Chrysops beameri Brennan, 1935

Goodwin, James. T., 2013, Immature stages of some eastern Nearctic Tabanidae (Diptera). IX. Chrysops beameri Brennan and Hybomitra trispila (Wiedemann), Insecta Mundi 2013 (318), pp. 1-5 : 1-3

Chrysops beameri Brennan

Mature larva ( Fig. 1 ). Body pale yellowish; 12-14 mm long; with stigmatal spine. Head capsule length 1.4 + 0.05 mm; greatest width about 0.36 mm. Larval exuvium with area on each abdominal segment anterior to ring of pseudopodia with a semi-opaque, faint brownish cast that contrasts rather noticeably with adjacent areas of transparent colorless integument. Striations present on all non-pubescent aspects of body other than above-mentioned areas anterior to pseudopodia on abdominal segments, except on segments 9-10 where a few striae are visible immediately in front of lateral pseudopodia; striae more widely spaced dorsally and ventrally on segments than laterally and more widely spaced on meso- and meta-thorax than corresponding aspects of abdominal segments. Pubescence pale, more readily visible on anal segment. Anterior pubescence encircling segments 1-8, absent laterally on segment 9, and restricted to dorsal or dorsolateral, ventrolateral, and midventral patch on segment 10; prothoracic annulus broad, covering about one-half of segment laterally; meso- and meta-thoracic annuli without caudal projections, covering about 1/3 and 1/4 of segments; laterally; annuli on segments 4-8 relatively wide with the only narrow clear areas between them and pseudopodia. Posterior pubescence encircling anal and preanal segments and restricted to lateral margins on segment 9; posterior annulus of preanal segment with blunt anterior projection laterally, annulus on anal segment covering between one-half and two-thirds of segment dorsally and broadly joining pubescence of anal ridges ventrally, its anterior margin with a configuration as in Fig. 1 , the semi-detached patch shown laterally may be fully detached from, or more broadly joined to, posterior annulus in other specimens. Anal segment with additional pairs of small circular patches of pubescence near anterior margin dorsally and laterally.

Pupa ( Fig. 2 A-2B). Body 9.5-10.5 mm long. Color uniformly pale yellowish brown although mid-vertex and anterior dorsal thoracic spot often faintly darker. Antennal ridges sharply crested, each partially or almost entirely divided sublaterally; median portion elevated 0.08-0.09 mm above median cleft, usually skewed medially; outer portion less than half height of median portion. Callus tubercles elevated approximately 0.05 mm, strongly shriveled in appearance. Antennal sheaths slightly surpassing epicranial suture. Prominent grooves extending from upper basal angle of antennal sheaths to callus tubercles. Vertical and orbital setae on small tubercles. Thoracic spiracles 0.32-0.35 mm long, usually more abruptly bent near posterior third; mounted on spiracular prominences that extend anteriorly beyond dorsal margin of thorax up to 0.1 mm. Prealar setae paired. Spinous fringes present on all aspects of abdominal segments 2-7; all spines attenuate. Fringe of tergum 7 with 21-28 spines.

Collections. All larvae of C. beameri were found at the same location in the wetlands on the northeastern corner of Jarvis Christian College, Hawkins, Wood County, Texas (32.5904444, -95.1738888). The single collecting site is a wet area adjacent to a small stream created by the outfall from a metal culvert passing under the dam encircling a small manmade stock pond. This pond receives, in addition of precipitation and surface runoff, a continuous input of 45-60 liters per minute from the ‘artesian’ flow of an abandoned well. This constant input from the abandoned well causes the pond to overflow through the culvert, even in most dry periods, into the area where the larvae were collected. Due to ‘artesian’ inflow, the pond water and the water below the culvert are generally several degrees cooler than both standing and flowing water in other nearby standing and flowing water. The area where the larvae were found is a combination of wet, silty, highly organic ‘muck’ around the roots of aquatic vegetation (water pennywort, Hydrocotyle spp .). The area of collection remains wet year round, although the rate of flow varies depending on amount of recent rainfall. Other species of Tabanidae found in association included Merycomyia whitneyi (Johnson) , Chrysops celatus Pechuman , C. cincticornis Walker , C. upsilon Philip , C. vittatus Wiedemann , Tabanus nigrescens Palisot , T. petiolatus Hine , T. pumilus Macquart , and T. trimaculatus Palisot.

Comments. In the key to larvae of Chrysops Meigen presented by Teskey, (1969), larvae of C. beameri key to the first choice in couplet 3. In Teskey’s key the first choice leads to couplet 4 which separates C.

niger Macquart and C. calvus Pechuman and Teskey. Below couplets 3 and 4 of Teskey’s key, less his references to figures, are modified to include C. beameri by inserting a new couplet 4.

3.

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Anterior pubescent annuli on pro- and meso- thorax wide, covering approximately 1/2 and 1/3 length of segments, respectively. All thoracic annuli lack posterior pubescent projections .... 4

Anterior pubescent annuli on thoracic segments narrower and with .......... posterior pubescent projections laterally .................................................................................................................... 6

4(3).

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Pubescence present and relatively distinct on anterior of first seven abdominal segments and also encircling anterior of anal segment ........................................................ C. beameri Brennan

If pubescence is present on first seven abdominal segments, it is very pale, and anal segment lacks anterior pubescence .......................................................................................................... 5

5(4).

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Pubescence present, though very pale, on anterior of first seven abdominal segments ...............

..................................................................................................................... C. niger Macquart Pubescence absent from first seven abdominal segments .... C. calvus Pechuman and Teskey

Pupae of C. beameri would key to C. macquarti Philip in couplet 16 of Teskey’s key to pupae of Chrysops . If a new couplet was added to Teskey’s key, because the pupae of the two species are so similar, the only point of separation found was that the callus tubercles of C. beameri are elevated 0.05 mm or less and those of C. macquarti are elevated about 0.08 mm.

The specimens on which the above descriptions are based are deposited in the Florida State Collection of Arthropods, Gainesville, FL.

Figures

Figures 1-2. Chrysops beameri. 1) Illustration of the pubescence pattern of in lateral view. 2). Images of the pupa: A. ventral view of frontal plate; B. dorsal view of posterior segments of abdomen.