|
|
|
|
|
|
|
|
|||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | |||||
Quarterly Journal of Microscopical Science, Vol s2-80, 39-77, Copyright © 1937 by Company of Biologists
1 Department of Entomology, Imperial College of Science and Technology, London
The principal points brought out in the foregoing discussion may be summarized as follows:
1. The points of origin of the anterior, lateral, and posterior labral muscle identify the frons in larval insects.
2. The hypopharynx is proximal to the insertion of the dorsal muscles (when present) of the prementum.
3. The direction of the cardo varies with the prognathous and hypognathous conditions of the insect head.
4. The palpifer is a secondarily demarcated portion of the stipes (Borner and Snodgrass), and cannot be a definite segment of the mouth-part limb, since no muscles take their origin from or are inserted upon it.
5. The lacinia can be recognized by the stipital and cranial flexors, and the galea by the stipital flexor only.
6. The cranial flexor of the lacinia is always retained and is a very important muscle in identifying the single maxillary lobe when one of the two is absent.
7. The origin of the flexors of the lacinia and galea upon the stipes shows that the lobes belong to the stipes.
8. The basal segment of the maxillary palp is often misinterpreted as the palpifer owing to its partial or complete fusion with the basal part of the galea, but it can be definitely identified by the insertion of the palpal muscles upon its base.
9. The premental sclerotization may form two lateral sclerites, but it is never subdivided into a proximal and a distal sclerite.
10. The mentum represents the united cardines of a pair of maxilla-like appendages.
11. The submentum is a derivative of the sternum of the labial segment.
12. The fusion of the submentum and mentum to form a single postmental sclerite is a secondary condition.
13. The sternal muscles of the labial appendages are represented by the premental muscles having their primary origin upon the submentum, and also by the submentomental muscles.
14. With the prognathous condition of the insect head the gula is developed from the cervical membrane.
15. The prognathous insects having a well-developed gula are more specialized than the hypognathous insects in which the gula is either reduced or absent.
16. The larval insects could be classified by the musculature of the mouth-parts, since each group has its characteristic musculature.
