S. Mahunka szerk.: Folia Entomologica Hungarica 28/1. (Budapest, 1975)
to differentiate only upon the basis of size, which was just expected when we consider the morphology of their mouth organs. Larvae in the third stage suck up everything that is smaller than 0.1 mm in diameter. Their single mouth hook helps them 'to take up fibrinous materials. To this end we carried out some measurements to identify the granular size of pig manure (Table 2.). Comparing these to what has been said above it is obvious that even larvae in the third stage are able to take up less than 40 % of the dry weight of the manure . In one of my previous papers I suggested that the obligate coprophagous fly larvae consume ten times as much food as their final weight is during their entire alimentation (PAPP, 1971). The basis for the previous calculations was the length of the alimentary canal being seven times as much as body length and that the inj ested nourishment at 30 °C was discharged some 20 min. later; the same holds in this case, too, nevertheless, the recent findings indicate a smaller figure than the one earlier published. (Length of alimentary canal is 6.2-7.1 times as long as body length - recently taken measurements - the same value for larvae prior to pupation is only 5.22.) Observing the alimentation Fig. 2: The movement of house fly larvae in the case of more than optimal number of larvae (1-7: the situation of the mass of larvae during ontogeny) of larvae under a microscope one seems to conclude that the fine particles and the semiliquid parts of the manure "run through" the animal, i.e. a huge amount is taken up and discharged. Comparing the discharged and the inj ested quantities under hundredfold magnification no difference can be recorded, unfortunately, so far no chemical method has been applied. During our observations we found that perhaps the larvae themselves are unable to distinguish between intact manure and their own di r charges. When, for example, a group of eggs were laid at point No. 1 in Fig. 2 the larvae after hatching stayed in a group and during ontogeny the mass of larvae moved toward yet untouched parts of the manure (2-6). In the case when the quantity of manure was less than optimal the mass of larvae returned to areas where it had already fed (7), i.e. presumable the ate again part of their own discharge. And only after having done this did they leave the breeding place . Such phenomena were frequently observed in the case of larvae of Musca autumnalis DEG. developing in cow pats. This seems to indicate that whenever they can the larvae try to keep away, if possible, from their own discharge.
