Preliminary Length-Weight Relationship and Cytogenetic Studies of Periplaneta americana (Insecta: Blattodea)

This study was carried out to reveal the length-weight relationship, sex ratio and chromosome number of Periplaneta americana. One hundred specimens of P. americana were collected from different locations around Ekiti State University environment. For sex ratio and the length-weight relationship between male and female P. americana, seventy specimens were examined for sex ratio and length-weight relationship between male and female P. americana, while thirty specimens were observed for cytogenetic study. Meiotic chromosomes of male P. americana were prepared from their testes using standard methods and photomicrographs of the chromosomes were taken. From this study, the sex ratio was 1.3: 1 (male to female), there was no significant difference (P>0.05) after comparing the mean total length and the mean body weight, and also the mean forewing length versus mean body weight. The total length and body weight of male P. americana showed a negative correlation (r=-0.2149) while the females P. americana were positively correlated (r=0.1086) between the total length and body weight. However, negative correlation (r=-0.0412) was also observed between total length and body weight in all the specimens collected. For the forewing length and body weight relationship, a positive correlation was observed in male (r=0.1367), female (r=0.2453) and total population (r=0.5167). Also, the meiotic metaphase chromosome showed 16 bivalents and 1 univalent, although no secondary constitution was observed. Therefore, the total and forewing length of P. americana can be used to determine their weight.