Frolov, A.V. 2000. Descriptions of the Aphodius sticticus Panzer and A. punctatosulcatus Sturm Larvae (Coleoptera, Scarabaeidae). Entomological Review, 80, 769-773.

Original Russian text: Фролов, А. В. (2000) Описание личинок Aphodius sticticus Panzer и A. punctatosulcatus Sturm (Coleoptera, Scarabaeidae). Энтомологическое обозрение, 79, 619–624.

Descriptions of the Aphodius sticticus Panzer and A. punctatosulcatus Sturm larvae (Coleoptera, Scarabaeidae)*

A.V. Frolov

Institute of Zoology, Belarusian Academy of Sciences, Minsk

Abstract

The main morphological features of the larvae of Aphodius sticticus Panzer and A. punctatosulcatus Sturm are described and illustrated.

Material and methods

Larvae were reared in laboratory from the eggs laid by the adults collected on 20.IV.1994 (A. sticticus Panzer) and 2.V.1098 (A. punctatosulcatus Sturm) in vicinity of Ravnopol'e village (Minsk Prov., Pukhovichi Distr.). Egg laying and the growth of the larvae were controlled in order to obtain the larvae of all instars. Altogether were reared: A. sticticus—45 third-instar larvae, 15 second-instar larvae, and 1 first-instar larva; A. punctatosulcatus—24 third-instar larvae, 9 second-instar larvae, and 4 first-instar larvae.

The larvae were treated in the following consecution: 1) killed with ethyl acetate, 2) cleansed in detergent solution, 3) rinsed in distilled water, 4) fixed in Bouen liquid, 5) rinsed in 80% ethyl alcohol, and 6) rinsed in70% ethyl alcohol.

The so treated larvae were preserved in 70% ethyl alcohol. The preliminary treatment of the larvae in ethyl acetate was used to minimize their shriveling and rolling up during fixation. For making the preparations heads of the larvae were cut off and treated with 10% NaOH for 3 hours; then the mouthparts were detached, rinsed in 5% acetic acid and distilled water, and embedded in standard For-Berlese medium. General morphology, colour and chaetom of the head capsule, and spines of the anal sternite were examined in intact larvae in water with stereoscopic microscope MBS-10 in incident light at magnification 16–91x. Preparations were examined with stereoscopic microscope AU-12 in transmitted light at magnification 96–240x. Measurements were taken with microscope graticule. Figures were prepared with microscope cross hairs.

Aphodius sticticus Panzer

Third-instar larva. Head width 1,45–1,56 mm, length 1,04–1,21 mm. Head (Fig. 1) yellowish brown without darker maculae, shining, with indistinct sculpture visible as fine, disorderly wrinkles; sclerites semitransparent. Epicranial suture nearly 2 times shorter than frons. Frontal sutures visible in the form of thin light lines; frequently they are indistinct. Each pleural sclerite with 7 long setae: 4 near basal membrane of antenna, 2 in the center of sclerite, and 1 near epicranial suture; 1 shorter seta nearer to occipital foramen. A few short setae in temporal part without definite number and position. Frons with 10 symmetrically situated setae: 6 setae on anterior part (2 very short medially and 4 relatively long laterally) and 4 short setae situated in a transversal row in the center of the frons.

Aphodius sticticus Panzer, 3-instar larva
Figs. 1–8. Aphodius sticticus Panzer, 3-instar larva. 1—head; 2, 3—mandibles in dorsal view (2—left, 3—right); 4—anal segment; 5—anal sternite; 6, 7—tibia and tarsus (6—anterior, 7—middle); 8—spine of anal sternite.

Clypeus trapezium-like, pale brown, its distal and proximal parts of the same colour, the border between them visible as a dark line. Clypeus with 4 long setae (2 longer laterally and 2 shorter medially) and 2 very short setae on the very lateral margins; the later are indistinct in many individuals.

Labrum three-lobed, its chaetom consists of 28 setae: 16 short and 2 long setae on anterior margin, 2 long setae dorso-laterally, 4 short setae ventro-laterally, 4 setae dorsally (2 short proximally and 2 long distally). Ventral side of labrum with sensitive structures of the epipharynx (Fig. 9).

Mandibles (Figs. 2, 3) subtriangular, asymmetrical; left mandible slightly longer than the right one, its scissorial area broader. Base pale brown, scissorial and molar areas darker, almost black. Lateral sides of each mandible with 3 short setae.

Maxillae (Figs. 10, 11) symmetrical, its chaetom slightly differ in different specimens and on left and right maxillae in one specimen. Cardo with 4 short setae: 2 on ventral side and 2 on lateral side near base of stypes. Ventral side of stypes with a long setae proximally and a short setae distally. Dorsal side of stypes with a row of 8–9 stridulatory teeth and 2 short setae near base of palpifer. Palpifer with 1–2 stridulatory teeth and a seta. Maxillary palpi with 4 segments; 1 seta on segments 1 and 4, 2 setae on segment 3. Galea with a row of 6–8 short setae on ventral side and 5 longer setae on dorsal side and apex; 1 short setae on dorsal side proximally. Dorsal side of lacinia with 5 long and thick setae along medial margin; ventral side with relatively long seta apically. Base of lacinia with 1 short seta dorsally and 1 seta ventrally. Apex of lacinia tridentate.

Legs of different pairs nearly the same in length. Each leg with 36 setae: coxa with 3 setae, trochanter with 7 setae, femur with 11 setae, tibia with 13 setae, and tarsus with 2 setae. Anterior legs differ from others in slightly longer tarsal setae (Figs. 6, 7).

Anal sternite with 25–30 equal, flattened and widened toward apex spines (Fig. 8), not separated into two groups (Figs. 5, 8). Lower anal lobe sinuate in the middle and rounded at sides (Fig. 4).

Second-instar larva differs from the third-instar larva in lesser size: head width 1.04–1.17 mm, length 0.71–1.81 mm.

First-instar larva differs from the second-instar larva in lesser size: head width 0.66 mm, length 0.41 mm.

The larvae of the three Chilothorax Muls. species: A. melanostictus W. Schm. (Maltsev, 1966), A. lineolatus Ill. (Palestrini, Barbero, 1993), and A. distinctus Müll. (Frolov, 1996), are described, the description of A. melanostictus is very short. On the basis of these descriptions and studying the morphology of A. sticticus I could not find a diagnostic character or a set of characters, which would distinguish the larvae of the Chilothorax from the larvae of the other subgenera in Aphodius. The larvae of the four species share pale brown or brown colour of the head, rounded lateral sides of the lower anal lobe, and more or less uniformly situated spines on the anal sternite. The larva of A. sticticus can be separated from the larva of A. melanostictus by the anterior and posterior part of the clypeus (preclypeus and postclyopeus) equal in width and one-colour, whereas the larva of A. melanostictus has the postclypeus narrower and lighter than the preclypeus; from A. lineolatus it can be separated by the lacinia with 5 long setae on dorsal side; from A. distinctus it can be separated by the shape of setae on the anal sternite and galea with 6–8 setae on the dorsal side.

Figs. 9–14. Aphodius sticticus Panzer., A. punctatosulcatus Sturm, 3-instar larva

 

Figs. 9–14. Aphodius Ill. 3-instar larvae. 9–11—A. sticticus Panzer; 12–14—A. punctatosulcatus Sturm; 9, 12—labrum in ventral view; 10, 11, 13, 14—maxilla (10, 13—in dorsal view, 11, 14—in ventral view).

Aphodius punctatosulcatus Sturm

3-instar larva. Head width 2.13–2.00 mm, length 1.55–1.38 mm. Head (Fig. 15)  pale brown, its surface looks mat because of fine, dense granulation. Epicranial suture nearly 2 times shorter than the frons. Frontal sutures visible in the form of thin light lines.

Each pleural sclerite with 8 long setae: 4 near the basal membrane of the antenna, 2 in the center of a sclerite, and 2 near the epicranial suture. A few short setae in temporal part without definite number and position. Frons with 10 symmetrically situated setae: 6 setae on the anterior part (2 very short medially and 4 relatively long laterally) and 4 short setae situated in a transversal row in the center of the frons.

Clypeus trapezium-like (in the examined specimens it is slightly asymmetrical), pale brown (postclypeus slightly paler), with 4 long setae (2 longer laterally and 2 shorter medially) and 2 very short, indistinct setae on the very lateral margins.

Labrum three-lobed, its chaetom consists of 32 setae: 18 short and 2 long setae on anterior margin, 2 long setae dorso-laterally, 6 short setae ventro-laterally, 4 setae dorsally (2 short proximally and 2 long distally). Ventral side of labrum with sensitive structures of epipharynx (Fig. 12).

Mandibles (Figs. 21, 22) subtriangular, asymmetrical; left mandible slightly longer than the right one, its scissorial area broader. Base pale brown, scissorial and molar areas darker, almost black. Lateral sides of each mandible with 3 short setae.

Maxillae (Figs. 13, 14) symmetrical. Cardo with 4 short setae: 2 on ventral side and 2 on lateral side near base of stypes. Ventral side of stypes with long setae proximally and short setae distally. Dorsal side of stypes with a row of 14–18 stridulatory teeth and 2–3 short setae near base of palpifer. Palpifer with 4–6 stridulatory teeth and 1 seta. Maxillary palpi with 4 segments; 1 seta on segments 1 and 4, 2 setae on segment 3. Galea with a row of 11–16 short setae on ventral side and 6 longer setae on dorsal side and apex; 1 short setae on dorsal side proximally. Dorsal side of lacinia with 6 long and thick setae along medial margin; ventral side with relatively long seta apically; base with 2 short setae—1 dorsally and 1 ventrally. Apex of lacinia tridentate.

Figs. 15–22. Aphodius punctatosulcatus Sturm, 3-instar larva
Figs. 15–22. Aphodius punctatosulcatus Sturm. 15—head; 16—anal segment; 17—anal sternite; 18—spine of anal sternite; 19, 20—tibia and tarsus (19—middle, 20—anterior); 21, 22—mandibles in dorsal view (21—left, 22—right).

Legs of different pairs nearly the same in length. Each leg with 39 setae: coxa with 7 setae, trochanter with 7 setae, femur with 11 setae, tibia with 12 setae, and tarsus with 2 setae. Anterior tarsi longer than others, with longer setae. Apices of tarsi distinctly serrate in lateral view. Tarsi, tibiae, and partially femora with small, numerous tubercles (Figs. 19, 20).

Anal sternite with 25–30 equally-shaped, flattened, acute spines in the center. The spines combined into a group, or indistinctly separated by a smooth area into two groups (Figs. 17, 18).  A part of spines in the posterior part of the sternite combined in more or less distinct rows, which are named "palidia" in foreign literature, regardless these spines are similar to the remaining or not (as in the larvae of the species of the subgenus Acrossus). The lower anal lobe partially divided by a longitudinal furrow, its sides slightly sinuate (Fig. 16).

Second-instar larva differs from the third-instar larva in lesser size: head width 1.36–1.43 mm, length 0.90–0.99 mm.

First-instar larva differs from the second-instar larva in lesser size: head width 0.87–0.93 mm, length 0.60–0.64 mm.

The larva of A. punctatosulcatus differs form the larva of another species of the subgenus Melinopterus Muls., A. prodromus Brahm (Madle, 1935, Jerath, 1960), in granulate head and partially mouthparts and legs, and serrate tarsi.

Discrepancy in the descriptions concerning the presence or the absence of the distinct rows of setae on the anal sternite, which is stated by Krell (1997), is probably because of considerable intraspecific variability of this character (which is also found in A. punctatosulcatus), but not because of difference between the European and North-American populations.

References

  1. Mal'tsev I.V. Descriptions of some unknown larvae of scarab beetles (Coleoptera, Scarabaeidae) from Crimea, Entom. Obozr., 1966, vol. 45, no. 1, pp. 144–149.
  2. Frolov A.V. Descriptions of the larvae of Aphodius distinctus (Müll.) and A. scybalarius (F.) (Coleoptera, Scarabaeidae), Entom. Obozr., 1996. vol. 75. no. 3. pp. 577–586.
  3. Jerath M.L. Notes on larvae of nine genera  of Aphodiinae in the United States (Coleoptera: Scarabaeidae), Proc. U. S. Nat. Mus., 1960, vol. 111, pp. 43–94.
  4. Krell F.-T. 6. Uberfamilie: Scarabaeoidea. Nachtrag zur 33. Familie: Scarabaeidae. 14. Gattung: Aphodius Illiger, In: Klausnitzer B. Die Larven der Kafer Mitteleuropas, 1997, vol. 4. Polyphaga, no. 3. pp. 106–123.
  5. Madle H. Die Larven der Gattung Aphodius Ill., Arb. phis. angew. Ent.,1935, vol. 2, no. 4, pp. 289–304.
  6. Palestrini C., Barbero E. Gli stadi preimaginali di Aphodius (Chilothorax) lineolatus Illiger, 1803 (Coleoptera: Scarabaeoidea: Aphodiinae), Elytron, 1993, vol. 7, pp. 49–56.

*Note. After the paper had been published, it was found that the larvae described as those of A. punctatosulcatus in fact belong to A. subterraneus (L.). Apparently it happened that the dung used for rearing A. punctatosulcatus was not treated enough as to eliminate non-targed species. Dung treatment is discussed in some detail in Frolov (2009).