## 1 Introduction
This knowledge is supported by the observation that species of Drosophila found in arid environments have a complement of hydrocarbons whose chains are longer than those in more temperate climates [27; 28]. In addition to this water retention function, the cuticular compounds serve to protect the insect in several other ways--notably, by providing a barrier to infiltration by insecticides and toxins [29], as well as fungi and bacteria [24]. The hydrocarbons of the cuticle can also convey information via chemical signaling. When one insect encounters another, the cuticular hydrocarbon profile may signal any or all of the following: (i) that the individual is a member of the same species [25]; (ii) of the same colony; (iii) male or female [30]; (iv) caste membership [31]; (v) whether the individual is a close family relation, or a dominant member of the colony attempting to pass along an order, or an inferior member standing by to take a command [32]; and (vi) whether the other insect is fertile and ready to mate, or has already populated [33]. Flies are able to detect cuticular hydrocarbons via the olfactory organs of the maxillary palps and antennae, or by taste, via the organs of the proboscis [28]. Likewise, a constellation of fatty acids and sterols have been isolated from flies, as described by [PERSON] et al. [24; 33; 34]. Free fatty acids ranging between hexanoic acid (6:0) and hexacosanoic acid (26:0) have been described, although many of these are at trace levels in comparison to the dominant palmitic acid, palmitoleic acid, oleic acid, linoleic acid, and stearic acid contributions. Like the hydrocarbons, these lipids are known to provide resistance to desiccation, fungal infection, and bacterial infection. A number of sterols have also been reported, including cholesterol, campesterol, and sitosterol, although cholesterol appears to be the most consistently dominant [35]. As there appear to be qualitative and quantitative differences in the occurrence of these compounds among the various species, the chemical profiles may be useful as a tool for identification and discrimination. Solvent extraction has been the traditional method for the analysis of insect cuticular compounds [24; 26; 36; 37; 38]. The process is straightforward: the insect is placed into a nonpolar solvent, such as methylene chloride, ether, pentane, or hexane, during which time the biological compounds leach into the liquid. Those compounds may then be concentrated and analyzed by gas chromatography-mass spectrometry (GC-MS) or by high performance liquid chromatography (HPLC). Previous work has been done demonstrating the discriminating power of chemical profiles for blow fly larvae and pupae [26; 39; 40; 41; 42]. Headspace solid phase microextraction (SPME) experiments of a single species (_Calliphora vicina_) utilized a polydimethylsiloxane/divinyl benzene/carboxen (PDMS/DVB/CAR) SPME fiber to collect hydrocarbons, fatty acids, and sterols from larvae, and a PDMS/CAR SPME fiber to do the same for pupae [39]. The presence and absence of the compounds were noted and the qualitative data was analyzed by agglomerative hierarchical clustering (AHC). The results in this case indicated that the chemical profiles of larvae and pupae were dissimilar, as were the profiles of pupae of differing ages [39]. The purpose of this project was to interrogate the chemical profiles that could be obtained from pupae by solvent extraction followed by total vaporization solid-phase microextraction (TV-SPME) [43]. The advantage of this method over headspace or immersion SPME is the elimination of the need to determine the optimal organic solvent, and that extracts do not need to be filtered reducing buildup and potential contamination of the GC column. Furthermore, TV-SPME can add additional selectivity and sensitivity based on fiber choice, and requires no changes in instrumentation. Four species of blowfly were investigated: _Cochlionyia macellaria_, _Lucilia cuprina_, _Lucilia sericata_, and _Phormia regina_.