Current evidence suggests that sexual size dimorphism (SSD) reflects the male and female adaptation to their different reproductive roles. Belostoma and Lethocerus species, included in Belostomatidae, present different kinds of paternal care. Females of Belostoma Latreille species lay their eggs on the back of males. Males carry, aerate and protect the clutch until hatching, which is critical for offspring survival. Males of Lethocerus Mayr species exhibit some parental care behavior but do not carry the eggs. The genera are nearly related. We studied and compared the SSD patterns of B. oxyurum (Dufour), B. micantulum (Stål), B. elegans (Mayr), B. bifoveolatum Spinola, B. gestroi Montandon and Lethocerus annulipes (Herrich‐Schäffer) by means of a multivariate approach to distinguish selection targets in different components of size. Morphometric analysis revealed that SSD patterns vary among traits and that the arrangements are similar in Belostoma species, showing a common trend under resembling selective mechanisms. The widespread SSD trend in insects is that all components of body size are biased towards females, generally related to a fecundity advantage, a pattern now also detected in L. annulipes. We found in Belostoma species that the male has relatively longer middle and hind legs. We propose that SSD in hind legs biased towards males is a selective response for paternal care; they denote a brood‐adapted morphology. The middle leg enlargement may be an associated response to maintain effective locomotion.

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An updated catalogue is given of the cockroach species recorded in Argentina. It includes a list of species, their distribution in the different provinces of the country, the institutions in which the type specimens are deposited, and an updated list of references. The results indicate 87 (plus 2 incertae sedis) species, included in 4 families, 12 subfamilies and 40 currently recognized genera. A few species are widely spread across the country, but 35% (29 + 2 incertae sedis) are only known to occur in Argentina. The biotic affinities of the biogeographic provinces were studied. The data analysis corresponds with the major areas of influence: the Neotropical and Andean regions. A parsimony analysis of endemicity (PAE) was performed. The Parana Forest, Pampa and Chaco biogeographic provinces are supported by numerous endemic species. The families Blaberidae, Blattellidae and Phyllodromiidae include 90% of the species. The cockroach fauna from Argentina is still poorly known and the number of species undoubtedly is higher. The primary homonym of Chorisoneura minuta Rocha e Silva & Aguiar, 1977 was replaced with Chorisoneura rochaesilvae nom. n.

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Growth patterns of Rheumatobates crassifemur crassifemur Esaki and R. bonariensis (Berg) were compared in a multivariate framework. Study of allometric coefficients in R. bonariensis showed sexual differences biased towards males in antennal and foreleg segments and biased towards females in body length and middle-leg segments. Multivariate allometric analysis of female growth patterns detected variation among species in those characters that are strongly modified in males of R. c. crassifemur. We show that sexual morphology diverges as of nymph V in R. c. crassifemur but only in the adults of R. bonariensis.