Predation, Development And Reproduction Of The Terrestrail Firefly Pyrocoelia Pectoralis (Coleoptera:Lampyridae)

The terrestrial firefly Pyrocoelia pectoralis Olivier,1883(Coleoptera: Lampyridae) which has been descript as a species distributed in mainland China in the early paper report. However, there was less subsequent research about this species. The field investigation found that the habitats of P. pectoralis distributed in Hubei province. However, the habitat range and the population of this species of firefly decreased year by year due to expansion of construction scope of cities and serious of light pollution. In this paper, we conducted systemic studies on larval predation and development, reproduction of adult in this species in order to provide basic theories and support for further research of protection and utilization of this species of firefly.1. Exploration of predation mechanism of larvaeFunctional structures which were matched with predation behaviors of firefly P. pectoralis were found on the head of larvae in ultra structural observation.The dissection of larvae was conducted to observe the structure of larval digestive tract. Larval gullet was separated into two branches near the ossified structure on base of mandibles and connected with both tubular canals in mandibles, no poison gland was found in larvae. The lethal time of snails Bradybaena. ravida Benson which were injected with the larval midgut extract was significantly shorter than that of other snails which were injected with the extract of larval head and other different parts of digestive tract (p<0.05, df=68). The lethal time of snails which were injected with5mg/ml larval midgut extract (15.96±4.48min) was the most similar with normal predation time of larvae (14.47±2.32min) after comparing lethal time of snails which were injected with different concentrations of midgut extract.In the studies of relationship between firefly P. pectoralis larvae, snail and phorid, high parasitism and lethal rate of snail by phorid was explored. Firefly P. pectoralis larvae could predate the snails which were parasitized but not dead yet. Blood of firefly larvae is a very effective deterrent against phorid and alive larvae could not be parasitized by phorid. 2. Identification of different types of development in P. pectoralisTo explore overwinter rate in the wild population, the field investigation was conducted.847larvae were collected in8habitats around the city of Wuhan and E’zhou. The ratio of overwinter type and non-overwinter type larvae was about1:9. Significant difference was found in sex ratio between overwinter type adults (6:1) and was non-overwinter type adults (1:1).The emergence time of male was found earliest after observed emergency rhythm of larvae which was reared in the lab. There are15days apart from the emergency peak time of males and that of non-overwinter type females. However, it was interesting that the emergency peak time of overwinter type females was perfectly matched with that of males.According to compare the external characteristic value between overwinter type and non-overwinter type adult, the value of body weight, diameter of compound eyes and antenna length of overwinter type males were found significant higher than that of non-overwinter type males (p<0.01). The value of body length, body width, body weight and diameter of compound eyes of overwinter type females were found significant higher than that of non-overwinter type females (p<0.01).3. Larval developmentLarval development under three photoperiods L:D=16:8, L:D=12:12and L:D=8:16at25℃was investigated. The results indicated that larval phase had highly positive correlation with duration of dark period (correlation coefficient V=0.8189). Larval phase under photoperiod L:D=16:8was shortest (119.78±17.45d). Food consumption of larvae had medium positive correlation with duration of dark period (correlation coefficient V=0.6163). Larvae under longer light period pupated much earlier than the one under short light period. No significant differences of overwinter rate of larvae were found under different photoperiods.Larval development at15℃,20℃,25℃,30℃and35℃was investigated under photoperiod L:D=12:12. The results indicated that larval phase decreased while temperature increased. Larvae all died before4th stage at15℃and the larval phase was a little bit longer at35℃than other treatments. The food consumption of larvae increased with the temperature increment while that decreased a little at35℃. Larvae under higher temperature pupated earlier than the one under lower temperature. No significant differences of overwinter rate of larvae were found at different temperatures.The development of overwinter type and non-overwinter type larvae was compared and the results indicated that the differentiation of overwinter type larvae was aroused at3rd stage. The body length, body width, body weight, food consumption and larval phase of overwinter type larvae increased much more than non-overwinter type larvae (p<0.01).4. Comparison of reproductive in different types of adultsRepresentative courtship behaviors of females were found after1day they emerged. No significant difference was found in courtship days and maximum mating time between overwinter type and non-overwinter type females. However, amount of brood eggs, laying eggs and unlaid eggs of overwinter type females were significantly higher than those of non-overwinter females (p<0.01, df=19).Representative courtship behaviors of males were found after6hours they emerged. There is no difference in courtship days between two different types of males but the maximum mating time of overwinter type males were significantly more than that of non-overwinter type males (p<0.01, df=39).The results of mating preference experiments showed that males had no preference in overwinter type and non-overwinter type females. The experiment of mating competition indicated that there is no difference in mating competition ability between overwinter type and non-overwinter type males in very short distance from females. But the time consumption of courtship of overwinter type males was significantly short than that of non-overwinter type males (p<0.01, df=29).In the results of sperm competition experiments, no significant difference was found in fertilization rates between different treated groups but those were significantly lower than fertilization rate of sperm from the males which mated only once.According to compare the amount of laying eggs and hatching rate of eggs in female which mated1,3,5and7times respectively, the regular pattern that the amount of laying eggs was increased with increased mating times which is performed as logarithmic relationship (y=55.3481n(x)+44.225, R2=0.9921) was explored. The hatching rate of eggs had analogical positive correlation with mating times of females and performed as exponential relationship (y=0.3149x0.4675, R2=0.9334).