Allocerus dilaticornis Gory, 1832

(Figs 66–69)

Allocerus dilaticornis Gory, 1832: 384 .

Tropidosoma penniferum Bates, 1870b: 423 .

Remarks. Allocerus dilaticornis was described based on a single female from French Guiana and Tropidosoma penniferum based on a single female from Brazil (Amazonas). Currently, it is known from Peru (Junín), Bolivia, French Guiana, and Brazil (Amazonas) (Monné 2024a; Tavakilian & Chevillotte 2024). According to Monné & Monné (1998), the male of A. dilaticornis is unknown. As well as in the other species of the genus, there is great chromatic variation in males and females of A. dilaticornis; a second male examined has the color as in the female illustrated (Fig. 69). In Cerambycidae, when there is sexual dimorphism in the antennae, it is the males that often have the most modified antennae. In A. bicarinatus (Monné & Monné, 1998) and A. spencei (Kirby, 1818), the antennae in females are somewhat serrate, while they are filiform in males (Fig. 70). However, the antennal shape is the most striking feature that differentiates males from females of A. dilaticornis: antennomeres III–X elongated and not strongly widened (Fig. 67), while they are shortened and strongly widened in females (Fig. 69). Males of A. dilaticornis differ from those of A. spencei (Fig. 70) by the elytra proportionally shorter when compared to prothorax and antennae shorter, slightly surpassing middle of elytra (usually, reaching about posterior sixth of elytra, but could just surpass the middle of elytra in small males of A. spencei). Furthermore, the anterolateral area of the prothorax is distinctly oblique and the anterior margin of the pronotum is distinctly narrower in males of A. dilaticornis . In males of A. spencei, the anterolateral area of the prothorax is rounded and the anterior margin is distinctly wider. Monné & Monné (1998) did not comment on the number of antennomeres in males and females of Tropidosoma Perty, 1832 (now Allocerus). Di Iorio (2003) described the male of A. bicarinatus as having antennae 11-segmented and the female 12-segmented. However, it inverted the sex of the specimens as it is possible to see in the figures: “28-29, Tropidosoma bicarinatum (male) [in fact, female]: 28, dorsal view; 29, ventral view; 29, ventral view … 32-33, Tropidosoma bicarinatum (female) [in fact, male]: 32, dorsal view; 33, ventral view.” Therefore, the description of the male corresponds to that of the female and that of the female to that of the male. The same occurred with the figures of A. spencei in Di Iorio (2003): figs. 26–27 are of a female, not a male; and figs. 30–31 of a male, not a female. Males of Allocerus have antennae 12-segmented and females 11-segmented. Still according to Di Iorio (2003): “ Tropidosoma spencei was recorded by Prosen (1947) from Santiago del Estero: Campo Gallo, but in reality his records are referable to Tropidosoma bicarinatum . The type locality of which is Santiago del Estero: Río Salado (Monné & Monné, 1998). According to Bosq (1949), this label corresponds to Icaño. Monné & Monné (1998) described the male of T. bicarinatum but referred to it as a female (probably a typographic error between the male and female symbols), and the specimen they illustrated (ibid: fig. 1) also is a male.” However, from what can be seen in the photograph of the holotype (Monné & Monné 1998; Bezark 2025), the holotype is actually a female (antennae 11-segmented). Furthermore, the female symbol appears three times in the description of A. bicarinatus, which rules out the possibility of a typographical error.

Material examined. PERU, Loreto (new region record): San Juan de Polis, Rio Momón, 1 male, 14.X.2012, J.J. Ramírez leg. (JJRH) ; Contamana, Rio Ucayali, 1 female, 22.II.2009, J.J. Ramírez leg. (JJRH) ; San Juan de Polis, Rio Momón, 1 male, 16.IX.2024, J.J Ramírez leg. (JJRH) .