Effect of Duration of Exposure to Males on Female Reproductive Performance of the Green Lacewing, Chrysoperla agilis (Neuroptera: Chrysopidae)

Simple Summary

The effect of duration of exposure to males on female longevity and egg production of the predatory insect Chrysoperla agilis Henry et al. was studied under laboratory conditions. Newly emerged adult females of C. agilis were placed in cages alone or with males, the latter either for 1 week or for the entire females’ lifetime. Females in continuous presence of males laid considerably more eggs than females that had access to males for 1 week. Virgin females lived the longest, and those in the presence of males lived the shortest. Egg hatchability and offspring sex ratio were similar for females exposed to males, irrespective of the duration of exposure. We showed that the presence of one male for 1 week early in the adult life of a female is not sufficient for C. agilis reaching maximum reproduction. Our results are applicable in mass-rearing of C. agilis to be used in biological control against agricultural pests.

Abstract

Chrysoperla agilis Henry et al. is one of the five cryptic species of the carnea group found in Europe. They are known to widely occur in agricultural fields and survive and reproduce in a wide range of temperatures. The reproductive biology of the cryptic species is poorly known, especially regarding the number of matings required for the females’ maximum reproductive output. We recorded the egg production and longevity of virgin females, as well as of females that had access to males for 1 week or for their lifetime. Longevity of C. agilis females with access to males was similar whether these were present for 1 week or for their lifetime (64.8 and 66.1 days, respectively). On the other hand, oviposition was higher in the long-term exposure to males (302.1 vs. 421.1 eggs, respectively). Virgin females lived longer (94.1 days) than mated females and laid a low number (54.5) of (unfertile) eggs. Egg hatchability and progeny sex ratio were similar in treatments with males. Nevertheless, the highest value (0.1321) of intrinsic rate of increase (r_m) was recorded when females were continuously exposed to males. These results are relevant to biological control and could be applicable in mass-rearing C. agilis and predicting its population dynamics in the field.

Selectivity of pesticides used in integrated apple production to the lacewing, Chrysoperla externa

This research aimed to assess the toxicity of the pesticides abamectin 18 CE (0.02 g a.i. L-1), carbaryl 480 SC (1.73 g a.i. L-1), sulfur 800 GrDA (4.8 g a.i. L-1), fenitrothion 500 CE (0.75 g a.i. L-1), methidathion 400 CE (0.4 g a.i. L-1), and trichlorfon 500 SC (1.5 g a.i. L-1) as applied in integrated apple production in Brazil on the survival, oviposition capacity, and egg viability of the lacewing, Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) from Bento Gonçalves and Vacaria, Rio Grande do Sul State, Brazil. An attempt was made to study morphological changes caused by some of these chemicals, by means of ultrastructural analysis, using a scanning electronic microscope. Carbaryl, fenitrothion, and methidathion caused 100% adult mortality for both populations, avoiding evaluation of pesticides' effects on predator reproductive parameters. Abamectin and sulfur also affected the survival of these individuals with mortality rates of 10% and 6.7%, respectively, for adults from Bento Gonçalves, and were harmless to those from Vacaria at the end of evaluation. Trichlorfon was also harmless to adults from both populations. No compound reduced oviposition capacity. C. externa from Vacaria presented higher reproductive potential than those from Bento Gonçalves. In relation to egg viability, sulfur was the most damaging compound to both populations of C. externa. Ultrastructural analyses showed morphological changes in the micropyle and the chorion of eggs laid by C. externa treated with either abamectin or sulfur. The treatment may have influenced the fertilization of C. externa eggs and embryonic development. Sulfur was responsible for malformations in the end region of the abdomen and genitals of treated females. When applied to adults, abamectin, sulfur, and trichlorfon were harmless, while carbaryl, fenitrothion, and methidathion were harmful, according to the IOBC classification.