MARKING Ceraeochrysa valida (Banks) (NEUROPTERA: CHRYSOPIDAE) LARVAE WITH LIPOSOLUBLE COLORS INCORPORATED IN THE DIET

Abstract

Techniques for marking insects in population studies are used to follow the development of the organisms. For this purpose, dyes must not affect their biology, behavior, or camouflage; such as those utilized in coleopterans, lepidopterans, dipterans, isopterans and hymenopterans. The objective of this study was to evaluate the effectiveness of two liposoluble dyes in marking the neuropteran Ceraeochrysa valida (Banks), and the effect of dyes on the development and survival of larvae and pupae; under the hypothesis that at least one of the two dyes would adequately mark the insects without affecting them for evaluation. The dyes Sudan Red 7B (red) and Sudan Blue 670 (blue) were evaluated mixed in the diet for larvae, plus a not dyed control; 40 recently hatched larvae were used per treatment. The number of marked insects and the duration of the larval and pupal periods were evaluated. This information was analyzed with the Kruskal-Wallis test and the Wilcoxon rank sum test. The percentage of survival as larva, from larva to pupa, and from pupa to adult periods was analyzed with the Chi-square test. All of the larvae were adequately marked with Sudan Blue 670 and 98% with Sudan Red 7B. The duration of the larval and pupal periods presented significant differences (p≤0.0001). Larvae showed a longer period of larval development when they were fed with the red dye (median of 16 d) or blue dye (15.5 d), compared to the control (14 d; p≤0.0004). However, the pupal period was longer with the red dye (13 d) than with the blue dye (11 d; p=0.0003) or the control (11 d; p≤0.0001), with no differences between the latter two (p=0.42). The percentages of survival of larvae, larva to pupa, emergence of adults, or larva to emergence of adult did not show significant differences among treatments (p>0.63). Therefore, Sudan Blue 670 was the dye chosen for the evaluations of C. valida in the field; which gave an unequivocal color to the larvae.