Hexatoma (Eriocera) californica (Osten Sacken, 1877)

Podeniene, Virginija & Gelhaus, Jon K., 2015, Review of the last instar larvae and pupae of Hexatoma (Eriocera) and Hexatoma (Hexatoma) (Diptera, Limoniidae, Limnophilinae), Zootaxa 4021 (1), pp. 93-118 : 96-98

Hexatoma (Eriocera) californica (Osten Sacken, 1877)

( Figs. 1–9 )

Diagnosis. Larval and pupal characters as in genus and: larva with maxillary palps 2X as long as mandible; spiracular lobes slender, marginal hair on lateral and ventral spiracular lobes of similar length, lacking extended darker setae on apex of ventral lobes. Ventral spiracular lobes with thin dark median line apically, bifurcating into “Y”-shaped pattern proximally. Mature larva large, about 30 mm long. Pupa with respiratory horns slightly divergent, curved posteriorly, apex narrowed to spine. Cephalic crest with two horns.

Description. Length of last instar larvae— 33–34 mm; width—4.0– 5.5 mm. Body covered with very short yellowish-brown hairs, which gives body golden color. First and anterior part of tenth body segment covered with longer hairs forming longitudinal rows. Posterior part of tenth segment covered with shorter hairs forming long transverse rows. Width of all thoracic and 2nd–8th abdominal segments slightly exceeds length. First abdominal segment very short. Small structures similar to spiracles on tergum of all segments. Last abdominal segment (anal) constricted. Penultimate segment distinctly inflated. Four long stout setae on posterior end of sternite of penultimate segment, equidistant from each other.

Head capsule — 3.1–3.3 mm long, 1.7– 1.5 mm wide. Elongate-oval in shape, depressed dorsoventrally and much reduced, especially ventral side ( Fig. 1 ). Medial labrum border extended and developed, with a lateral, setose, saw-shaped lobe directed outward ( Fig. 2 ). Long and short setae on anterior part of labrum, a prominent tubercle with sensory pegs located behind these setae. Few short sensory structures nearby posterior-lateral side of labrum. Labrum entirely covered with tufts of short setae. Clypeus distinctly divided from labrum. Clypeus diamond-shaped with posterior part tapered into sharp point and anterior part cut off, slightly sclerotized. Frons separated from clypeus, divided into two large rectangular lateral plates. Basal segment of antenna cylindrical with upper part directed outward ( Fig. 3 ), basal segment of antenna long, more than five times as long as wide, with two long and single short setae on the apical part. Apical segment short, sculptured. Mandible sickle-shaped, with a single sharp, curved apical tooth ( Fig. 4 ), three small teeth at the base, first tooth shortest and blunt, second tooth twice as long and sharp, third tooth slightly shorter than second. Inner and outer parts of maxilla fused. Maxilla long and curved outward; apical part covered with dense short hairs. Maxilla twice as long as mandible. Cardo reduced into very small sclerite. Hypopharyngeal part of head capsule membranous. Posterior part of head capsule consists of one pair of rod-shaped internolateralia and one pair of rod-shaped externolateralia. Externolateralia (lateral rods) less sclerotized than internolateralia and almost straight. Internolateralia (dorsal rods) of head capsule straight and diagonal until apical fifth, then medial (inner) margins slightly divergent.

Last segment: Spiracular field surrounded by four flattened elongate lobes ( Fig. 5 ). Dorsal lobe reduced and inconspicuous. Ventral lobe slightly longer than lateral lobe. Lateral lobe almost 2.5 times as long as wide at the base. Ventral lobe almost three times as long as wide at the base. Apical part of ventral lobe with dark brown long hairs, almost as long as lobe. Outer margin of lateral lobe and vestigial dorsal lobe fringed with short hairs. Lateral lobe with narrow, stripe-shaped sclerite on inner margin of lobe, slightly wider at the base. Ventral lobe has very narrow, bifurcate (“Y” shaped), sclerite at base of lobe. Inner branch darker and shorter, outer branch paler, almost reaching spiracles. Spiracles small, circular, widely separated, distance between them more than 5X diameters of a spiracle. Inner circle of spiracle dark brown, outer ring light brown.

Anus surrounded by four long, white, fleshy anal papillae ( Fig. 6 ). Lobes almost cone-shaped, posterior pair slightly longer than anterior pair. Two long setae at the base of each lateral and ventral pair ( Fig. 7 ).

Pupa. Male pupa exuvia about 20 mm long, about 4 mm wide. Head destroyed and details of maxillary palpi and labrum not visible ( Figs. 8–9 ). Cephalic crest prominent, with smooth surface and two horn-shaped lobes ( Figs. 8–9 ). Antennal sheaths of medium length, almost reaching posterior end of wing ( Fig. 8 ). Thorax: length of respiratory horns 1.5 mm, width 0.3 mm, less than half of head width. Respiratory horns wider at base and taper toward the end. Apex of wing sheath almost reaching end of second abdominal segment. Two long setae at base of wing ( Fig. 8 ). Leg sheaths reaching almost two thirds of length of third abdominal segment ( Fig. 8 ). Abdomen: segments II–VII with annuli, dividing each abdominal segment into two parts. Tergite of second abdominal segment with two well developed spines ( Fig. 9 ). Posterior part of tergites and sternites with transverse rows of tubercles with large spines ( Fig. 8 ). Some tubercles (usually marginal tubercles of abdominal segments III–V) with setae instead of spines. Number of spines on dorsum and venter vary, 25–30 spines on tergites of segments III–V; 14–16 tubercles with spines on sternites of segments IV–VI. Tergites of abdominal segment VI–VII have 8 small tubercles with setae instead of spines ( Fig. 9 ). Sternites of third segment with four tubercles with very large spines. Sternite of seventh segment with eight tubercles with spines. Two additional tubercles with two setae located almost in middle of posterior ring (at the level of spiracles). Prominent spiracles almost in middle of pleurites of abdominal segments III–VII. Two (or on some segments three) setae near dorsal margin of spiracle ( Fig. 8 ). A small tubercle with single seta present in middle of anterior part of segments III–VII. Terminal segment of male blunt and narrow. Ventral lobes (anal spines) well developed, long with rounded tips directed dorsally. Tips of anal spines reach posterotergal spines ( Fig. 8 ). Posterotergal spines large, sharp pointed, directed upward. Anterodorsal and mediodorsal spines smaller; similar in shape and size bearing few setae on each tip, situated almost in middle of tergum of terminal segment ( Fig. 9 ). Large tubercle with long seta near anterodorsal spine. Prominent tubercle with two long setae situated on pleurite. Two prominent tubercles with four setae on middle of sternite of terminal segment. Anterior end of terminal segment with 17 prominent tubercles with spines forming ring on the anterior end of terminal segment ( Fig. 8 ).

Specimens examined. 2 last instar larvae and one male pupa exuvia from USA, California Monterey Co., Salmon Creek, 4.IX.1964, collected by C. D. Hynes (UCR collection).

Figures

FIGURES 1 – 5. Hexatoma (Eriocera) californica. 1. General view of head capsule of last instar larva, dorsal aspect. 2. Labrum and clypeus, dorsal aspect. 3. Right mandible, dorsal view. 4. Right antenna, dorsal view. 5. Spiracular field.

FIGURES 6 – 9. Hexatoma (Eriocera) californica. 6. Posterior end of penultimate segment and terminal segment, ventral aspect. 7. Penultimate segment and terminal segment, lateral aspect. 8. General view of male pupal exuvia, lateral aspect. 9. General view of male pupal exuvia, dorsal aspect.