and other Aculeata based on the works of Malyshev. (1917, 1936) and later developed by others authors. (Iwata, 1942; Sakagami and Michener, 1962; Stephen,.
Entomological review 1979, 57 (3): 353–355
A NEW TYPE OF NEST WITHOUT CELLS IN METALLINELLA ATROCAERULEA (HYMENOPTERA, MEGACHILIDAE) V.G. RADCHENKO The present-day classification of the nests of bees and other Aculeata based on the works of Malyshev (1917, 1936) and later developed by others authors (Iwata, 1942; Sakagami and Michener, 1962; Stephen, Bohart and Torchio, 1969), stems from the data yielded by a study of the parts of nests. The cells in which the larvae of bees, bumble-bees and wasps are hatched and fed are the principal part of the nest. The decisive characters in the classifications of nests are the shape of the cells and the materials used for their constructions, and also the position occupied by the cells relative to each other and to the main passage of the nest. The classifications does not correspond to the system of this superfamily, since there are similar types of nests in unrelated groups of bees. The evolution of nesting in the Apoidea is marked by frequent instances of parallelism and convergence. Instances of the construction of nests of different females of the same species are of particular interest. As Fabre noted long ago, the nest is an interaction between the building of the bee and the substrate. Deviations in nesting are most often encountered in members of the Megachilidae (Kerenskiy, 1919; Bonelli, 1968; Descy, 1968; Frich, 1972, etc.). Variation is to be noted both in the shape and size of the cell in some species (Michener, 1964; Parker, 1975) and in the nature of their disposition (Bonelli, 1970). The most interesting deviations in nest construction in the Megachilidae have been established by Krombein (1967) and Michener (1968). It emerges from the work of Krombein that, in addition to normal nests of Megachile policaris, succeeded in observing nests with cells that contained between 2 and 16 eggs in a common mass of pollen; in 5 of the 17 nests found the bees had not constructed rear and side walls of the cell. Michener noted the absence of partitions between cells it half the nests of Heriades spiniscutis which he investigated. He also observed occasional nests with reduced partitions. These facts are evidence that the building instincts of bees are extremely flexible. When studying nest construction in Metallinella atrocaerulea [= Osmia (Chalcosmia) atrocaerulea; Osmia panzeri] we found that cells were completely absent from all the nests investigated. This is a very rare phenomenon for the Aculeata (also known in the Allodapini of the family Anthophoridae). There are no published data on the nesting of the species investigated by us. The species systematically most similar to the species of this genus are members of the subgenus Chalcosmia of the genus Osmia: Osmia coerulescens, which nests in various cavities, including artificial ones, and constructs lineally arranged cells of masticated leaves (Stoeckhert, 1933; Bonelli, 1967; Krombein, 1967; Tasei, 1972, etc.); O.
fulviventris, O. leaiana and O. georgica, concerning which these is only fragmentary information definitely referring to the existence of cells (Verhoeff, 1891; Nielsen, 1901; Krombein, 1967). We give new data on the structure of nests of M. atrocaerulea obtained by the author in various districts in the southeast of the Ukraine (Donetsk, Voroshilovgrad and Zaporozh'ye provinces) in the years 1972-1977 (57 nests containing 376 individuals in various development stages). The nests are constructed as follows. The female seeks out a cavity in timber (formed as a result of the activity of xylophagous insects), choosing one that matches its size (this species varies in size between 6.5 and 12 mm). In all the nests found by us this cavity was an oval passage curving steeply downward and ending blindly (Fig. 1) between 3.5 and 8 cm deep and with a diameter of between 2×3 mm and 3×5 mm. The female does not treat the cavity walls of the future nests in any way and does not cover them at all. Most of the nests were filled with Erysimum canescens pollen (Brassicaceae) slightly moistened with nectar and levelled off in the nest. The food remains loosely packed. The bees had not constructed cells in any of the nests and the pollen masses containing the eggs were not partitioned off in any way. The female simply fills the prepared cavity. * On average the female lays 6.6 eggs in one nest, with a range of from 4 to 12 (the number is mainly dependent on the volume of the cavity). The entrance to the nest is sealed with a plug of masticated leaves. The larvae feed for 23-28 days. By consuming the pollen around itself, a larva clears a cavity for its cocoon. Development of the larvae in a single nest is not simultaneous, i.e. the lower larvae finish feeding and construct cocoons earlier. When the larvae higher up the nest have completely utilized the food around them they construct their cocoons, which rest on the lower ones, and the process continues consecutively from the lowest to the highest. Some larvae in the nest begin to construct their cocoons on several occasions, altering their position. The explanation is that they obstruct each other. As a result the cocoons are randomly arranged in the nest (Fig. 2). The cocoons are cylindrical with oval ends, rather strongly flattened dorsoventrally. There is excrement in the spaces between cocoons, in the area investigated M. atrocaerulea has one generation. *
It is known that females of all species of the Apoidea lay their eggs after the food supplies are ready. Only species of the genus Lithurgus (Megachilidae) lay eggs while building up a store of food (Malyshev, 1930). M. atrocaerulea is similar to Lithurgus in this respect.
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ISSN0013-8738/78/0030-0353$07,50/0 © 1979 Scripta Publishing Co.
Fig. 2. Nest of Metallinella atrocaerulea in timber (longitudinal section) showing formed cocoons
Fig. 1. Nest of Metallinella atrocaerulea in timber (longitudinal section) in the early stage. 1) Pollen; 2) larva; 3) egg; 4) plug.
Let us consider the place of this type of nest in the present-day classification (Stephen et al., 1969). According to this classification, all nests are divided into two groups: those constructed by bees that make a passage leading to the cell (odalous in the terminology of Malyshev, 1936) and those constructed by bees that do not make a passage (anodalous). Nests of the latter group, among which we may also include M. atrocaerulea nests, are subdivided in their turn into a number of types. I. The eggs are laid in a common chamber: a) the progeny are never contained in cells; b) the progeny are ultimately enclosed in separate cell. II. The eggs are laid in separate cells: a) the cells are constructed successively, the cavity(if present) is small and closely surrounded by cells, the material for which is usually collected: 1) the cells are in an open place, usually constructed in groups; 2) the cells are concealed (and closely packed) in a tubular or slit-like cavity; b) the cells are constructed in groups as combs, the cavity (if present) is large and the material for which is usually selected. In accordance with this outline the nest of M. atrocaerulea should be classified as type 1,a. However, this type includes nests of the Allodapini, in which the nature of larval feeding is completely different. It would therefore be appropriate to divide type I, a into two: 1) the progeny receive food repeatedly (Allodapini); 2) the progeny receive all their food at once (M. atrocaerulea).
1) Cocoon; 2) excrement; 3) plug; 4) unfinished cocoon.
It is evident that the type of nest found in M. atrocaerulea develops convergently in some of the Megachilidae. Whereas cells are still constructed in the greater part of the nests of H. spiniscutis and M. policaris and the disappearance of their walls is a traceable process, cells are no longer to be found in M. atrocaerulea. It is rather difficult to explain this phenomenon. One possible way in which nests of such a type could have arisen may be, for example, that the females constructed linear nests with cells fabricated from masticated leaves in cavities. Having begun to utilize cavities of lesser diameter, the bees ceased constructing side walls, since they would have hindered the normal development of larvae. Only the partitions were retained in the nests (nests of this type are known in many Osmia species). Having lost the ability to construct side walls to the cells, the bees began utilize cavities of greater diameter, in which food masses containing eggs could be arranged in several layers, and it became impossible to divide them up by partitions. The cells disappeared completely. There are certain other reasons why partitions may also disappear in cavities of normal diameter (this may be seen with reference to H. spiniscutis nests). The gradual disappearance of all the walls of the cell at the same time is also possible (as is sometimes to be seen in M. policaris). It may be noted that the separation of M. atrocaerulea from the genus Osmia as the independent genus Metallinella on the grounds of morphologically confirmed. The author would like to thank Yu. A. Pesenko for assistance in the preparation of the article. LITERATURE CITED BONELLI, P.B. 1967. Osservazioni biologiche sugli Imenotteri melliferi e predatori della val di
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Fiemme. XIX Contributo. Osmia coerulescens Linne (Hymenoptera – Megachilidae). Studi Trent. Sci. Natur. (Sez.B). 44(1): 30-43. BONELLI, P.B. 1970. Osservazioni biologiche sugli Imenotteri melliferi e predatori della Val di Fiemme. XXXV. Boll. Ist. entomol. Univ. Studi Bologna. 29: 197-206. DESCY, A. 1968. Observations et experiences en vue de modifier le comportement de certains Hyménoptères. Bull. Biol. France et Belgique. 102(4): 391-431. FRISCH, K. VON. 1972. Missglückter Nestverschluss einer Blattschneiderbiene. Rev. Suisse. Zool., 79: 85-88. IWATA, K. 1942. Comparative studies on the habits of solitary wasps. Tenthredo, 4: 1-146. KERENSKIY, I.P. 1919. Two instances of fluctuation in the building instinct of bees. Minutes of meetings of the Natural History Society. University of the Don, 1: 74-76. KROMBEIN, K.V. 1967. Trap-nesting wasps and bees: life histories, nests, and associates. Washington: Smithsonian Inst. Press : 1-570. MALYSHEV, S.I. 1917. On the classification of the nests of bees and wasps. Russk. Entom. Obozr., 18: 1-19. MALYSHEV, S.I. 1930. Nistgewohnheiten der Steinbienen, Lithurgus Latr. (Apoidea). Zeitsch. Morphol. Ökol. Tiere, 19(1): 116134. MALYSHEV, S.I. 1936. The nesting habits of solitary bees. A comparative stady. Eos. 11(3): 201309. MICHENER, C.D. 1964. Evolution of the nests of bees. Amer. Zool., 4(2): 227-239.
MICHENER, CH.D. 1968. Heriades spiniscutis, a bee that facultatively omits partitions between rearing cells (Hymenoptera, Apoidea). J. Kansas Ent. Soc., 41(4): 484-493. NIELSEN, J.C. Biologischen Studien über einige Grabenwespen und Bienen. Allg. Zeitsch. Ent., 6: 113-122. PARKER, F.D. 1975. Nest description and associates of three American bees of the genus "Anthocopa" Lepeletier (Hymenoptera: Megachilidae). Pan-Pacific Ent., 51(2): 113122. SAKAGAMI, S.F. and CH.D. MICHENER 1962. The nest architecture of the sweat bees (Halictinae). Univ. Kansas Press, Lawrence: 1135. STEPHEN, W.P., G.E. BOHART and P.F. TORCHIO 1969. The biology and external morphology of bees with a synopsis of the genera of Northwestern America. Agricultural Exper. Station, Oregon State Univ., Corvallis: 1-140. STOECKHERT, F. 1933.Die Bienen Frankens (Hym., Apid). Beiheft der Deutsch. Ent. Zeitschr., 8: 1-294. TASEI, J.-N. 1972. Observations preliminaires sur la biologie d'Osmia (Chalcosmia) coerulescens L. (Hymenoptera Megachilidae), pollinisatrice de la lucerne (Medicago sativa L.). Apidologie, 3(2): 149-165. TKALCU, B. 1966. Metallinella gen. N. der Familie Megachilidae (Hymenoptera, Apoidea). Acta Entomol. Bohemoslovaca, 63(3): 200-203. VERHOEFF C. 1891. Biologische Aphorismen über einige Hymenopteren, Dipteren und Coleopteren. Verh. natur. Ver. preuss. Rheinl. u. Westf., 48(8): 1-80.
Institute of Zoology, Ukrainian Academy of Sciences, Kiev
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