Construction of pupal cells by larvae of Aleocharinae (Coleoptera: Stpahylinidae)
1981; The Coleopterists Society; Linguagem: Inglês
ISSN
1938-4394
Autores Tópico(s)Forest Insect Ecology and Management
ResumoLarvae of Aleocharinae spin a silken cocoon for pupation. Many workers have suggested that source of silken material is large median gland found on eighth tergum of larvae of many species. However, it has been found that this gland functions as an in larvae of Oligota oviformis Csy. Observations of pupal cell formation by larvae of Gyrophaena nana Payk. are reported. Larvae shape cells by rearranging substrate material their mandibles. Silken material is secreted from apex of abdomen as a tiny, clear, shining droplet of viscous, colorless fluid which is touched to substrate and drawn out as a thin thread as abdomen is moved. Among other staphylinids, similar cocoons for pupation are produced by larvae of Stenus spp. Most workers who have written about immature stages or life histories of members of staphylinid subfamily Aleocharinae have noted that mature third instar larvae spin a silken cocoon within which they pupate. Paulian (1941) noted that this phenomonon is rather rare within Coleoptera, and 'Topp (1975) suggested that it appeared to be a unique characteristic of Aleocharinae among Staphylinidae. However, mode of construction of cell and source of silken material have been points for speculation. Chamberlin and Ferris (1929) discovered silken cocoons of Liparocephalus brevipennis Maiklin and Diaulota brevipes Casey. They did not find any structure associated production of silk and suggested that a connection may exist between silk production and the curious sac near apex of Presumably they were referring to medial tergal gland on eighth abdominal segment of larvae of these species. Paulian (1941) mentioned several genera of aleocharines which produce a silken cocoon for pupation including Leptusa Kraatz, Microglotta Kraatz, and Cardiola Jacobs. Noting that all of these have a medial tergal gland on eighth abdominal segment, he suggested that this is silk producing gland in species of those genera of aleocharines where it exists. Topp (1973) reported that prepupal larvae of Bolitochara lunulata Paykull spin a silken cocoon, and also (1975) that mature larvae of aleocharine tribe Athetini burrow into litter layer and interstices of soil, spinning there a cocoon into which they weave particles of surrounding substrate. He suggested that tergal gland on eighth abdominal segment of many aleocharine larvae is implicated in widespread ability of larvae of members of this subfamily to spin cocoons. This content downloaded from 207.46.13.16 on Thu, 16 Jun 2016 05:29:19 UTC All use subject to http://about.jstor.org/terms 342 ASHE: STAPHYLINID PUPAL CELLS However, later in same paper he states that eighth abdominal segment of athetine larvae lacks a tergal gland. Badgley and Fleschner (1956) reported that mature larvae of Oligota oviformis Casey pupate less than 1 inch below soil surface within a silken cocoon which they spin with silk secreted by glands located at tip of They do not elaborate further. They stated that glandular process on eighth abdominal tergum which has been proposed as silk producing organ by other authors acts as an in larvae of 0. oviformis. When disturbed, larvae of 0. oviformis are capable of extruding a sac from this process which probably has a protective function and may give off an offensive odor. Moore et al. (1975) confirmed that eighth tergal gland functions as an osmeterium in this species. Kremner (1926) reported that larvae of species of Aleochara Gravenhorst which, when mature, leave puparium of host fly and pupate within a chamber in soil (subgenera Aleochara, Xenochara, Euryodma, and Baryodma) spin a cocoon using threads from anus. In contrast, larvae of species which pupate within host puparium (subgenera Coprochara and Emplenota) coat inside of puparium a substance released from anus, isolating beetle pupa from remains of host pupa and products of defecation. It is not known whether or not substances produced for pupal coverings in these two groups are homologous (Fuldner 1960; Peschke and Fuldner 1977). I have found that mature larvae of all species of Gyrophaena Mannerheim that I have reared (many species) and mature larvae of Phanerota fasciata Say pupate within soil in a silken cocoon into which particles of substrate are incorporated (unpublished observations). I observed pupal cell formation by larvae of Gyrophaena nana Paykull against glass sides of a container into which they had been placed for pupation. The substrate was a mixture of shredded sphagnum moss and sand. All pupal cells observed were between 1 and 2.5 centimeters below surface. Following choice of space between particles of substrate, larva enlarges it by rearranging surrounding substrate particles its mandibles. Formation of pupal cell involved extensive rearrangement of substrate material. The mandibles are used to push, pull, and move bits of substrate from one part of cell to another. In one instance I saw a larva pick a piece of substrate from one wall of cell and press it into opposite wall. I saw many fragments of substrate moved for lesser distances. The larva begins to bind particles of substrate together strands of silk soon after formation of cell begins. The material from which cocoon is woven is secreted from apex of abdomen as a tiny, clear, shining droplet of viscous, colorless fluid. This droplet is touched to surface of substrate by extension of pygopodium and is drawn out as a thin thread as abdomen is moved. The thread is terminated when tip of abdomen is touched to substrate again. Silk strands are usually laid down in a series as tip of abdomen is touched to several spots in succession a side to side motion. Early in cell formation few silk strands are deposited in each series, and deposition of silk alternates periods when larva rearranges substrate material. As pupal cell becomes more ovoid or spheroid, more and more time is spent spinning silk. Finally silk production is constant, and larva weaves a tightly meshed cocoon around itself in center of cell. Observations were terminated This content downloaded from 207.46.13.16 on Thu, 16 Jun 2016 05:29:19 UTC All use subject to http://about.jstor.org/terms THE COLEOPTERISTS BULLETIN 35(3), 1981 343 about 8 hours after pupal cell formation began, when cocoon became so thick that it was impossible to observe activities of larva within it. Production of a silken cocoon for pupation is not limited among staphylinids to larvae of subfamily Aleocharinae as was supposed by Topp (1975). Weinreich (1968) described production of cocoons by larvae of several species of Stenus Latreille (subfamily Steninae). Pupal cell formation by these beetles is surprisingly similar to that described above for larvae of Gyrophaena nana. Larvae of Stenus species produce silk from a secretion from anal opening and deposit it by side to side movements of abdomen. These are only instances known to me of producton of a silken cocoon in Staphylinidae. Value of production of a silken cocoon as a taxonomic character within Staphylinidae is uncertain until more is known about distribution of this character among other groups of Staphylinidae. Comparative studies are also needed of glandular source, composition and method of deposition of this secretion.
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