Rose Shoot Sawfly - Phylloecus trimaculatus
These pictures have been sitting on my computer for nearly 7 years! Wow, that's a long time to wait for a successful insect identification, and genuinely, I feel silly for how long it took. Especially since I was looking in entirely the wrong places by wrongly assuming it was a variety of Ichneumonid Wasp, due to its overall form and it long, tube-like abdomen. Looking for male Ichneumonids of similar appearance, there were no matches among any of the sources and references I checked. Ultimately, what made identification of this insect more difficult were the photography angles I captured whereby its smoky wings concealed the connection between the thorax and abdomen, and so I was looking for a petiole (wasp-waist) that wasn't there. Moreover, looking closer at Pictures 2 revealed the presence of a short ovipositor (like a black spike) at the bottom of the abdomen's tip, so there's no way that this individual is a male Wasp of any sort. Although I occasionally stumble, stories like this continue to reinforce just how important it is to truly look closely at the insects you find, and from that consider a wider point of view in terms of the possibilities. For the insect in these pictures: since this is clearly a Hymenopteran which lacks a discernable petiole between the thorax and abdomen, it must be a Sawfly, albeit one with a form which is quite unique compared to prior species I've discussed. Mystery solved! The shortened ovipositor with the characteristic "saw" shape also indicates that this individual is indeed a female.
As to this species itself, today's find is a unique branch within the families of the Sawfly "suborder," Symphyta. Specifically, this insect to part of the family Cephidae, or Stem Sawflies, so named because they lay their eggs within plant stems using their saw-shaped ovipositor. The resulting larvae that hatch are stem borers which consume the innards of their host plant as they develop. Suitable plants may include grains, berries, trees, and in the case of this particular species: roses (this is to say, plants in the rose family, not just rose flowers). Naturally, a few species within this family can be considered troublesome pest insects who can jeopardize the growth and/or health of the plants they feed on as the larvae will grow until of substantial size. The larvae will only exit their host plant to overwinter in the soil, and emerge as adults when weather is suitable again. Thusly, we have this adult individual seen here. According to reports around the Rose Shoot Sawfly, adults have typically been spotted in April and remain active throughout the summer, much like this one. Compared to the appearance of other Sawflies, as mentioned above, this species has an overall longer body which is laterally compressed. That is to say that it isn't a perfect cylinder and it is somewhat flattened. In addition, parts of its body are substantially elongated compared to more typical Sawflies. Specifically, their pronotum is quite elongated, they possess longer antennae (at least over 20 segments here), and the aforementioned abdomen is more tube-like and extends past the wings, rather than bulge out. These adaptations could conceivably aid in laying eggs, providing sensory information, or aid in mimicry of Wasps in order to avoid potential predation, but I'm not certain on which is correct. Considering I thought this individual was an Ichneumonid, mimicry seems very likely.
Pictures were taken on June 30, 2019 with a Samsung Galaxy S4. Oh, Happy Earth Day tomorrow by the way.
