Corresponding author: Peter Schüle (
Academic editor: J. Liebherr
Larvae of all instars of
Schüle P, Putchkov A, Markina T (2021) Larval descriptions of three
The genus
In contrast to adults, information about the larvae is very scarce and larval stages of only two species have been described until now (
This work comprises the descriptions of three species belonging to two different “species groups” of the
The descriptions are based on the following larval material:
The larvae were reared ex ovo in laboratory conditions. The nomenclature follows
Projections of
Head and appendages of
Morphological features of
Morphological features of
In early February 2000, two adults of
The first copulation could be observed during the second day and took only a few minutes, just as all the subsequent copulations. After a few days, the female refused further mating activities by the male. Even if the male’s mandibles successfully gripped the female between the thorax and the elytra (the coupling sulcus being marked by a longitudinal shallow impression on the upper half of the mesepisternum), the male did not succeed in inserting its fully protruding aedeagus. By arrhythmic waggling of the abdomen, the female tried to get rid of the male.
While mating, the male spread out the prolegs, tightly holding the female with its mandibles. The male’s labial palpi, with second palpomeres inflated, flattened and with rows of long setae on the upper surface, were folded backwards and pressed onto the female’s elytra. The use of the male’s dilated protarsi, bearing brush-like adhesive hairs, could not be observed.
Egg laying only took place immediately after watering the substrate. Initially, the female tested the substrate by touching the surface with its palpi, lowering its head while walking slowly. After the female made a small hole by digging with its abdomen, most probably by using its cerci as tools. The abdomen was placed into this hole up to the penultimate tergite, while the ovipositor was extended for ca. 8–10 mm for egg laying.
The first eggs were laid on 6 March. The egg-laying period lasted until the female’s death on 9 June 2000 (95 days later). During this period, the female dug ca. 150 holes. When the female was disturbed by the male, she stopped laying eggs and moved to another area; therefore many holes did not contain any eggs. Furthermore, no larvae left the burrows that had been dug at the end of the egg-laying period.
After hatching, the coiled larvae remained in a small cavity for a few days before digging a circular tunnel to the substrate surface. During the 1st larval instar, the opening of this tunnel was simply rounded. In front of the oblique tunnel opening, the 2nd and 3rd instar dug a transverse cavity, which was larger for the 3rd instar. Sometimes, the tunnel opening was located at the hollowed lateral wall instead of its top. Approximately seventy larvae hatched from eggs and ca. 40 larvae reached the 3rd larval instar (fifteen larvae were killed and added to the second author´s collection). The first larvae could be observed 33 days after the beginning of the egg-laying period. The shortest period between the first instar I larva and the appearance of the instar II larva numbered 21 days while there were 49 days between the first appearance of an instar II larva and the appearance of the instar III larva. After several months, all the instar sizes could be found. In January 2001, seven months after the last eggs had been laid, one specimen of instar I appeared at the surface. In January 2003, the last living instar I larva of the first generation was dug out, 31 months after the last eggs had been laid.
The first pupa was discovered at the beginning of August 2001. The position of the pupa was vertical in a simple cave ca. 1 cm underneath the surface. The first imago of the first generation appeared in September 2001. Several pupae were dug up and placed in a humid box. The hatching of one male was observed: it took ca. 10 hours from the beginning until the elytra were fully developed and another two days for the full coloration to develop. This specimen lived from 31 August to 28 October 2001.
One female was dug up fully developed on the 31 of August. This female started with egg laying 7 weeks later, on 19 October but died on 2 February, after having lived for 5 months. Two eggs with fully developed larvae inside and belonging to the F2 generation were dug up on 6 February. The F2 generation egg mortality was very high, although dozens of eggs were laid, not a single larva hatched.
Morphological features of
The larvae of
Larvae of instars I of
Nevertheless, some other characters (form and chaetotaxy of the head, pronotum, hooks, pygopod) are often similar (or overlapping) in all so far known larvae of
Measurements of head and pronotum with growth ratio of pronotal width/length of
Species | Instars | Measurements in mm, mean in parentheses | ||||
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FL | FW |
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I | 1.25–1.38 (1.29) | 2.05–2.23 (2.14) | 1.18–1.23 (1.20) | 2.08–2.13 (2.12) | 1.73–1.76 |
II | 1.70 | 3.20 | 1.90 | 3.01 | 1.58 | |
III | 2.50–2.70 (2.57) | 4.00–4.40 (4.20) | 2.70–2.90 (2.83) | 4.40–4.75 (4.55) | 1.62–1.64 | |
|
I | 1.05 | 1.80 | 1.05 | 1.85 | 1.76 |
II | 1.40–1.50 | 2.43–2.63 | 1.55–1.73 | 2.65–2.85 | 1. 65–1.70 | |
|
I | 0.8 | 1.35 | 0.95 | 1.50 | 1.58 |
II | 1.17–1.19 | 2.00–2.20 | 1.35–1.40 | 2.05–2.08 | 1,48–1,52 | |
III | 1.70–1.90 (1.80) | 2.80–3.15 (3.01) | 2.05–2.25 (2.14) | 3.40–3.75 (3.59) | 1.66–1.68 | |
|
I | 0.57–0.65 (0.60) | 0.90–1.04 (0.98) | 0.57–0.65 (0.61) | 0.90–1.07 (0.99) | 1.38 |
II | 0.93–0.95 (0.94) | 1.50–1.60 (1.53) | 1.00–1.05 (1.02) | 1.63–1.75 (1.68) | 1.64–1.67 | |
III | 1.30 | 2.25 | 1.48 | 2.58 | 1.75 | |
|
I | 0.85 | 1.48 | 0.95 | 1.58 | 1.66 |
Chaetotaxy of main segments and sclerites of
Species |
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|
|
Tip of |
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9–10 | 2 | 8–10 | 8–10 | 6–8 | 16–17 |
|
11–13 | 2 | 8–10 | 12–16 | 7–9 | 16–17 |
|
10–12 | 1 | 8–10 | 7–9 | 5 | 16 |
We dedicate this article to the memory of the famous coleopterologist Dr. Terry Erwin.
We are very grateful to Lutz Behne (Senckenberg Deutsches Entomologisches Institut, Müncheberg), Michael and Amran Balke (Zoologische Staatssammlung, Munich) and Thierry Deuve (Muséum national d´histoire naturelle, Paris) for their assistance during the second author’s visits to the respective museums, and for loans of type specimens and additional material. We thank Andreas Oesterle (Leutenbach) for providing information about rearing