(Comstock, 1883)
Diagnosis
Scale cover of adult female in life white or yellow, circular, convex, with light brown submarginal exuviae HOWBICL2.jpg , usually concealed under epidermis of hostHOWBICL3.jpg and HOWBICL4.jpg - hence the common name of mining scale. Males are unknown (Davidson and Miller, 1990). Exposed body of adult female greyish brown HOWBICL5.jpg .
Body of slide-mounted adult female membranous initially but developing distinctive transverse stripes of sclerotization across the prosoma, especially on the abdomen, with maturity HOWBIS.jpg . Pygidium with median lobes not zygotic; a pair of gland spines (but no setae) present between median lobes; each median lobe with a club-shaped internal sclerosis arising from the base; and perivulvar pores absent HOWBICP.jpg .
Howell et al., 1986, described and illustrated the first instar nymph of H. biclavis.
Host range
Howardia biclavis is a highly polyphagous species that has been recorded from the bark of woody hosts belonging to 99 genera in 41 plant families (Davidson and Miller, 1990). It is tropicopolitan, but also occurs under glass in temperate zones (Williams and Williams, 1988). Hosts include species of: Acacia, Albizia, Aleurites, Allamanda, Annona spp., Bixa, Camellia, Carica papaya, Chrysophyllum, Citharexylum, Citrus spp., Coffea spp., Cydonia, Ficus, Gardenia, Grevillea, Hibiscus spp., Indigophora, Ixora, Jasminum, Khaya, Litchi, Lycopersicon, Macadamia tetraphylla, Macaranga, Malus sylvestris, Malvaceae, Mangifera indica, Manilkara, Morus, Mundulea, Myristica, Neonauclea, Nephelium, Parinari, Phorodendron, Photinia, Piper nigrum, Plumeria, Prunus spp., Pyrus communis, Punica granatum, Sida, Swietenia, Tabernaemontana, Tamarindus, Terminalia, Trachelospermum and Urena.
Affected plant stages: vegetative growing, flowering and fruiting stages
Affected plant parts: on bark of trunk and branches HOWBICL1.jpg , often under the epidermis HOWBICL6.jpg
Biology and ecology
There is no information available on the biology of H. biclavis, other than that reproduction is by parthenogenesis (Brown, 1965). Crawlers are the primary dispersal stage and move to new areas of the plant or are dispersed by wind or animal contact. Mortality due to abiotic factors is high in this stage. Dispersal of sessile adults and eggs occurs through human transport of infested plant material. This cryptic species usually uses the sharp edges of the pygidial plates to burrow beneath the epidermis of the host before a scale cover is secreted; consequently the scales may be very difficult to see in life (Murakami, 1970).
Economic impact
Danzig and Pellizzari, 1998, describe H. biclavis as a pest in the Palaearctic region. It has been recorded damaging Citrus in Cuba (Grillo and del Valle, 1983).
Detection and inspection methods
Closely examine the bark of trunk and branches for white or yellow, circular, convex scale covers with light brown submarginal exuviae. The scales are usually concealed under epidermis of host and are often extremely difficult to see, appearing as slight bulges on the surface of the host. Sometimes they become more evident if the sample is allowed to dry out.
Natural enemies
Grillo and del Valle, 1983, recorded a eulophid parasite of H. biclavis in Cuba.
Distribution
See Howardia biclavis distribution.
Microscopic examination of slide-mounted adult females is required for authoritative identification to species. In the field, Diaspidiotus juglansregiae could be confused with H. biclavis; but in D. juglansregiae the living female's body is yellow and is usually found on deciduous hosts, whereas that of H. biclavis is not (Gill, 1997).
Comments
Howardia biclavis is a tropical species, probably of African origin, but now occurs almost world-wide (under glass in cooler regions). In spite of records published by Nakahara, 1982, and Danzig and Pellizzari, 1998, H. biclavis is not currently established in the United Kingdom (C.P. Malumphy, Central Science Laboratory, UK, pers. comm.).
Europe
Former Czechoslovakia: under glass (Nakahara, 1982; Danzig and Pellizzari, 1998)
Former USSR: under glass (Nakahara, 1982; Danzig and Pellizzari, 1998)
France: present, no further details (Danzig and Pellizzari, 1998; Foldi, 2001)
Germany: present, no further details (Nakahara, 1982; Danzig and Pellizzari, 1998)
Ireland: present, no further details (Nakahara, 1982)
Italy: under glass (Longo et al., 1995)
Poland: present, no further details (Nakahara, 1982)
Portugal
Madeira: present, no further details (Nakahara, 1982)
Spain
Canary Is: The Natural History Museum collection, London, UK
Sweden: present, no further details (Danzig and Pellizzari, 1998)
Switzerland: present, no further details (Nakahara, 1982)
United Kingdom: present, no further details (Danzig and Pellizzari, 1998)
England: under glass (Nakahara, 1982)
Asia
China
Yunnan: present, no further details (Tao, 1999)
India: present, no further details (Nakahara, 1982)
Karnataka: The Natural History Museum collection, London, UK
Tamil Nadu: present, no further details (CIE, 1957)
Indonesia: present, no further details (Nakahara, 1982)
Java: present, no further details (CIE, 1957)
Japan: present, no further details (Kawai, 1980; Tao, 1999)
Philippines: present, no further details (Nakahara, 1982)
Singapore: present, no further details (Nakahara, 1982)
South-East Asia: present, no further details (Danzig and Pellizzari, 1998)
Sri Lanka: present, no further details (Nakahara, 1982)
Taiwan: present, no further details (Takagi, 1970; Wong et al., 1999)
Africa
Central Africa: present, no further details (Danzig and Pellizzari, 1998)
Egypt: The Natural History Museum collection, London, UK
Ghana: present, no further details (CIE, 1957; Nakahara, 1982)
Kenya: present, no further details (CIE, 1957; Nakahara, 1982)
Madagascar: present, no further details (Nakahara, 1982)
Malawi: present, no further details (CIE, 1957; Nakahara, 1982)
Mauritius: present, no further details (Williams and Williams, 1988)
Rodrigues: present, no further details (Williams and Williams, 1988)
Sao Tomé: present, no further details (CIE, 1957; Nakahara, 1982)
South Africa: present, no further details (CIE, 1957; Nakahara, 1982)
Tanzania: present, no further details (CIE, 1957)
Zimbabwe: present, no further details (CIE, 1957; Nakahara, 1982)
Western Hemisphere
Antigua: present, no further details (CIE, 1957)
Argentina: a very recent record (Claps et al., 2001a)
Buenos Aires: present, no further details (Claps et al., 2001a)
Bahamas: present, no further details (Nakahara, 1982)
Barbados: present, no further details (Bennett and Alam, 1985)
Bermuda: common and widespread (Hodgson and Hilburn, 1991)
Brazil: widely distributed (Claps et al., 2001a)
Bahia: present, no further details (Claps et al., 2001a)
Guanabara: present, no further details (Silva et al., 1968)
Minas Gerais: present, no further details (Claps et al., 2001a Gerais
Rio de Janeiro: present, no further details (Claps et al., 2001a)
Sao Paulo: present, no further details (Claps et al., 2001a)
Central America: present, no further details (Nakahara, 1982; Danzig and Pellizzari, 1998)
Colombia: present, no further details (Nakahara, 1982; Kondo, 2001)
Costa Rica: The Natural History Museum collection, London, UK
Cuba: present, no further details (CIE, 1957; Grillo and del Valle, 1983)
Dominica: The Natural History Museum collection, London, UK
Dominican Republic: present, no further details (CIE, 1957)
Ecuador: present, no further details (Nakahara, 1982)
Galapagos Is: present, no further details (Nakahara, 1982)
French Guiana: present, no further details (Nakahara, 1982)
Grenada: The Natural History Museum collection, London, UK
Guyana: present, no further details (CIE, 1957; Nakahara, 1982)
Jamaica: present, no further details (CIE, 1957)
Mexico: present, no further details (Nakahara, 1982; Miller, 1996)
Montserrat: present, no further details (CIE, 1957)
Panama: present, no further details (CIE, 1957)
Peru: present, no further details (Nakahara, 1982)
Puerto Rico: present, no further details (CIE, 1957)
St Kitts: present, no further details (CIE, 1957)
Trinidad: present, no further details (CIE, 1957)
USA
California: occasionally found in nurseries (Gill, 1997)
District of Colombia: under glass (Nakahara, 1982)
Florida: present, no further details (Nakahara, 1982)
Georgia: present, no further details (Howell et al., 1986)
Hawaii: present on Oahu and Hawaii (Heu, 2002)
Kansas: present, no further details (Nakahara, 1982)
Maryland: present, no further details (Nakahara, 1982)
New York: present, no further details (Nakahara, 1982)
Ohio: present, no further details (Nakahara, 1982)
Pennsylvania: present, no further details (Nakahara, 1982)
Missouri: present, no further details (Nakahara, 1982)
Venezuela: present, no further details (CIE, 1957; Nakahara, 1982)
Oceania
Australia: present, no further details (CSIRO, 2001)
Queensland: present, no further details (CIE, 1957)
Bonin Is: present (Nakahara, 1982; Beardsley, 1966)
Cook Is: present (Williams and Watson, 1988)
Fiji: present (Williams and Watson, 1988)
French Polynesia: present, no further details (Reboul, 1976)
New Caledonia: present, no further details (Williams and Watson, 1988)
New Guinea: present, no further details (Nakahara, 1982)
Niue: present, no further details (Williams and Watson, 1988)
Palau Is: present (Nakahara, 1982; Beardsley, 1966)
Papua New Guinea: present (Williams and Watson, 1988)
Tonga: present (Williams and Watson, 1988)
Truk Is: present (Nakahara, 1982; Beardsley, 1966)
Vanuatu: present (Williams and Watson, 1988)
Wallis Is: present, no further details (Cohic, 1959)
Western Samoa: present (Williams and Watson, 1988)