Survey Methods Development- Identification of T. oleracea larvae and adults.

Larval specimens examined to assess identification procedures were collected in March from turf in several areas in northwestern Washington. Specimens were collected using a variety of random digging (by hand) techniques as well as quantifiable plug-cut sampling methods using a golf hole cutter. Larvae were hand picked from excavated soil or turf roots (while shredding and/or rinsing the root mass in water), then rinsed to remove adhering soil (if needed) and immersed in boiling water for about 60 seconds prior to storage in 80% alcohol.

Identification of the T. oleracea larvae is largely a matter of differentiating between the larvae of T. oleracea and T. paludosa, a process which proved to be problematic and inconclusive in this survey. The similarity of larvae of the two species is reflected in the early attempts to describe the larvae of European crane flies. A 1958 publication, describing the last instar larvae of 36 British Tipulidae crane flies concludes the differences between T. oleracea and T. paludosa larvae "cannot be distinguished" (Criswell, 1958).

A subsequent larval description suggests larvae of the two species can be separated by differences in the shape of ventral projections on the posterior end of the larvae (Brindle, 1960). Illustrations of the key larval structures from that publication, presented here as figures 2 and 3, seem to show distinct differences in the ventral projections, labeled VP (ventral papillae) in figure 2.

However, examination of preserved, field collected late-instar larval specimens found a wide variation in shape of the key structures. Observed variation in shape likely represents naturally occuring variability (possibly including age and larval condition) as well as physical changes due to specimen preparation (rinsing/boiling), preservative (alcohol) induced shrinking, and other handling effects. Some examples of the range of variation observed are presented below (fig.4).

Figure 4. Variation in shape of ventral papillae amon three crane fly larvae.

Due to this variation between specimens and the seemingly subjective nature of species determinations based on this physical character, this identification technique was not applied in this survey. Additional work, possibly involving alternative (standardized) specimen handling techniques and structural analysis, is needed before this character is readily applicable for species identification.