Euthlastoblatta facies (Walker)

Lu, Wenhua, Valentine, Barry D., Perez-Gelabert, Daniel E. & Gutiérrez, Esteban, 2014, Ecology and Diversity of Cockroaches (Dictyoptera: Blattaria) from the Virgin Islands, Insecta Mundi 2014 (349), pp. 1-32 : 16

13. Euthlastoblatta facies (Walker) ( Fig. 11 )

Blatta facies Walker 1868: 102 ; locality not recorded.

Diagnosis. Adults 9–11 mm, oval, with full tegmina in both sexes; yellowish brown; head pale brown with a narrow dark band between eyes; pronotum pale brown with a dark brown central ‘T’ that is reduced to a transverse band or even absent in a few individuals, and a dark brown medial posterior margin connecting 2 sinuate stripes that are often weakly in touch anteriorly; tegmina almost or completely covering abdomen, pale brown, each with a prominent dark-brown ‘S’ marking that connects anteriorly with the dark sinuate stripe on pronotum; legs all pale; abdomen dark brown with pale lateral margins; cerci flattened, widest in middle, with lateral and ventral but not dorsal setae.

Nymphs similar to adults in having a central but much more distinct dark brown ‘T’ on pronotum; additionally, an inverted ‘Y’ on mesonotum and (less distinct) on metanotum; each notum with a dark brown posterior margin that connects two sinuate, lateral, dark brown stripes, more so on pronotum; like adults, head, thorax, and legs all pale, abdomen dark brown. The dark markings in first instars are grayish, vague, and suggestive. Nymphs can be sorted according to head width categories of 0.5–0.6, 0.7–0.8, 0.9–1.0, 1.1–1.3, 1.5–1.8, and 2.0– 2.3 mm, suggesting six instars (adult 2.3–2.6 mm). A female caught in a Malaise trap during July 2011 carried an oothecum that had tufts of long hairs greater than the length of the abdomen. The sex ratio is about 1:1.

Comments. Euthlastoblatta facies is arboreal and nocturnal; individuals were very active at night on tree trunks and branches but never under ground cover ( Table 1). At least some nymphs of this species are termite runway dwellers; in October 2008 Dr. Barbara Thorne discovered seven nymphs 3–7 mm long in arboreal tunnels of the termite Nasutitermes acajutlae (Holmgren) .

The abundance pattern showed only one high in summer ( Table 2), contrary to other species frequently captured in the forest edge Malaise trap. Abundance was particularly high in 2010 (40 individuals in August, all nymphs) ( Fig. 3 , Table 3), when annual rainfall of prior three years was below 2.0 mm ( Fig. 2 ). Prolonged drought may have induced abundance increase, which was concurrent with the pattern of only one abundance peak each year ( Table 2). However, a spike of 15.8 mm heavy rainfall in November 2003 was followed by a sizable abundance increase in November 2004 ( Fig. 3 ).

A subsequent species, E. absimilis ( Gurney 1937) , was also described from Puerto Rico. According to Princis (1969), both E. absimilis and E. diaphana (Species 12) are distinct from, closely related to, and sympatric with E. facies , suggesting a possible Puerto Rican origin. Roth (1994) first recorded this species from Guana Island, where it is fairly common. It is herein recorded for the first time on St. John of USVI, Great Camanoe, Jost Van Dyke, Little Thatch, Moskito, Necker, Tortola, and Virgin Gorda of BVI, in addition to other previous records on St. Thomas of USVI, Mona Island, Culebra Island, Puerto Rico, Dominica, and Barbados ( Rehn 1932, Princis 1969).

Specimens examined. BDVC —1 nymph, BVI, Great Camanoe Is. , 20.X.2008, S. C. Valentine-Cooper, at night ; 2 males, BVI, Guana Is. , 17-19.X.2000, 1-7.X.2001, B. & B. Valentine ; 2 males, BVI, Guana Is. , 25.X.2003, 30.IX.2005, B. D. Valentine & S. Valentine-Cooper, Malaise trap ; 1 male, BVI, Guana Is. , 14.X.2007, W. Lu, sweep ; 1 male, BVI, Guana Is. , 26.IX.2006, J. Cokendolpher, at UV ; 2 females, BVI, Guana Is., Quail Dove Ghut , 17-23.X.2000, 22-28.X.2001, B. & B. Valentine, Malaise trap ; 2 females, BVI, Guana Is. , 26.IX/ 12.X.2006, B. D. Valentine family ; 11 males, BVI, Guana Is., Quail Dove Ghut , X/ XI.2001, XII.2002, VII /VIII/ IX.2004, VII.2005, XI.2005, II / V / VI / VII / XI.2006, W.-P. Liao, Malaise trap ; 1 female, BVI, Guana Is. , 17.IX.2006, J. Cokendolpher, at UV ; 9 nymphs, BVI, Guana Is., I-II, V, VII, IX, and X ; 1 nymph, BVI, Guana Is. , 26.X.2008, [B. Thorne, in runways of Nasutitermes acajutlae (Holmgren) ] ; 2 adults /1 nymph, Jost Van Dyke, 18-19.X.2010, W. Lu & S. C. Valentine-Cooper; 1 adult, BVI, Little Thatch Is. , 11.X.2010, E. Wright ; 2 nymphs, BVI, Moskito Is. , 25.X.2007, S. C. Valentine-Cooper & W. Lu ; 1 adult /1 nymph, BVI, Moskito Is. , 23.X.2012, E. Hill ; 1 nymph, BVI, Necker Is. , 16.X.2006, S. C. Valentine-Cooper ; 1 nymph, BVI, Necker Is. , 2-5. VI.2005, W. Lu ; 2 adults /3 nymphs, BVI, Necker Is. , 16.X.2010, W. Lu ; 1 male, BVI, Tortola Is. , Sage Mt., 1600-1700 ft., 6.X.2001, B. & B. Valentine. MCZ — 5 adults, BVI, Guana Is., B. & B. Valentine. NMNH — 2 specimens, BVI, Guana Is., 1-6.X.1999, 8.IX-8.X.2000, W. Lu, Malaise trap ; 6 specimens, BVI, Guana Is. , 9.V-9.VI.2000, 9.VIII-8.IX.2000, 8.IX- 9.X.2000, II.2003, W. P. Liao, Malaise trap ; 1 specimen, BVI, Guana Is. , hotel area, 6-13.X.2001, D. E. Perez-Gelabert ; 4 specimens, BVI, Necker Is., 25.X.2000, W. Lu. UDCC —1 nymph, BVI, Guana Is. , 29.X.1997, C. R. Bartlett, beat/sweep ; 1 male, BVI, Virgin Gorda Is. , 11.X.1994, C. R. Bartlett. VIIS — 1 adult, USVI, St. John Is., Lameshur Bay, 18-27. VII.1972, A. Gray .

Figures

Figure 2. Relationship of rainfall (mm) with abundance of all cockroaches captured in a Malaise trap within a forest edge from June 2000 through October 2011 on Guana Island, British Virgin Islands (missing 4 samples of VII/IX.2004, IV.2005, and VII.2007; A: numbers of individuals per month averaged across years; B: numbers of individuals per year averaged across months).

Figure 3. Relationship of average rainfall (mm) with monthly abundance in number of individuals of five cockroach species frequently captured in a Malaise trap within a forest edge from June 2000 through October 2011 on Guana Island, British Virgin Islands (missing 4 samples of VII/IX.2004, IV.2005, and VII.2007).

Figures 8–12. Blattellidae. 8) Cariblatta antiguensis female adult from Tortola Island and nymph from Guana Island. 9) Cariblatta sp. 2 from Tortola Island. 10) Cariblatta sp. 3 from Tortola Island. 11) Euthlastoblatta facies adult and nymph from Guana Island. 12) Nyctibora lutzi adult and nymph from Guana Island (all specimens in BDVC).