Acta Zoologica Cracoviensia, 11() 1966
The Biology and Morphology of Heterarthrus vagans Fallen (Hymenoptera, Tenthredinidae)
Abstract:
SUMMARY. The results of my experiments and observations carried out on the biology and morphology of Heterarthrus vagans Fall, may be summarized as follows: 1. There are two generations of H. vagans Fall, in a year: a generally scarce spring generation (I) from May to July and a considerably more numerous autumn generation (II) from mid-August to October. 2. Both male and female larvae of generation I go through 5 developmental stadia and have a reduced diapause. 3. Male larvae of generations I and II have 5 stadia. 4. Female larvae of generation II go through 5 or 6 stadia. 5. Pupal instars include two prepupae, I (eonympha) and II (pronympha), and a pupa (pupa libera). 6. Part of prepupae of generation II of the previous year conclude their development and undergo transformation into imagines in the spring of the next year, the others transform into adult insects as late as summer, giving rise to generation II. 7. Arrenotokous parthenogenesis occurs and presumably it is the only way in which males are produced. 8. Females are larger and lighter in colour than males. 9. Females are much more numerous. The ratio of males to females is as 1:4. 10. The size and coloration of insects, the number of antennal segments, and the venation of wings are very variable. 11. The larvae of H. vagans Fall, are monophagous, feed exclusively in the leaves of alder (Alnus), and the mines formed by them are superficial mines of the chamber type, usually eccentrical, more rarely centrical. 12. The main characters differentiating the particular larval stadia are the breadth of head-capsule, the length of body, and the pattern on the body. 13. The structure of larval body exhibits adaptations to its ways of life: the prognathism , the flattening of the body, and the development of dorsal and ventral thoracic suckers. 14. The mine area depends upon the individual characters of the larva and the thickness of leaf. 15. The changes in the mandibles after the last larval moulting are caused by a change in their function. After modification they are used by the larva to construct the cocoon. 16. During the diapause, prepupal survival rate depends on humidity; the lack of moisture is the commonest cause of their high mortality.
