The behaviour and breeding biology of the ratflea nosopsyllus fasciatus (Bosc)

Abstract

Various structural and behavioural aspects of the breeding biology of Nosopsyllus fuscia tus (Bosc.) the European rat flea, were studied in the laboratory. 1. Mating is initiated when a contact-chemical stimulus is received by the male maxillary palps. The copulating pair is negatively photdactic. The general pattern of mating behaviour is similar to that found in other Ceratophyllid fleas. 2. The adhesive discs of the male antenna and the sculpturing of the female second abdominal sternite maximise the frictional forces necessary for antennal clasping during copulation. 3. Previous studies of the structure of male flea genitalia are extended by use of the scanning electron microscope, enabling a better understanding of their action. The two penis rods are shown to run one within the other, the inner rod emerging from an aperture in the washer-like end of the outer rod. 4. Exposure to a temporary rise in temperature is shown to be an important factor in mating behaviour and ovarian development. Both sexes normally require a bloodmeal before they will mate, but will mate unfed at temperatures between 30 and 35°C, or if temporarily exposed to this temperature range. A bloodmeal has a longer lasting effect on sexual activity than does a rise in temperature. 5. The mating pheromone is not secreted by unfed male or female fleas but is present on the cuticle of both sexes, when they have recently fed or experienced a temperature rise to 30°C. It is argued that the brief rise in temperature triggers a process of pheromone secretion which continues for several hours after the temperature has fallen. The pheromone is shown to be transient. 6. Chilling below 20°C renders previous attractive females unattractive to males. 7. Females are attractive but non-receptive to males after their first mating. Receptivity cannot be induced again for 72 hours. 8. Females of WV. fuseta us are in the second stage of ovarian maturity at emergence from the cocoon. Ovarian development is further stimulated by a brief exposure to 30°C, put a bloodmeal is necessary for full yolk deposition and for egg laying. Copulation also accelerates ovarian development. 9. The presence of males with the pregnant females stimulates egg productivity. 10. Feeding on the host lasts from two to three hours although it is physically possible for a full bloodmeal to be taken within ten minutes. Sectioning of the rat's skin and observation of behaviour while on the host showed this long period to result partly from the difficulty of stri king a suitable blood vessel and partly from disturbance by the host's grooming. 11. Fleas are killed on areas of the host body which can be reached by its mouth, or which are allogroomed. It is suggested that displacement grooming may have a secondary anti-parasite function. 12. In a single bloodmeal, a female takes about nine times more blood than the male. 13. The adaptations of the larval mouthparts for rasping solid food particles, and for taking liquid faecal blood directly from the imaginal anus are described.