The Mites Associated with Armored Scale Insects

Mutualisms between ants and sap-sucking insects generally involve clear benefits for both partners: the ants provide protection in exchange for honeydew. However, a single ant genus associates with armoured scale insects (Diaspididae) that do not excrete honeydew. We studied three colonies ofMelissotarsus emeryiants from two localities in Mozambique. Vast numbers of the diaspididMorganella conspicuaoccupied galleries dug by the ants under the bark of living trees. Unlike free-livingM. conspicuaand other diaspidids,M. conspicualiving with ants are known to lack shields, likely because they gain protection against enemies and desiccation. Nevertheless, we documented the occurrence of rare individuals with shields inside ant galleries, indicating that their glands continue to secrete wax and proteins as building material. This is likely to constitute a significant portion of the ants’ diet, in addition to diaspidid exuviae and excretions from the Malpighian tubules. Indeed,Melissotarsusworkers cannot walk outside the galleries due to modified middle legs, forcing them to obtain all nourishment within the tree.Melissotarsusfounding queens, however, must locate a suitable host tree while flying, and acquire diaspidid crawlers. This mutualism involves ants that are highly specialised to chew through living wood, and diaspidids that can also live freely outside the bark. It is extremely widespread in Africa and Madagascar, recorded from 20 tree families, and harmful effects on plant hosts require rapid study.

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Heterochromatization and euchromatization of whole genomes in scale insects (Coccoidea: Homoptera)

Development ◽

10.1242/dev.108.supplement.29 ◽

1990 ◽

Vol 108 (Supplement) ◽

pp. 29-34 ◽

Cited By ~ 1

Author(s):

Uzi Nur

Keyword(s):

Scale Insects ◽

Congeneric Species ◽

Maternal Origin ◽

Paternal Origin ◽

Whole Genomes ◽

Armored Scale ◽

Males And Females

In several families of scale insects (coccids), the sex of an embryo is determined by the number of genetically active genomes present (one=males, two=females). In mealybugs (Pseudococcidae), both males and females develop from fertilized eggs but, in the embryos that develop into males, the set of chromosomes (genome) of paternal origin (PG) becomes heterochromatic (H) and genetically inactive and is not transmitted to the offspring. The mechanism that reduces the number of active genomes in male embryos may vary between families and even between congeneric species. Thus, in male embryos of most armored scale species (Diaspididae), the PG is eliminated, while in a few species it becomes H. In two genera of soft scales (Coccidae), males develop from unfertilized eggs when one of two identical genomes of maternal origin becomes H. In most male tissues, one genome remains H. However, in several tissues that become polyploid by endoreduplication, the PG becomes E and genetically active. The tissues in which the PG becomes E often vary between species and the analysis of hybrid males demonstrated that whether the PG becomes H or remains E is determined by the genome of maternal origin. The euchromatization of the PG in the haploid sector of mosaic male embryos and the presence of spermatocytes with two E genomes (instead of one E and one H), following the irradiation of young mealybug males, strongly suggest that the maintenance of the H state requires the presence of a genetically active genome.

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