-VB extending directly from A[2,4]-SB with no branches. A3-VB runs directly from A3-SB, with A3-VB-Vi continuing ventrad before turning posteriorly while smaller A3-VB directly ventrad. A[5,6] similar to A3 with large A[5,6]-VB- Vi anteriad and smaller A[5,6]-VB ventrad. All A n -VB-Vi link with A n -VLT in Y-shaped junction, similar to A n -DLT, but with a less pronounced arch ventrad. A8-VC present, other ventral commisures not visible and likely absent. Small A9-VC visible.

Figures

FIGURE 72. Grylloblatta sp. (Gryloblattodea: Grylloblattidae) lateral.

FIGURE 73. Grylloblatta sp. (Gryloblattodea: Grylloblattidae) dorsal (left) and ventral (right).

FIGURE 74. Grylloblatta head trachea detail in A. dorsal, B. ventral, and C. lateral views. Head is not in same orientation as plates and has been rotated to visualize smaller tracheae more easily.