Great Basin Naturalist

Volume 35 Number 1 Article 16

3-31-1975

The nest and larva of Diploplectron brunneipes (Cresson) (: )

Howard E. Evans Colorado State University, Fort Collins

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Recommended Citation Evans, Howard E. (1975) "The nest and larva of Diploplectron brunneipes (Cresson) (Hymenoptera: Sphecidae)," Great Basin Naturalist: Vol. 35 : No. 1 , Article 16. Available at: https://scholarsarchive.byu.edu/gbn/vol35/iss1/16

This Article is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. THE NEST AND LARVA OF DIPLOPLECTRON BRUNNEIPES (CRESSON) (HYMENOPTERA: SPHECIDAE)

Howard E. Evans^

Abstract.— Diploplectron brunneipes (Cresson) makes a shallow nest in compact clay-sand con- taining at least two cells. It is provisioned with immature Heteroptera. The larva resembles that of in a general way but differs in several particulars.

Wasps of the genus Diploplectron es- the entrance. Each cell contained 6 im-

( ape frequent detection because of their mature bugs, Uhleriola floralis (Uhler) small size (4-7 mm) and secretive behav- (Lygaeidae) [det. J. A. Slater] and a ior. For many years the genus was poorly small larva, one of which was reared to understood, but in 1972 there appeared maturity and is described below. Both of two important papers: Parker presented these cells had been closed off with a bar- a revision of the 15 New World species, rier of sand. Since the had just with notes on the biology of 4 of them; brought in prey, there must have been a and Kurczewski published a fairly detailed cell in the course of being provisioned (or study of the nesting behavior of one prey stored in the burrow), but this was of these (D. peglowi Krombein). The not found. 1 he cells were broadly ellipti- present paper includes brief observations cal, measuring about 3x4 mm. The bugs, on a previously unstudied species, D. brun- all approximately the same instar, were neipes (Cresson), as well as the first de- in some cases on their backs, in other scription of a larva of this genus. The cases on their sides. latter is of some importance, as knowledge Description of Larva of the larvae of this subfamily (Astatinae) Length (measured in usual curved posi- has previously been based only on the tion) 6.2 mm; maximum width 2.3 mm; genus Astata, and there are some dis- maximum height (4th abdominal seg- crepancies in the published information ment) 2.4 mm. Body fusiform, middle seg- on that genus. ments somewhat himiped dorsally, 4th These observations were made along abdominal segment more humped than the shores of Terry Lake, just north of the any other; anus terminal and supraanal city of Fort Collins, Colorado. D. brun- and subanal lobes equally developed (Fig. neipes was not uncommon during July 2). Pleural lobes rather weakly devel- and August 1974, especially in strips of oped; division of segments into dorsal an- bare, flat soil on top of a bank bordering nulets indistinct posterior to middle of the beach proper. A number of females body. Integument smooth and glistening, were seen walking and flying about low under high power seen to have a very few vegetation, apparently hunting. Only one minute setae, chiefly on the dorsum and nest was found. This was located in the pleural lobes of the more anterior seg- center of a bare strip of rather hard- ments, also sparse, minute spinules on packed sandy clay. On 24 July a female parts of the venter and pleura. First pair was seen walking in a circuitous path of spiracles slightly larger than the others; holding a small bug in her mandibles. atrium somewhat pear shaped, sparsely After a few moments she plunged into a lined with anastomosing ridges; peritreme small, open hole having a diameter of 2.5 distinct; opening into subatrium simple, mm and having no evidence of a mound unarmed (Fig. 5). of soil around it. Head 0.9 mm wide, 0.7 mm high (ex- The female was captured when she clusive of labrum) (Fig. 1). Head largely emerged from this hole a few minutes unpigmented, except mandibles and pleu- later. The burrow was found to penetrate rostomal thickenings brownish; center of the soil at about a 60 degree angle with front with paired, small depressions; pari- the surface. Two cells were located, at etal bands very weak. Antennal orbits el- depths of 5.5 and 6.5 cm, the two cells liptical, papillae only slightly longer than being 4 cm apart and about 9 cm from wide at base. Head with only a very few

^Department of Zoology and Entomology, Colorado State University, Fort Collins, Colorado 80523. Part of a study of the comparative behavior of solitary , supported by the National Science Foundation, grant GB-43790.

123 124 GREAT BASIN NATURALIST Vol. 35, No. 1

Figs. 1-5. Diploplectron brunneipes, mature dible, ventral (posterior) aspect; 5, anterior tho- larva: 1, head; 2, body, lateral view; 3, labrumracic spiracle, high magnification, (left side) and epipharynx (right side); 4, man- small setae. Labrum 0.33 mm wide, with a lae short, directed mesad, inner surface strong V-shaped median emargination; roughened but not distinctly spinulose; surface with about 20 small setae, also galeae very much more slender than ])al- with a fe w^ small marginal sensilla, pi. Hypopharynx inconspicuous and evi- mainly laterally; epipharynx with 6 dently not spinulose. I^abium without se- strong sensillae surrounding the emargin- tae or spinules, spinnerets blunt, consider- ation and some weaker ones basal of these, ably exceeding the palpi. otherwise clothed with very fine spinules except medially (Fig. 3). Mandibles stout, Discussion with 5 strong teeth, one of them ventral of the most apical tooth (Fig. 4); upper The nest of D. hrumieipes closely re- surface with a single minute seta. Maxil- sembles that of D. peglowi Krombein, as March 1975 EVANS: WASP NEST AND LARVA 125 described by Parker (1972) and Kurczew- laid on the ventral side of a bug placed ski (1972), although evidently in flatter with its dorsum upward in the bottom of and more compact soil than that species the cell (Evans, 1957). I had assumed usually occupies. The angle of the bur- that the humped 4th abdominal segment row, depth and size of the cells, and open represented a pseudopod that assisted the nest entrance are similar in the two spe- larva in feeding in this unusual position. cies, as are the type of prey and manner However, the species of Diploplectron of prey carriage. place the bugs in the cell in various posi-

The larva is basically similar in struc- tions, and according to Kurczewski (1972) ture to that of Astata as described by the bug bearing the egg is found either Evans (1958), although differing in some on its side or with its venter upward. Of details from descriptions provided by earli- course the middorsal hump may still serve er workers. The paired spinnerets, to assist the larva in pushing itself about humped fourth abdominal segment, ter- from prey to prey, though it seems less minal anus, short antennal papillae, stout suitably adapted for this type of feeding. mandibles, mesally directed maxillae, and smooth integimient together clearly Literature Cited define the Astatinae as distinct from other Evans, H. E. 1957. Ethological studies on dig- subfamilies. One other feature that I ger wasps of the genus Astata (Hymenop- used to define the subfamily, the pres- tera, Sphecidae). J. N. Y. Ent. Soc. 65:159- ence of numerous setae on the mandibles, 185. . 1958. Studies on the larvae of digger does not hold up, and it represents an im- wasps (Hymenoptera, Sphecidae). Part IV: portant difference between the larvae of Astatinae, Larrinae. and Pemphredoninae. Astata and Diploplectron. Other differ- Trans. Ainer. Ent. Soc. 84:109-139. ences include the 5-toothed mandibles of Kurczewski, F. E. 1972. Obsei-vations on the nesting behavior of Diploplectron peglowi Diploplectron, the sparser setae, head and Krombein. Proc. Ent. Soc. Washington 74: the lack of conspicuous labral sensory 385-397. cones. Parker, F. D. 1972. On the subfamily Astat- inae, Part VII. The genus Diploplectron Fox The larva of Astata feeds in an inverted (Hymenoptera: Sphecidae). Arm. Ent. Soc. position in the cell, the egg having been Amer. 65:1192-1203.