THE LARVA OF IIELIOCAUSUS LARROIDES 
(HYMENOPTERA, SPHECIDAE) 
By Howard E. Evans 
Museum of Comparative Zoology 
Heliocausus is one of several interesting genera of sphecid wasps 
wdiich has been known only from the adult stage. I therefore wel- 
come the opportunity to describe larvae of H. larroides (Spinola) 
sent to me recently by Manfredo A. Fritz of Buenos Aires, Argen- 
tina. My description is based on four fully grown larvae from El 
Salto, Valparaiso, Chile, collected by Dr. Fritz on 24 December 
1969. I shall defer a discussion of larval characters until after the 
description. 
Body . — -Length 9 mm; maximum width 2.8 mm. Fusiform, 
somewhat curved anteriorly ; pleural lobes moderately prominent ; 
terga indistinctly divided into two annulets each ; apical abdominal 
segment rather slender and protuberant, the anus terminal (Fig. 2). 
Spiracles weakly pigmented, inconspicuous; atrium lined with weak, 
irregular polygons; opening into subatrium unarmed; subatrium 
abruptly widened and much folded just beneath atrium (Fig. 6). 
Integument mainly smooth and without setae or spinules, but ex- 
treme anterior part of prothorax, the “neck” region, densely spinulose, 
also thoracic venter somewhat spinulose and dorsum with sparse, 
minute setae, the largest about 20 /i long. 
Head. — Subcircular, width .75 mm; height (exclusive of labrum) 
about the same; front of head with a pair of longitudinal, welt-like 
elevations just mesad of the antennae; coronal suture and parietal 
bands weakly developed ; front surface of head weakly pigmented, 
light brown (Fig. 1). Antennal orbits circular, about 85 /x in 
diameter, antennal papillae barely longer than thick, 25 [i long 
(Fig. 7). Head very sparsely punctate, some of the punctures near 
the vertex, on the lower sides, and on the clypeus bearing short 
setae. 
Mouthparts. — Labrum with about 24 strong setae as well as a 
subapical row of 16-18 small sensilla; apical margin spinulose, 
especially laterally; epipharynx mainly papillose, but the papillae 
grading into spinules medio-basally and laterally, also with a. few 
small sensilla (Fig. 3). Mandibles approximately twice as long as 
their maximum width, with a single rounded tooth on the inner 
margin in addition to the apical tooth ; base with a single lateral 
sensillum (Fig. 5). Maxillae densely spinulose along the mesal 
