Alternative to Critical Point Drying for Soft-Bodied Insect Larvae

Hexamethyldisilazane (HMDS) provides an effective, alternative method to critical point drying in preparing insect larvae for scanning electron microscopy (SEM). Previously, HMDS was considered ineffective for the preparation of soft-bodied larvae because of the impermeability of the integument. Puncturing the integument provides a solution to this problem. Three treatments determined the effectiveness of puncturing and established a protocol for preparing dipteran larvae, as follows: (1) larvae were punctured, dehydrated in an ethanol series, and treated with HMDS; (2) larvae were dehydrated, punctured, and treated with HMDS; (3) (control) larvae were dehydrated and treated with HMDS without puncturing. The 1st approach produced rigid specimens with little surface distortion, and details of the integument were maintained. The 2nd process yielded specimens that were semiflaccid overall but retained some details of the integument. The control treatment produced flaccid specimens that were unsuitable for SEM. Of the 3 treatments, the 1st was the method of choice and used to prepare larvae from 3 other insect orders with similar results. Hexamethyldisilazane provides researchers with an effective, alternative, inexpensive, and easy-touse method for preparing larval specimens.