Diomus seminulus (Mulsant)

F, Guillermo González, Bermúdez, Rodrigo López & Kondo, Takumasa, 2012, First report of Delphastus quinculus Gordon and Diomus seminulus (Mulsant) (Coleoptera: Coccinellidae) feeding on eggs and first-instar nymphs of Crypticerya multicicatrices Kondo and Unruh (Hemiptera: Monophlebidae), Insecta Mundi 2012 (268), pp. 1-6 : 3-4

Diomus seminulus (Mulsant) ( Fig. 3 )

Scymnus (Diomus) seminulus Mulsant 1850: 954 .

Diomus seminulus: Gordon 1999: 151 .

For a complete synonym list see Gordon (1999).

Material studied. (N=2). Colombia: Valle del Cauca, Palmira, Corpoica, Palmira Research Station, 03°30’34”N, 76°19’02”W, 1004 m a.s.l., 28.vii.2010, coll. Rodrigo López B., ex. Feeding on eggs and nymphs inside ovisac of Crypticerya multicicatrices , on undetermined palm, 1 adult male specimen ( CPGG). 1 male voucher specimen in alcohol ( ECCP).

General features. Length: 1.5 to 2.2 mm. Body oval in shape, opaque in color, with thick and conspicu- ous punctuation, especially on elytra. Pilosity decumbent, abundant. Coloration variable, light brown, reddish brown or dark brown, but any of these colors may be combined on pronotum and elytra; some specimens with dark pronotum with margins of a lighter color; elytra may have longitudinal bands of a lighter color compared to margins. Completely jet black specimens are often female. Male genitalia are characterized by having a siphonal apex with a short filament about 1/5 length of sipho, and female genitalia are characterized by having a robust, c-shaped tubular infundibulum ( Gordon 1999).

Note. Examination of the genitalia is crucial for correct identification of the species, since in Colombia there are 45 species known in this genus, many of which could be confused with some of the color morphs of D. seminulus .

(Boyer de Fonscolombe) ( Hemiptera : Aphididae ) on cherry ( Miró and Castillo 2010); “ Aphididae ” ( Gordon 1999); Sipha flava (Forbes) ( Hemiptera : Aphididae ) ( Monteiro et al. 2011a,b,c); and Crypticerya multicicatrices Kondo and Unruh ( Hemiptera : Monophlebidae ) (present study).

Distribution: South America ( Gordon 1999; González 2008).

Biology. Diomus seminulus is quite polyphagous, and is known to feed on mites, aphids, armored scales, whiteflies and now the MFS. Two specimens of D. seminulus were found inside ovisacs of the MFS, feeding on eggs and first-instar nymphs. Monteiro et al. (2011a) studied the longevity and oviposition rate of D. seminulus reared on the yellow sugarcane aphid, Sipha flava , at 24°C, 70 ± 10% relative humidity and 12h photophase. Adult males of D. seminulus were shown to live on average 110.8 days, with a range of 56 to 145 days, whereas adult females lived on average 106.4 days, with a range of 67 to 135 days. The preoviposition period of female beetles was 11 days. On average, each adult female of D. seminulus laid 70.7 eggs during its oviposition period. Peak oviposition occurred between the 20th and 50th day after adult emergence, and during this period 60% of all eggs were laid. Although 25% of the beetle pairs remained laying eggs after this peak, Monteiro et al. (2011a) did not recommend insect rearing at this stage because of the low egg production. Monteiro et al. (2011b) studied the longevity of the larval stages of D. seminulus fed with S. flava in glass containers (1.4 cm diameter and 2.4 cm high), kept in climate chambers at 16, 20, 24 and 28°C, 70 ± 10% relative humidity and 12h photophase. The average total duration of the larval stage decreased as temperatures increased, i.e., 46, 24.4, 16.2 and 14 days at 16, 20, 24 and 28°C respectively; the survival rate of the immature stages was 11, 32, 46 and 28%, at 16, 20, 24 and 28°C respectively; the best rearing temperatures for D. seminulus were 20 and 24°C. At 12 and 16°C, the eggs dried and darkened in color, with a viability of 0% and 29% respectively; egg viability at 20, 24 and 28°C was 67, 98 and 43% respectively; temperatures of 20 and 24°C were the most suitable for egg development ( Monteiro et al. 2011c).

Figures

Figure 3. Diomus seminulus (Mulsant). A–D: habitus; E: Habitus variation; F: male sipho; G–J: male tegmen; K: abdomen; L: female genitalia. Photos by G. González.