A Container for Eclosion and Holding Adult Insects Prior to Mass Release

Abstract

The mass release of adult insects requires containers for eclosing pupae and, at times, for holding adults for several days (e.g., Tanaka boxes used in the release of sterile fruit flies illus. in Holler, et al. 1984). These units can be both bulky and expensive. Casual observation of large numbers of confined insects has shown that the majority of their time is spent resting on cage walls or on objects in the cage. The large air volume of a cage is essentially wasted space. With this in mind, a container in the shape of a bag roughly the size of a pillow case was designed for eclosing and holding large numbers of adult braconid parasites. The eclosion bag is mostly walls, takes up little room, and is easy to move about, both within the rearing/eclosion facility and during transportation to release sites. The bags are made from pieces of 32 x 32 nylon mesh screen (Lumite, Inc., Gainesville, GA.) that are sewn together and closed continuously across the bottom and the length of one side by velcro strips. For our purposes, we found that a bag 60 cm wide and 90 cm long was ideal, but smaller as well as larger bags (up to 2m long) have been constructed, and insects have been successfully maintained in them. Earlier designs had rounded edges on the bottom to prevent insects from accumulating in corners and milling. The parasite being held in our research, Diachasmimorpha longicaudata (Ashmead), did not display this behavior to any significant extent, and bags with square-edges proved easier to sew and cheaper to produce. Should these bags be adapted for use with insects in which milling is typically a problem, e.g., tephritid fruit flies, the inclusion of rounded bottom corners might be considered. During the holding/maturation period, parasites were fed a solution of honey and water that was poured into 30 cm polyethylene tubes with an inner diam of 10 mm. The tube ends were closed with 3 cm cotton wicks. The diluted honey seeped through the wick and provided a feeding surface for the insects. To prevent either dripping or incomplete absorbance, we found it necessary to vary the proportions of honey and water with changes in temperature and relative humidity. The tube was held along the upper margin of the bag with a large (#5) binder clip. Cages were then hung from lines, sometimes at two levels in rooms of normal height (2.5 m). An S-hook or open paper clip fitted through the binder clip and then over the line made an effective hanger. Parasitized Caribbean fruit fly pupae (Anastrepha suspensa (Loew)) were poured evenly on the bottom of the bag. A typical volume was 375 ml, which gave rise to approximately 5000 adult parasites. For our needs, adults were maintained in the bags for five days after the first eclosion. They were then taken by vehicle to the release sites. Lines strung in the back of a van provided a convenient method of suspending them during transportation, although bags could be laid flat and stacked several deep with no apparent ill effects on the parasites. At the release site, the feeding tube was removed, the velcro opened, and the pupal remains poured into a bucket. The bag was spread open and shaken in the air. This was a particularly useful technique in releasing D. longicaudata, which have a rela-